Association of Clinical Biochemists in Ireland Annual Conference

The value of rapid CSF xanthochromia measurement in diagnosing subarachnoid haemorrhage, a case presentation.

Alastair David Green1, Alison Bransfield1, Darren McLoughlin2, Seán J. Costelloe1

1. Department of Clinical Biochemistry, Cork University Hospital (CUH), Wilton, Cork

2. Emergency Department, CUH.

Background

When investigating subarachnoid haemorrhage (SAH), in the absence of evidence on initial computerised tomography (CT) brain, spectrophotometric analysis of cerebrospinal fluid (CSF) for xanthochromia is recommended (National Clinical Guideline for Stroke for the UK and Ireland (2023)). This case discusses a patient found positive for CSF xanthochromia after the initial CT brain was negative for SAH.

Case

A 41-year-old male presented to the Emergency Department at CUH with sudden onset occipital headache eight days prior while shovelling. The headache was unresponsive to analgesia and associated with vertigo. Vital signs and bloodwork were mostly unremarkable. A CT brain was reported (unverified) as negative for haemorrhage initially. Given the symptoms and high suspicion of SAH, a lumbar puncture was performed, and CSF referred for xanthochromia analysis. The patient had antibiotic cover and referred to the on-call acute medical team. The patient left hospital before treatment was complete and was called to return due to the severity of his condition. Neuroradiology provided a report of subtle subarachnoid haemorrhage on the original CT scan, and he was referred to neurosurgery. A CT angiogram confirmed a 3x4.5mm saccular, bilobed, wide-necked aneurysm arising from the anterior communicating artery, with signs of Vado spasm. He required further intervention under the care of Neurosurgery with Neurovascular interventional radiology. Two days after the initial presentation, the referral laboratory confirmed the presence of xanthochromia in the patient’s CSF specimen, consistent with SAH.

Conclusions

We present a case where the presence of xanthochromia in the CSF specimen was a key determinant in confirming a diagnosis of SAH. Of note is that the patient had left the hospital (before treatment was complete) prior to receipt of formal reports. Had more rapid access to xanthochromia analysis been available on site, the patient may have been diagnosed earlier in his journey.

Assay verification and Paediatric Reference Intervals for High Sensitivity Troponin I and N-terminal pro-B-type Natriuretic Peptide on the Siemens Atellica

Akoji Ameh1, Jennifer J Brady1,2.

1 Department of Clinical Biochemistry, Children’s Health Ireland at Crumlin, Dublin, IRELAND.

2 School of Medicine, University College Dublin, IRELAND.

Background: Cardiac troponin and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are used in paediatric healthcare for the diagnosis and prognostic assessment of many conditions including myocarditis, congenital heart disease, multisystem inflammatory syndrome in children (MIS-C) and heart failure. However interpretation of these markers, which are dynamic throughout childhood is challenging in the absence of method specific reference intervals and 99th percentile cut-offs. The aim of this study was to verify high sensitivity cardiac troponin I (hs-cTnI) and NT-proBNP on the Siemens Healthineers Atellica® immunoassay system and to establish paediatric reference intervals for both assays.

Materials and Methods: Precision, linearity, bias and accuracy were verified according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Reference interval were determined from 404 residual paediatric plasma samples using 2.5th to 97.5th percentiles according to CLSI EP-28-A3c.

Results: Repeatability for hs-cTnI and NT-proBNP respectively were 2.22 – 3.12% and 1.61 – 4.45%, while within-lab imprecision was 2.5 - 9.97% and 5.62 – 6.22 % respectively. Passing-Bablok regression demonstrated good correlations between Atellica IM analysers but showed a positive bias of 20% for NT-proBNP compared to the Roche assay. The reference interval for hs-cTnI for children aged one month to 16 years (n=312, 154 females and 158 males) was 0–17 ng/L with a 99th percentile cut-off of 41 ng/L. The reference interval for NT-proBNP for children aged one month up to one year was 0-969 ng/L (n=21) and for children aged 1 year to 16 years (n=361) was 8–295 ng/L.

Conclusion: Paediatric RI generated in this study for both assays will positively impact on patient care by providing a guide for clear interpretation results, improve accuracy of clinical diagnosis and clinician’s ability to adequately assess cardiovascular conditions in children and adolescents.

Point of Care hCG analysis in early pregnancy

Caroline M Joyce1,2,3,4, Paula M O’Shea5, Rebecca Lynch6, Mark Butler4, David Green4, Seán J Costelloe4, Deirdre Hayes-Ryan1,6, and Keelin O’Donoghue1,2,6

1Pregnancy Loss Research Group, Department of Obstetrics & Gynaecology, University College Cork

2Infant Research Centre, University College Cork, Cork, Ireland

3Department of Biochemistry & Cell Biology, University College Cork, Cork, Ireland

4Department of Clinical Biochemistry, Cork University Hospital, Ireland

5Department of Clinical Biochemistry & Diagnostic Endocrinology, Mater Misericordiae University Hospital, Dublin, Ireland

6Department of Obstetrics & Gynaecology, Cork University Maternity Hospital, Cork, Ireland

Introduction: Human Chorionic Gonadotrophin (hCG) is monitored to aid patient management in early pregnancy. Cork University Maternity Hospital requested access to a Point of Care (POC) analyser for hCG measurement to facilitate movement of their Early Pregnancy Clinic (EPC) to a remote location.

Aim

A mini-verification of two hCG POC analysers, Abbott i-STAT1 and Radiometer AQT90 was performed to guide instrument selection.

Methods

Women attending the EPC who required a hCG blood test for scheduled care were invited to participate in this study. Following informed written consent, an additional lithium heparin blood sample was collected for POC analysis at the clinic visit. Whole blood hCG was measured on the iSTAT-1 analyser in clinic with the remaining sample sent to the laboratory for plasma hCG analysis on the Abbott architect. Residual plasma was frozen at -80oC pending analysis on the Radiometer AQT90 analyser. The AQT90 has a larger hCG measuring range (<2 to >5,000 U/L) than the iSTAT-1 (<5 to >2,000 U/L). Statistical analysis was performed using Analyse-IT software.

Results

A total of 50 women were recruited including women with gestational trophoblastic disease, ectopic pregnancy, miscarriage, and intrauterine pregnancy. Samples with results outside the POC measuring ranges (n=14), although clinically in accord with those of the central laboratory were excluded for the purposes of statistical analysis only. Comparison of the remaining hCG results (n=36) from the iSTAT-1 (whole blood) and Abbott Architect (plasma) showed good agreement across all concentrations using Passing-Bablok regression (y=1.17+0.96x), and correlation (Spearman: r=0.96, p<0.0001). There was also good agreement between the AQT90 and Abbott Architect using Passing-Bablok regression (y=-0.21+1.19x), and correlation (Spearman: r=0.99, p<0.0001).

Conclusions: POC analyser results were clinically concordant with laboratory hCG results making POC a viable alternative. However, a more extensive verification study is required before introducing either POC device into routine clinical use.

Quantifying haemolysis in emergency blood gas analysis using the Helge H10 Hemcheck.

Bourke, J1, Caverley, H2, Costelloe, SJ1

1. Department of Clinical Biochemistry, Cork University Hospital (CUH), Wilton, Cork.

2. Point-of-care Department, CUH.

Introduction

Haemolysis is the preanalytical error most frequently encountered in laboratory medicine, with poor phlebotomy technique the most common cause, particularly in critical care areas. Despite the risk of potentially spurious results, blood specimens for near-patient testing (NPT), including those used at CUH (Siemens RAPIDPoint 500e), are not routinely assessed for haemolysis. This study employs the Helge H10 Hemcheck, a NPT device, to quantify the frequency of haemolysis in blood-gas syringe analyses at the Emergency Department (ED) of CUH.

Methods

Four hundred twenty-five residual blood gas syringes were examined in the ED within 4 hours of phlebotomy. The H10 was configured so specimens with haemoglobin concentrations ≥50 mg/dL were considered haemolysed. Haemolysis frequency in these specimens was defined and compared with rates routinely recorded for ED serum samples in the central laboratory by Beckman Coulter AU5800 analysers. The H10 was previously verified in whole blood serum and plasma at CUH for research purposes.

Results

Ninety-nine of the blood gas specimens (23.3%) were found to be haemolysed. This is significantly higher than the rate of 8% recorded for ED serum samples in 2022 (P<0.05, chi-square).

Conclusion

This study suggests that haemolysis in blood gas syringes may be up to twice as common as in serum or plasma specimens processed in the laboratory. Only through the vigilance of experienced clinicians can results from haemolysed blood gas syringes, such as pseudohyperkalaemia, which do not fit the clinical picture, be identified. Although the H10 might not be practical for routine haemolysis detection in blood gas specimens, it may prove a helpful aid in decreasing haemolysis in the ED through quality-improvement initiatives. Further, since clinicians and patients should expect high-quality and reliable results, technologies to detect haemolysis, such as those used by the H10, may, in the future, become routinely integrated into NPT devices.

A “Gammy”- Looking Plasma Separation

Cullen RE1, Lee GR1,2 & O’SHEA P1,2

1Department of Clinical Biochemistry, Mater Misericordiae University Hospital, Dublin

2School of Medicine, University College Dublin

Introduction

Blood collection tubes (BCTs) with separator gels are commonly used in chemistry laboratories. These inert gels of intermediate density (1.04 g/cm3), form a physical barrier between red cells and serum/plasma using gradient density centrifugation.

We report a case of improper gel separation despite adherence to gel-BCTs manufacturer’s instructions.

Two blood samples collected from a 76yo male with advanced IgA kappa monoclonal gammopathy were received in Sarstedt gel-BCTs for renal profile and Lactate dehydrogenase analysis: S-Monovette® Lithium Heparin and S-Monovette® Serum gel-BCTs respectively. Both samples were centrifuged in accordance with the manufacturer’s instruction, 4000RPM for 10 minutes.

Post centrifugation, it was noticed that the separating gel in the lithium heparin BCT formed the uppermost layer, floating above the supernatant with the plasma remaining in the middle, and the blood cells at the bottom of the tube. The serum gel-BCT demonstrated correct separation of serum and blood cells. Multiple myeloma was suspected to be the likely cause of the inadequate separation in the plasma gel tube. Consultation resulted in reflex testing for serum total protein, albumin and calculated globulin.

Results

Serum: total protein concentration was grossly elevated at 132 g/L (Reference Interval (RI): 63-80 g/L), albumin 25g/L (RI: 35-50 g/L), globulin 107g/L (RI: 26 -39 g/L).

Discussion

The mechanism for inadequate separation in this case is due to the density of the plasma being higher than the density of the separating gel consequent to hyperproteinaemia. Serum was not affected due to the lack of fibrinogen lowering the density, and enabling correct sample separation in this tube type. Failure to identify inadequate separation may lead to analyser probe occlusion or insufficient sample aspiration.

Conclusion

While paraprotein-related assay interferences are well documented, alterations to gel-BCT separation are limited. Multiple myeloma should be considered whenever inadequate gel separation occurs.

The Lows of a Nitrous Oxide High

Cullen R1, Smyth S2,3 and Lee GR1,3

1Department of Clinical Biochemistry and 2Dublin Neurological Institute, Mater Misericordiae University Hospital

3School of Medicine, University College Dublin

Background

In Ireland and internationally, recreational use of inhaled nitrous oxide gas (N2O) has increased dramatically. Currently, N2O is not a controlled substance under Ireland’s Misuse of Drugs Act 1977, due to its legal use for medical, catering and industrial purposes. However under The Criminal Justice (Psychoactive substances) Act 2010, it is illegal to sell N2O for its psychoactive properties but not for its possession. We report a case of a 19 year old male who was diagnosed with N20-induced sub-acute combined degeneration of the spinal cord (N20-SACD), secondary to B12 deficiency.

Case presentation

The patient self-presented to our emergency department (ED) in July 2022, complaining of loss of balance and stiffening of the hands. He showed a broad compensatory gait for his ataxia, Romberg and Babinski response. Biochemical investigations (renal, liver, bone, CK, TFTs) were within normal limits except for a low total B12 (<148 ng/L, RR: 211-760). Second line investigations showed a normal active B12 (63 pmol/L, RR: 33-170), and ceruloplasmin (0.25 g/L, RR: 0.2-0.6) but raised homocysteine, HCys (88 umol/L, RR: 5.5-16.2). MRI showed a high T2 signal in the posterior spinal cord at the level of the mid cervical spine, consistent with SACD. Five days post treatment (IM hydroxocobalamin) his total B12 was (unsurprisingly) elevated (>2000 ng/L) and his HCys levels had normalised (9.3 umol/L). The patient has been referred to neurology and addiction liaison psychiatry services, but unfortunately continues to abuse nitrous oxide and accordingly has re-presented to ED up to four times in the last year.

Conclusion

Abuse of N2O, its colloquial laughing gas, is no laughing matter! Recognition of N2O-SACD and patient’s declaration of N2O arguably supports timely diagnosis and management. Homocysteine appears most useful for biochemical diagnosis and monitoring while other B12 biomarkers (active B12) was potentially misleading.

Verification of the ChloroChek Chloridometer to Facilitate the Implementation of the Macroduct Advanced Sweat test Collection System

Lynch Quinn E, O’Dwyer J, Harvey C, Brennan C, Brady JJ

Department of Paediatric Laboratory Medicine, Children’s Health Ireland at Temple Street, Dublin 1,

Background

Approximately one in every 1,500 infants born in Ireland may have Cystic Fibrosis. Confirmation of a diagnosis of Cystic Fibrosis is made using the quantitative measurement of sweat chloride. Temple Street is one of six centres that perform sweat testing as part of The National Newborn Bloodspot Screening Programme. Temple Street Hospital previously performed sweat testing using the Gibson and Cooke sweat collection method followed by analysis of sweat chloride using a Sherwood chloridometer. We describe the steps involved in the verification of a ChloroChek® chloridometer in order to facilitate the implementation the Macroduct® advanced sweat test collection system.

Methods

The process for sweat collection using the Macroduct® advanced system was evaluated from volunteers. The Chlorochek chloridometer was evaluated using precision, accuracy, linearity and carryover experiments. A reference material comparison study was performed using a series of samples prepared from a Sodium Chloride stock (SRM919b) from the National Institute Of Standards and Technology (NIST).

Results

The Chlorochek chloridometer demonstrated an imprecision of 4.9% for levels less than 30mmol/L and an imprecision of 1.5% at concentrations at the medical decision point. This met specifications for target imprecision as per CLSI Guidelines 34 Ed4 (2019) Sweat testing: Specimen collection and quantitative chloride analysis. The chloridometer showed a bias of ≤1.2% using EQA and ≤2.5% using NIST material, which met our target for bias of <4.3% (CVi x0.33). All sweat test collections performed using the Macroduct® collection system yielded sufficient sweat volume.

Conclusion

The ChloroChek® chloridometer met all predefined analytical targets and was deemed acceptable for routine use. The evaluation of the Macroduct Sweat test collection system yielded no insufficient collections and was considered user friendly and fit for implementation. An audit of our insufficient rate using the Macroduct® sweat test collection system versus the previous Gibson and Cooke method is ongoing.

Title: A National Survey of Laboratory Therapeutic Drug Monitoring Services

Sheehan C., Lee GR., Byrne B.

Dept. of Clinical Biochemistry and Diagnostic Endocrinology, Mater Misericordia University Hospital, Eccles St, Dublin 7

Introduction: Therapeutic drug monitoring (TDM) plays a crucial role in the management of drug therapy and patient care. The overall aim of this survey was to review laboratory TDM services nationwide to determine whether they are contributing optimally to patient management.

Methods: A survey was created within SurveyMonkey and circulated to Irish Clinical Chemistry laboratories. The survey aimed to establish methods in use, therapeutic ranges quoted, and how these compare across laboratories.

EQA reports were also reviewed to indicate where significant differences may be expected, and where ranges were likely to be standardised.

Results: 14 laboratories took part in the survey. The Roche Cobas was the most common manufacturer used for drug measurement (9/14). Significant variations in some quoted TDM ranges were reported. However, survey responses and EQA data suggest methodological differences were unlikely to explain these variations.

The Irish Medication Safety Network (IMSN) Guidelines for lithium state that the minimum effective plasma level for prophylaxis is 0.4 mmol/L, and the optimal level is 0.6-0.75 mmol/L. However, 2/14 labs quote a therapeutic range as low as 0.2 mmol/L and 2 other labs quoted a range as high as 1.2 mmol/L. Methodological differences do not explain these disparities.

The National Institute for Health and Care Excellence (NICE) guidelines recommend a Digoxin TDM range of 0.7 – 2.0 ng/mL. None of the surveyed lab participants quoted this range, and no respondents claimed to have used guidelines to establish their ranges.

Conclusion: Different TDM ranges are quoted for the same drugs in different laboratories.

Differences in methodology do not explain these differences.

Where published TDM guidelines exist, they do not appear to be widely incorporated into the quoted TDM ranges.

Each laboratory should undertake a re-evaluation of the source of their respective TDM ranges to ensure they remain appropriate.

‘Rennies to the Rescue’ – or Maybe Not

Ryan M1, Rasheed E1, Casserly L2

1Dept. of Clinical Biochemistry, University Hospital Limerick.

2Dept. of Renal Medicine, University Hospital Limerick.

Background

Milk alkali syndrome (MAS) is described as a triad of hypercalcaemia, renal impairment and metabolic alkalosis due to ingestion of large amounts of calcium/absorbable alkali. With the introduction of H2 blockers and PPIs, the occurrence of MAS became rare. However, there has been a resurgence of MAS in clinical practice because of the wide availability and increasing use of OTC calcium carbonate, mostly for osteoporosis prevention or indigestion.

Case

We present a case of a 42-yr-old male who presented to his GP complaining of being generally unwell with nausea and intermittent vomiting for the previous 2 months. Blood samples collected at this GP visit showed severe hypercalcaemia (adjusted calcium 3.66 mmol/L) and renal impairment. The critical results were phoned and discussed with the GP. The Consultant Chemical Pathologist advised the GP to refer the patient to the Emergency Department for an urgent medical review.

On admission, he complained of abdominal pain, constipation, polyuria, nausea and vomiting and was found to be hypertensive. No significant past medical history of note.

Laboratory investigations confirmed hypercalcaemia, with appropriately suppressed PTH excluding primary hyperparathyroidism (PHPT). Further work-up to elucidate the cause of non-PTH mediated hypercalcaemia, including 25-OH Vitamin D, 1-25 OH vitamin D, serum ACE, SPEP, PTH-rp, and CT-TAP, were unremarkable. Venous blood gas showed partially compensated metabolic alkalosis.

On further history taking, the patient admitted consuming 5-10 OTC antacid (Rennie) tablets/day for the last two years for ongoing heartburn due to high alcohol intake.

The patient received intravenous fluid resuscitation and zoledronic acid leading to gradual resolution of hypercalcaemia and improvement in renal function.

Conclusion

PHPT and malignancy are the most common causes of hypercalcaemia, but the increasing use of OTC calcium preparations must be carefully considered as part of the differential diagnosis. Critical result communication and advice from the Clinical Biochemistry Department was key to the timely diagnosis and management of this patient.

A Case Study on Paracetamol Toxicity in an Adult with Low Body Weight.

Herbert E.1, Bransfield A 1., Merwick A.2, Costelloe S.1

1.Department of Clinical Biochemistry, Cork University Hospital.

2. Department of Neurology, Cork University Hospital

Background

Paracetamol is the most widely used over-the-counter and prescription analgesic worldwide for acute and chronic conditions. Some patients may be at increased risk of experiencing toxicity at therapeutic doses, particularly those with a low body weight and those with risk factors for hepatotoxicity.

Case Description

A 39-year-old female with Friedreich’s ataxia was admitted to Cork University Hospital for radiologically inserted percutaneous gastrostomy (RIG) tube reinsertion, as it had become dislodged two weeks post insertion. On day six, post-RIG insertion, her blood results included alanine transaminase of 7704 U/L (0-34), aspartate transaminase of 1932 U/L (6-42), alkaline phosphatase of 124 U/L (30-120), international normalised ratio of 1.7 (0.9-1.1), prothrombin time of 16.7 seconds (9.5-11.1). On the same day, the sole paracetamol measurement requested during the patient’s stay was 74.2 mg/L. Paracetamol was stopped, and treatment with N-acetylcysteine (NAC) was administered. The patient had a low BMI of <19 and had declining weight for two years due to progressive dysphagia.

Discussion and conclusion

This patient received paracetamol at a dose of 4 g daily, the maximum recommended for adults on the summary of product characteristics for oral paracetamol. However, according to the British Hepatology Pharmacy Group, the correct dosing was 0.5g rather than 1g of paracetamol four times daily for this patient, as her weight was <40 kg. The elevated paracetamol and liver damage became apparent in her daily bloodwork, so the antidote NAC was promptly given, and the patient subsequently fully recovered. This case demonstrates the importance of collaboration between pharmacy and nutrition in assessing the patient’s weight and other risk factors for hepatotoxicity when prescribing paracetamol. A review of pathways with stakeholders is being pursued at CUH to prevent the recurrence of this phenomenon.

Assessment of haemolysis interference in the Abbott Architect STAT high Sensitive Troponin I assay

MR Cullen, AC Byrne, RE Cullen and GR Lee

Dept. of Clinical Biochemistry and Diagnostic Endocrinology, Mater Misericordia University Hospital, Eccles St, Dublin 7

Introduction

Rejection of haemolysed patient samples for troponin requests risks delays in the urgent diagnosis and management of patients with acute coronary syndrome (ACS). The Abbott Architect STAT high Sensitive Troponin I (hsTnI) package insert reports haemolysis interference of <10% at haemoglobin concentrations of <5 g/L. The aim of this study was to investigate hemolysis interference below and above this level over a range of hsTnI concentrations.

Methods

Six plasma pools ranging from hsTnI concentrations of <5 ng/L to 12000 ng/L were serially spiked with a prepared haemolysate. They were spiked to achieve 8 level of haemolysis, ranging from a haemolysis index (H) of 0 to 12. Every H index of 1 equated to approximately 1 g/L haemoglobin. hsTnI and the H index were analysed on the Abbott Architect i2000sr and c1600 respectively.

Results

There was <10% interference observed up to the highest H index of 12 across all hsTnI concentrations compared to baseline hsTnI concentrations. Also, there was no clinically significant difference between baseline hsTnI concentrations and their spiked counterparts up to the highest H index of 12.

Conclusion

This study has demonstrated minimum interference in the hsTnI assay at higher haemolysis levels reported in the Abbott Architect package insert. Implementing a higher H index threshold into clinical practice will lead to a reduction in rejected urgent hsTnI requests and allow for a timelier follow up in the investigation of ACS.

Groenendijk W1, Kilbane M1, Twomey PJ1, McKenna M2, Purcell Esther1

1. Department of Clinical Chemistry, St. Vincent’s University Hospital

2. Department of Endocrinology, St Vincent’s University Hospital

Title: A Rare Case of Macro-PTH

Background

A 62-year-old woman previously attended another hospital (2021) with muscle weakness and pain. Bloods revealed hypocalcaemia, hypophosphatemia and an elevated parathyroid thyroid hormone (PTH). Secondary hyperparathyroidism and malabsorption were suspected but this was confounded by recent significant weight gain. Patient follow up was in St. Vincent’s Hospital 2023.

Case

Patient presented with a PTH 68.7pmol/L (reference interval 1.6-6.9pmol/L) in the presence of normocalcaemia, adequate Vitamin D levels and normal renal function. Primary and secondary causes of hyperparathyroidism were excluded. The elevated PTH did not fit the clinical picture, and this together with the finding of normal total and ionized calcium indicated potential assay interference.

PTH was measured at St. Vincent’s University Hospital using the Roche Elecys electrochemiluminescence sandwich immunoassay, which uses polyclonal murine antisera. To investigate potential antibody interference, the sample was referred to an independent laboratory for measurement using the Abbott Architect, a chemiluminescent microparticle sandwich immunoassay which uses both goat and bovine antibodies. The PTH result from the Abbott method was 970.5pg/mL (15-68.3pg/mL).

To investigate the presence of macro-PTH, the patient sample was treated with 25% polyethylene glycol (PEG), mixed and centrifuged and PTH re-measured in the supernatant. A comparison sample from a patient with a PTH concentration of 60pmol/L and eGFF<30, and two different IQC samples were also treated with PEG. The recovery of target IQC values and comparison samples in the supernatants varied from 51.1% to 83.7%. PTH in the patient sample post PEG treatment was 3.36pmol/L ((4.89% recovery) taking into account the 1:2 dilution), suggesting that the falsely elevated PTH concentration was caused by a macro-complex.

Conclusion

We report a case of macro-PTH following exclusion of all other causes of an elevated PTH. Although rare, this condition should be investigated when PTH is >4 ULN in the absence of abnormal calcium and renal function.

How to lighten the load of the sunshine vitamin?

C. Cunning, M. MacMahon, P.M. O’Shea, G. R. Lee

Mater Misericordiae University Hospital – Dublin, Ireland

Introduction: Inappropriate test requesting in pathology may be considered for those tests which are either not indicated clinically (i.e. over-utilised) or are under-utilised yet have added value. In attempt to improve test utility, we implemented a consultant-led strategy involving use of a clinical indication form which was effective in controlling requests for vitamin D, B12 and folate in another laboratory within the IEHG (Midlands Regional Hospital, Mullingar) and adopted for other tests (ESR).

Aim: To evaluate the effectiveness of a strategy to support appropriate utilisation of vitamin D.

Methods: General Practitioners (GPs) were given advanced notification of a pre-requisite to complete a Clinical Indication Form (CIF) when requesting Vitamin D analysis, effective of February 2023. Samples were not analysed if this form was absent.

Results: Our strategy resulted in immediate reduction in vitamin D testing (40-53%) over a 7 month period (February to August 2023) compared to the corresponding period in 2022. There was consequent time saving in pre- to post analytical steps (e.g. 66% reduction for sample aliquoting) and cost saving of €21,623. Furthermore, there was a welcomed (modest) decrease (81 to 73%) in the proportion of patients tested who had sufficient vitamin D levels (>50nmol/L), potentially signifying more judicious test requesting. Although increased compliance in use of the CIF (46% up to 74% of requests), ““TATT/fatigue”” was unfortunately mentioned as the sole indication in >50% of CIFs when reviewed at two selected time points (March: 55%, July: 75%), highlighting need for future test rejection in such instances.

Conclusion: The current approach to support appropriate Vitamin D testing shows immediate positive impact but requires longer term review. Electronic data capture would promote further efficiencies, effectiveness and sustainability of this approach which we contend has potential to be adopted for other tests.

Title: Nitrous oxide induced sub-acute combined degeneration of the cord (SACD).

Ciara De Buitléir1 , Patricia E Fitzsimons 1, Caoilfionn Trench1, Margaret O’ Brien2, Mohamed Elsammak1

1Metabolic Laboratory, Department of Paediatric Laboratory Medicine, Children’s Health Ireland (CHI) at Temple Street

2Department of Neurology, Beaumont Hospital, Dublin 9, Ireland.

Case Presentation

An 18-year-old man presented to an adult emergency department with ascending weakness and peripheral neuropathy. There was no previous medical history or pertinent family medical history. Plasma amino acids were requested to investigate a possible metabolic cause.

Results

Plasma amino acid profile showed a significant peak of free homocystine (reference <2 umol/L), low/normal methionine 14 umol/L (reference 10-38). The remainder of the profile was essentially normal. Plasma homocysteine was added (Roche Immunoassay analyser using enzymatic assay) and was significantly elevated at 137 umol/L (reference 3-12).

Urinary organic acids were requested and showed increased excretion of methylmalonic acid [MMA =128 umol/mmol Creat (reference 0 to 8)] with trace methylcitrate but no other propionate metabolites.

The treating physician was contacted. A full history was taken that indicated extensive use of nitrous oxide for recreational purposes, resulting in SACD. The patient was treated with daily IM Vitamin B12 1000mg for 2 weeks, then three times per week.. Following intensive early treatment clinical manifestations significantly decreased and the patient is nearly back to normal.

Conclusion

The recreational use of nitrous oxide has increased, in the last few years, with significant morbidity as illustrated in the case described here.

Nitrous oxide works by inhibiting methionine synthase through depletion of Vitamin B12 stores with resultant significant clinical manifestations that range from peripheral neuropathy to SACD.

Amino acid profile and urine organic acid analysis should be requested in patients in any age presenting with peripheral neuropathy and SACD. This will allow for detection of possible causes of hyperhomocystinemia which includes classical homocystinuria, re-methylation defects, Vitamin B12 and folate deficiency, some cobalamin metabolic defects, some medications (e.g. antiepileptics) and the recreational use of nitrous oxide.

A rare cause of Macrocytosis in an Infant.

Fitzsimons PE1, De Buitléir C1, Trench C1, Cotter M2, Ryan E3, Monavari AA4, 5, 6 and Elsammak M1.

1Metabolic Laboratory, Department of Paediatric Laboratory Medicine, Children’s Health Ireland (CHI) at Temple Street

2Haematology, Department of Paediatric Laboratory Medicine, Children’s Health Ireland at Temple Street.

3Department of Paediatrics, Children’s Health Ireland at Temple Street.

4National Centre Inherited Metabolic Disorders, Children’s Health Ireland at Temple Street.

5 University College Dublin

6 European Reference Network MetabERN

Case Presentation:

A two year old girl presented with hypoglycemia (plasma glucose 2.2mmol/L) and a history of poor oral intake. She was resuscitated with normal saline and dextrose infusion. Clinical examination revealed petechiae. Laboratory investigations were remarkable for positive Sars Cov-2 and mild neutropenia 0.96 X10ˆ9/l (reference 1.0 to 8.5) with marginally elevated MCV 92.3 fl (reference 70-86). Follow up FBC after discharge showed persistent increase in her MCV and delayed milestones (walking, speech and communication skills) noted and metabolic work-up including total homocysteine was performed.

Results:

Urine organic acid analysis showed ketosis reflecting an appropriate response to hypoglycemia. Plasma amino acid profile identified low/normal methionine at 20µmol/L (reference 5 to 77) with a peak of free homocystine. Plasma total homocysteine was increased at 86µmol/L (reference 3-8). Newborn screening results were retrospectively reviewed and confirmed low methionine at 5.8µmol/L. Repeat FBC film review showed macrocytosis. Repeat urine organic acid analysis and dried blood spot acylcarntine profiles were unremarkable [normal methylmalonic acid (MMA) and propionylcarnitine].

The presence of persistently elevated MCV with low methionine raised the possibility of a re-methylation defect due to intracellular cobalamin G/E (CblG/E). Defect in the MTHFR gene was less likely, as it commonly does not present with macrocystosis.

Further investigations included: CSF amino acids, neurotransmitters profiling and cobalamin gene molecular testing. While awaiting results, patient was started on betaine, methylcobalamin and metfolinate. CSF profile was normal apart from undetectable CSF methionine. CSF MTHFR, total and active vitamin B12 and folate were normal. Molecular genetic analysis revealed two pathogenic variants in MTR gene (encoding methionine synthase) confirming cblG.

Conclusion:

Methionine synthetic defects (CblG/E) and CblD-homocystinuria are rare causes of hyperhomocysteinemia syndromes not currently included in the newborn screening panel. Elevated MCV ± MMA in a child with developmental delay warrants exclusion of a cobalamin defect.”

Title: Toxic Alcohols: A Review of calls to the National Poisons Information Centre and Laboratory Testing.

Authors: Conor T Hurley, Edel Duggan

National Poisons Information Centre of Ireland, Beaumont Hospital, Dublin 9

Introduction:

The management of patients with intoxication of Toxic Alcohols (TAs) can be complex. The National Poisons Information Centre (NPIC) are consulted for management advice, particularly when difficulty obtaining a plasma level for Ethylene Glycol (EG) and Methanol is encountered. Before 2019, this testing was carried out in Ireland but has now ceased.

Objective:

To evaluate TA exposures reported to NPIC and analyse if treatment advised is in accordance with the UK toxicological database Toxbase®.

To understand issues being experienced in TA cases by quantifying cases where a sample was sent, issues were experienced, and when deviation from TOXBASE occurred.

Methods:

We identified retrospectively all hospital enquiries to the NPIC about TAs received between 1st January 2019 and 31 May 2023 inclusively. We extracted data on total number of TA calls, number of patients, number of times fomepizole was given, the time it took from hospital admission to obtaining a TA level and that a TA level which complied with Toxbase® guidelines for ceasing fomepizole was obtained.

Results:

The NPIC received 161 Hospital calls regarding 93 exposures in the period observed. Levels were sent for 53 Patients. 18 cases reported issues having samples processed. An estimated timeframe for a result to be received averaged 2.8 days from admission. Fomepizole was administered to 44 patients and was recommended in a further 10 but it was unclear if it was administered. In 7 cases (13%), fomepizole was stopped appropriately and in 21 cases fomepizole was stopped when TA >50mg/L. There were 26 cases where it was not indicated whether a level had been received.

Conclusion:

The results suggest that current Toxbase® guidelines for antidote completion are not being followed in a large number of cases (84%). It also appears that while requested frequently, issues obtaining a level are common.

Lipid targets and dyslipidaemia management in chronic kidney disease within a model 3 hospital.

Authors and Affiliations:

Harris LA a, Murphy F b, O’Hara P a

a Department of Nephrology, Portiuncula University Hospital, Saolta University Hospital Group

b Department of Medicine, Galway University Hospital, Saolta University Hospital Group

Background and Aim:

Patients with Chronic Kidney Disease are at a significantly higher risk of cardiovascular disease.

KDIGO recommends all patients ≥50yo with non-dialysis dependent CKD are prescribed pharmacological lipid-lowering therapy (PLLT). They advise that those 18-49yo with CKD 1-5 not on dialysis with ≥1 of: known CAD; diabetes; previous ischaemic stroke; estimated 10-year incidence of atherosclerotic CVD >10%, be prescribed PLLT.

ADA/KDIGO guidelines recommend all patients with diabetes be prescribed a statin.

This audit aimed to provide an insight into management of dyslipidaemia in patients with CKD within a model 3 hospital.

Methods:

A sample of patients attending the nephrology OPD in PUH were identified for review. Recent documentation and laboratory results were reviewed. Presence or absence of a variety of risk factors were recorded and used to calculate patients’ estimated 10-year risk of ASCVD, per American College of Cardiology formula. Statin use, specific agent and dose were recorded where available.

Results:

Records of 74 patients were reviewed. 50 patients had a diagnosis of CKD and proceeded for inclusion. 68% (34) were female. Mean age was 68 years. CKD 3aA1 was the most frequently identified stage of disease (28%, 14) and renovascular disease was the most prevalent primary aetiology (28%, 14). 66% (33) had lipid profiles recorded.

69% of patients meeting criteria for statin therapy were prescribed a statin.

36% had a diagnosis of type 1 or type 2 diabetes. 83.3% of those diagnosed with DM were prescribed a statin.

Median 10-year risk for ASCVD was 29.6% (IQR:14%-53.2%).

Conclusions:

Patients with CKD attending our service are at high risk of ASCVD. PLLT was under-prescribed in those meeting criteria for treatment. Cost-effective interventions are available for the prevention and management of dyslipidaemia in CKD. Strategies should be considered to improve prescription rates in appropriate patients to reduce their cardiovascular risk.

Title: When Biochemist Becomes Patient.

Author: Dr. Peadar McGing.

Affiliation: Department of Clinical Chemistry and Diagnostic Endocrinology, Mater Misericordiae University Hospital, Dublin 7, Ireland. [Recently retired from]

Abstract:

Introduction: With modern clinical chemistry laboratories churning through thousands of samples each day, it is easy to forget the patient at the other end of the results we produce. This case hopes to inform of a patient’s own story.

Initial Case Presentation: I, the patient and poster author, fortuitously noted a visual field defect in my right eye, formally confirmed three weeks later. A series of neurological examinations, blood tests, and CT scans ruled out a number of potential causes and pointed to a mass in or near the pituitary gland. Laboratory tests included negative pituitary function tests, plus normal CRP and ESR (out-ruled Giant Cell Arteritis). MRI of brain confirmed a mass, possibly craniopharyngioma; referred for neurosurgery.

Surgery: Transsphenoidal excision of cystic suprasellar lesion with nasal septal flap and fascia lata graft closure. Histology: Adamantinomatous Craniopharyngioma, WHO Grade 1. Tumour benign, but has strong tendency to regrow so radiotherapy required.

ITU Post-op Monitoring: The main clinical biochemistry concerns were:

• Diabetes Insipidus (Arginine Vasopressin Deficiency): urine output of >300 mL/h raised alarm but declined after some hours.

• SIADH (Syndrome of Inappropriate Anti-Diuretic Hormone): presented post-discharge.

• Lactate: rose to 3.9 mmol/L but rise was halted by saline infusion.

• Glucose: rose to 14.1 mmol/L and stayed up, eventually requiring insulin injections.

• Potassium and Magnesium: Within reference limits but ITU protocols required me to be supplemented (unpleasant).

SIADH: In a patient presenting with hyponatraemia unexpectedly, SIADH is a diagnosis of exclusion. However, in a patient post-transsphenoidal surgery hyponatraemia is a common late presentation, and in this circumstance SIADH is the usual cause. Out-patient serum sodium three days post-discharge showed level falling from 143 mmol/L to 134 and then to 132. SIADH was diagnosed and fluid restriction (to <750 mL/24h) was instituted successfully.

Outcomes: Tumour successfully removed; full vision restored; extra insights gained.

VERIFICATION OF ANTI-TSH RECEPTOR ANTIBODIES (TRAb) IMMUNOASSAY ON THE ABBOTT ALINITY PLATFORM.

Hutchinson K1, Adam Boyers2, O’Mahony A1, Zakharova A1, Louw M1

1. Eurofins Biomnis, Sandyford, Dublin 18, Ireland

2. School of Biological, Health and Sport Science, Technological University Dublin

Background

Thyroid Stimulating Hormone Receptor Antibodies (TRAb) determination is crucial for the etiological diagnosis of Graves’ Disease (GD), the most common cause of hyperthyroidism. The circulating TRAb correlate with disease severity and are a useful prognostic biomarker for GD. From 2020 the number of requests for this test increased by over 50% in our Laboratory. All samples were referred to Eurofins France for testing. The objectives of this study were to perform laboratory evaluation of Abbott TRAb assays on Alinity system in Eurofins Ireland and to verify the manufacturer’s reference interval (RI) in the Irish population.

Materials and Methods

Serum samples from 136 patients were obtained from several Irish hospitals in compliance with “Guidance on Anonymisation and Pseudonymisation”, June 2019. 31 samples were analysed for method comparison between Abbott Alinity chemiluminescent microparticle immunoassay and Roche electrochemiluminiscent immunoassay anti-TSH-R method run on a COBAS 6000 auto-analyser. 120 samples from healthy individuals were analysed in order to verify the RI proposed by the manufacturer. Method comparisons and statistical analysis were performed on EP Evaluator 11.3.0.23 software.

Results

Semi-quantitative method comparison of the Alinity and Cobas TRAb methods showed a high agreement of 93.5%, with a high Cohen’s Kappa of 80.1%. Method comparison also passed the McNemar test for symmetry (p=0.50). Alternative method comparison revealed a positive bias of 0.457 (12.55%) for the Alinity method, with a r=0.99 and a slope=1.12. A RI was successfully verified on healthy individuals, with a proposed RI of <1.99 IU/L. An uncertainty of measurement was calculated as 0.11 at 9.92 IU/L (1.14%).

Conclusion

The Abbott Alinity TRAb assay showed high agreement with the Roche Cobas TRAb method at Eurofins France. The success of this study eliminates the need for TRAb samples referrals, improving turnaround times, increasing cost-effectiveness, and providing more timely diagnoses of Graves’ disease in Ireland.

Title: Vitamin D insufficiency correlates with decreased levels of active folate in postpartum women in spite of folate supplementation

Authors: Pooja Dhiman, Soundravally Rajendiran, Raji R Pillai

Abstract

Background

Vitamin D has been shown to affect folate levels by modulating its intestinal absorption in animal studies. We aim to analyze the effect of circulating vitamin D levels on plasma 5-methyl tetra hydro folate (5-methyl THF), the active form of folate in circulation, in folate-supplemented women in their postpartum period.

Methodology

434 women at 6 weeks post-delivery were recruited in the present study. The venous sample was collected in EDTA vials, and plasma was immediately separated and stored at -80C for further analysis. Commercially available ELISA kits estimated plasma 25-OH vitamin D and 5-methyl THF. The normality of the data was checked by the Shapiro-Wilk test using the SPSS version. As the data were non-normal in distribution, log-transformed values were used to perform linear regression in order to observe the relationship between 25-OH vitamin D and 5-methyl THF. In addition, the whole cohort was divided into three groups based on circulating 25-OH vitamin D levels – optimal (25-80ng/ml), mild to moderate deficiency (10-24ng/ml), and severe deficiency (<10ng/ml). The difference in 5-methyl THF levels was observed in three groups using the Kruskal-Wallis test.

Result

25-OH vitamin D and 5-methyl THF were significantly related to each other (β=0.109; p = 0.002). Also, significantly lower levels of 5-methyl THF were observed in mild-moderate vitamin D deficiency when compared to the women with optimal vitamin D (p = 0.004; Figure 1).

Conclusion

Therefore, in folate-supplemented women, vitamin D positively influences the folate level in circulation.

A case of possible heterophile antibodies interference in CA19-9 Abbott Alinity immunoassay

Byrne E¹, Al-Hasani W¹, Sardiwal, S¹, Lister A¹, Iqbal M¹, Mudunkotuwa S¹, Hampson, G¹, Wierzbicki, AS¹.

¹Dept Clinical Biochemistry, (Synnovis), Guy’s and St Thomas’ Hospital, London SE1 7EH, UK.

Background

Cases of heterophilic antibody interferences with the Abbott Architect i2000 CA19-9 immunoassay versus the Roche Cobas Elecsys and Siemens Advia Centaur CP CA19-9 immunoassays have been reported in the literature. We report a case of a possible heterophile antibodies interference in the Abbott Alinity CA19-9 immunoassay.

Case

A 70-year-old male was diagnosed with inoperable advanced squamous/adeno-squamous carcinoma of the head of the pancreas in May 2022. His pre-treatment CA19-9 result was 1110 kU/L (Roche Elecsys Immunoassay, reference interval 0 – 27 kU/L). He commenced 6 cycles of FOLFIRINOX chemotherapy and showed a good response (CA19-9 dropped to 18 kU/L in August 2022), therefore continued treatment. In November 2022, Guy’s & St. Thomas’ Hospital Trust Clinical Biochemistry laboratory changed from Roche Cobas to Abbott Alinity analytical platforms. Verification studies showed a positive bias for the Abbott Alinity CA19-9 assay versus the Roche assay (13 % for values ≤1200 kU/L, 134 % for values >1200 KU/L). Dual reporting of results for 6 months was agreed following the change. On completion of treatment, the patient’s CA19-9 on the Roche assay was 39 kU/L and the concordant first result on the Abbott Alinity assay was 6248 kU/L. Polyethylene glycol (PEG) precipitation was performed on the sample and it was reanalysed. The post-PEG CA19-9 concentration decreased from 6248 kU/L to 66 kU/L on the Abbott Alinity assay but there was no observed difference when analysed by Roche assay. This confirmed that the discordant result was most likely due to a heterophilic antibody interference.

Conclusion

Heterophilic antibodies are a still a potential source of interference in immunoassays. In this case, dual reporting revealed a significant analytical interference that otherwise may have resulted in unnecessary anxiety and further investigations. Suspected discordant results should be escalated for further analytical investigations to avoid any potential impact on patient management.