Volume 55, Issue 1

In recent years it has been shown that vitamin D deficiency is associated with an increased incidence as well as the progression of a broad range of diseases including osteoporosis, rickets, cardiovascular disease, autoimmune disease, multiple sclerosis and cancer. Consequently, requests for the assessment of vitamin D status have increased dramatically. Despite significant progress in the analysis of vitamin D metabolites and an expansion of our pathophysiological knowledge of vitamin D, the assessment of vitamin D status remains a challenging and partially unresolved issue. Current guidelines from scientific bodies recommend the measurement of 25-hydroxy vitamin D (25-OHD) in blood as the preferred test. However, growing evidence indicates significant limitations of this test, including analytical aspects and interpretation of results. In addition, the relationships between 25-OHD and various clinical indices, such as bone mineral density and fracture risk, are rather weak and not consistent across races. Recent studies have systematically investigated new markers of vitamin D status including the vitamin D metabolite ratio (VMR) (ratio between 25-OHD and 24,25-dihydroxy vitamin D), bioavailable 25-OHD [25-OHD not bound to vitamin D binding protein (DBP)], and free 25-OHD [circulating 25-OHD bound to neither DBP nor albumin (ALB)]. These parameters may potentially change how we will assess vitamin D status in the future. Although these new biomarkers have expanded our knowledge about vitamin D metabolism, a range of unresolved issues regarding their measurement and the interpretation of results prevent their use in daily practice. It can be expected that some of these issues will be overcome in the near future so that they may be considered for routine use (at least in specialized centers). In addition, genetic studies have revealed several polymorphisms in key proteins of vitamin D metabolism that affect the circulating concentrations of vitamin D metabolites. The affected proteins include DBP, 7-dehydrocholesterol synthase and the vitamin D receptor (VDR). Here we aim to review existing knowledge regarding the biochemistry, physiology and measurement of vitamin D. We will also provide an overview of current and emerging biomarkers for the assessment of vitamin D status, with particular attention methodological aspects and their usefulness in clinical practice.

It has been well reported over recent years that most errors within the total testing process occur in the pre-analytical phase (46%–68.2%), an area that is usually outside of the direct control of the laboratory and which includes sample collection (phlebotomy). National and international (WHO, CLSI) guidelines recommend that the order of draw of blood during phlebotomy should be blood culture/sterile tubes, then plain tubes/gel tubes, then tubes containing additives. This prevents contamination of sample tubes with additives from previous tubes that could cause erroneous results. There have been a number of studies recently looking at whether order of draw remains a problem with modern phlebotomy techniques and materials, or it is an outdated practice followed simply because of historical reasons. In the following article, the European Federation of Clinical Chemistry and Laboratory Medicine Working Group for the Preanalytical Phase (EFLM WG-PRE) provides an overview and summary of the literature with regards to order of draw in venous blood collection. Given the evidence presented in this article, the EFLM WG-PRE herein concludes that a significant frequency of sample contamination does occur if order of draw is not followed during blood collection and when performing venipuncture under less than ideal circumstances, thus putting patient safety at risk. Moreover, given that order of draw is not difficult to follow and knowing that ideal phlebotomy conditions and protocols are not always followed or possible, EFLM WG-PRE supports the continued recommendation of ensuring a correct order of draw for venous blood collection.

The Health Technology Assessment (HTA) is a multi-professional and multidisciplinary evaluation approach designed to assess health technology in the broadest sense of the term, from its instruments to the rearranging of its organizational structures. It is by now an established methodology at national and international levels that involves several medical disciplines thanks to its versatility. Laboratory medicine is one of these disciplines. Such specialization was subjected, in recent years, to deep changes even from an organizational standpoint, in order to meet the health needs of the population, making them as effective and cost-effective as possible. In this regard, HTA was the tool used to assess implications in different areas.

Background: The long noncoding RNAs (lncRNAs) have gradually been reported to be an important class of RNAs with pivotal roles in regulation of gene expression, and thus are involved in multitudinous human complex diseases. However, the biological functions and precise mechanisms of the majority of lncRNAs are still poorly understood. Methods: In the study, we tested genomic variations in lncRNA-metastasis-associated lung adenocarcinoma transcript 1 ( MALAT1 ) loci, and their potentially functional correlationship with pulmonary arterial hypertension (PAH) susceptibility based on a case-control study with a total of 587 PAH patients and 736 healthy controls in southern Chinese. Results: We found that the rs619586A>G single nucleotide polymorphism (SNP) was significantly associated with PAH risk. The carriers with G variant genotypes had a decreased risk of PAH (odds ratio [OR]=0.69, 95% confidence interval [CI]=0.53–0.90, p=0.007) compared to the rs619586AA genotype. Further functional experiments indicated that the alteration from rs619586A to G in MALAT1 could directly upregulate X box-binding protein 1 ( XBP1 ) expression via functioning as the competing endogenous RNA (ceRNA) for miR-214, and consequentially inhibiting the vascular endothelial cells proliferation and migration in vitro by shortening S-M phase transition. Conclusions: Taken together, our findings propose that functional polymorphism rs619586A>G in MALAT1 gene plays an important role in PAH pathogenesis and may serve as a potential indicator for PAH susceptibility.

Background: Pneumatic tube systems (PTS) are widely used in many hospitals. Using PTS reduces turnaround time (TAT) and can improve patients’ outcome. Methods: We investigated whether clinically significant differences could be observed in CSF samples transported by pneumatic tube in comparison with samples transported by hand. Two aliquots from one sample were sent by PTS and by hand from the department of neurology or neurosurgery and compared. Results: Routine cytological and biochemical assessment was compared in 27 cases. There were no statistically significant changes (transport by hand vs. PTS) in glucose levels [data are expressed as median (minimum–maximum)] at 3.7 (2.5–8.6) mmol/L vs. 3.6 (2.7–8.6) mmol/L, p=0.96 or lactate levels at 1.8 mmol/L (1.1–5.5) vs. 1.8 mmol/L (1.1–5.4). We observed a statistically significant decline in total protein levels in samples transported by PTS at 0.56 g/L (0.19–4.29) vs. 0.49 g/L (0.18–4.3), p=0.008. We observed no changes in erythrocyte count at 5/μL (0–40,000) vs. 5/μL (0–40,106), mononuclear cells at 2/μL (1–145) vs. 3/μL (1–152), or polynuclear cells at 0/μL (0–235) vs. 0/μL (0–352). Spectrophotometric examination was performed in 20 cases. There were no statistically significant differences (transport by hand vs. transport by PTS) in NOA at 0.002 (0.001–1.537) vs. 0.001 (0.001–1.528), p=0.95 or NBA at 0.001 (0.001–0.231) vs. 0.001 (0.001–0.276), p=0.675. Samples transported by PTS were delivered faster than samples transported by courier (transport by hand vs. PTS) at 25 min (10–153) vs. 15 min (4–110), p=0.002. Conclusions: We found no significant changes in glucose, lactate levels and in any of the cytological parameters assessed, nor were statistically significant changes observed in the spectrophotometric parameters. We found a statistically significant decrease in total protein levels in samples transported by PTS. Transport by PTS can be faster than transport by hand.

Background: Quantitative assays using dried filter paper bloodspots (DBS) may be adversely affected by hematocrit (HCT) as an unknown variable. Studies have demonstrated the utility of the measurement of potassium (K) from DBS punches to estimate HCT. Because there is significant accrual of RBCs at the DBS perimeter, we investigated whether K measurement from ring-shaped specimens inclusive of the perimeter might provide an advantage over conventional interior circular sub-punch samples to estimate HCT. Methods: Primary samples were Li-heparin whole blood, with HCT as measured on concurrently-drawn K-EDTA specimens. DBS were formed by bolus addition of 40 μL whole blood to filter paper cards. Total bloodspot area was determined by image analysis. Removal of center sub-punch (P) samples of fixed area produced remainder ring (R) samples inclusive of the perimeter. Samples were extracted in K-EDTA (2.5 mmol/L) and measured for diluent-corrected K per area (α, μmol K/cm 2 ). Results: Forty-three patient samples were utilized. α was normally distributed: α(P)=1.23±0.26 μmol K/cm 2 ; α(R)=1.86±0.41 μmol K/cm 2 ; α(R)/α(P)=1.51±0.15. α was correlated with HCT: α(P)=0.030 HCT(%)+0.015 μmol K/cm 2 (r 2 =0.795); α(R)=0.052 HCT(%)+0.010 μmol K/cm 2 (r 2 = 0.912), but with higher resolution and lesser error for α(R). Conclusions: K per area (α) was significantly higher in R samples vs. P samples, with higher resolution for α(R) vs. HCT. Use of ring samples inclusive of the perimeter to estimate HCT for DBS via K measurement can provide an advantage over use of center sub-punch samples.

Background: Thyroid stimulating hormone (TSH) receptor autoantibodies (TRAb) are pathogenetic and diagnostic hallmarks of Graves’ disease (GD). Three varieties of TRAb have been described: stimulating (S-TRAb), blocking (B-TRAb), and apoptotic (A-TRAb) autoantibodies. Very recently, the first immunoassay method (Immulite TSI assay, Siemens Healthcare Diagnostics) declared to measure serum S-TRAb concentration, has been made available in an automated commercial platform. The aim of the study was to evaluate the ability of this new test to identify patients suffering from GD, in comparison with two current IMA methods for total TSH receptor autoantibodies (T-TRAb) measurement. Methods: Sera of 383 subjects [72 patients with untreated GD, 55 patients with autoimmune thyroiditis (AIT), 36 patients with multinodular non-toxic goiter, 100 patients with other non-thyroid autoimmune diseases (NTAD) and 120 healthy subjects (HS)] were evaluated. Results: The threshold obtained by receiver operating characteristic (ROC) analysis was 0.54 IU/L, very similar to that proposed by the manufacturer (0.55 IU/L). Thyroid-stimulating immunoglobulins (TSI) were positive in all GD patients and negative in all but three controls (clinical sensitivity and specificity of 100% and 98.7%, respectively). Passing and Bablok regression analysis and Bland-Altman plot showed an acceptable agreement between TSI Immulite assay and other two immunoassay methods (Cobas/Elecsys, Roche and TRAK RIA, BRAHMS Thermo Scientific). Conclusions: The diagnostic performance of fully automated Immulite TSI assay in GD patients is at least comparable to that of current TRAb immunoassays (IMAs) suggesting the possibility of including such assay in rapid and cost-saving diagnostic and monitoring algorithms. However, our results do not provide full evidence that this assay is specific for S-TRAb only, and future studies comparing Immulite TSI assay to stimulating activity are required.

Background: Global standardization of ferritin assays is lacking, which could have direct implications on the accurate measurement and comparability of ferritin concentration and iron deficiency (ID) prevalence rates in at-risk populations. Methods: We measured serum ferritin concentrations using four immunoassays: the s-ELISA and the AxSYM™ analyzer were compared among 420 non-pregnant Cambodian women; the Centaur ® XP analyzer, s-ELISA, and AxSYM™ analyzer were compared among a subset of 100 Cambodian women; and the s-ELISA and the Elecsys ® 2010 analyzer were compared among 226 Congolese children aged 6–59 months. Results: Median ferritin concentrations (adjusted for inflammation) ranged between 48 and 91 μg/L among Cambodian women and between 54 and 55 μg/L among Congolese children. ID prevalence ranged from 2% to 10% among Cambodian women and 5% to 7% among Congolese children. Bias between methods varied widely (–9 to 45 μg/L) among women, and was 43 μg/L among children. Bias was lower when ferritin values outside of the s-ELISA measurement range (>250 μg/L) were excluded. Conclusions: The observed differences in ferritin concentrations likely reflect different ferritin isoforms, antibodies, and calibrators used across assays and by different laboratories. However, despite differences in ferritin concentrations, ID prevalence was relatively similar and low across all methods.

Background: Dipeptidyl peptidase IV (DPPIV/CD26) plays an important role in T cell activation and immune regulation, however the role of this enzyme in early rheumatoid arthritis (eRA) has not been clearly defined. The aim of this study was to determine the serum activity of DPPIV, its expression on peripheral blood mononuclear cells (PBMC) and to examine possible correlations with disease activity (DAS28) in untreated patients with eRA. Methods: The study included 50 patients newly diagnosed with RA, who had not received any corticosteroid or disease modifying antirheumatic drugs (DMARD) therapy and whose conventional radiographs of hands and feet showed no structural damage. The control group consisted of 40 healthy volunteers. Also, 30 patients with chronic RA (cRA) were examined. The serum activity of DPPIV was determined by the direct photometric method, while expression of CD26 on PBMC was determined using flow cytometry. Results: Decreased DPPIV serum activity was detected in patients with eRA and cRA compared to the control group (p=0.024, p<0.0001, respectively). Although, the percentage of overall CD26+ white blood cells (WBC) was significantly decreased in eRA patients (p<0.001), the percentage of CD26+ lymphocytes and monocytes and mean fluorescence intensity of CD26 on these cells in eRA patients showed no significant difference compared to healthy volunteers. DAS28 showed no significant correlation with CD26 expression or DPPIV serum activity, but a significant inverse correlation between the duration of symptoms and DPPIV serum activity was observed. Conclusions: Our results show that a decrease in DPPIV serum activity, but not CD26 expression, is present in an early stage of rheumatoid arthritis.

Background: In the hematology department, the availability of biomarkers for early detection of infection is difficult to obtain. The present study aimed to compare the diagnostic values of neutrophil CD64 Index, procalcitonin (PCT), interleukin-6 (IL-6) and C-reactive protein (CRP) and to determine whether the combined analysis of these biomarkers offer stronger predictive power in the diagnosis for the infection of febrile patients. Methods: Neutrophil CD64 Index, PCT, IL-6 and CRP levels were determined in 356 febrile patients in the hematology ward from May 2013 to May 2015. Sensitivity, specificity, positive and negative likelihood ratios, positive and negative predictive values, receiver operating characteristic (ROC) areas under the curve (AUC), and logistic regression analysis were determined to evaluate the diagnostic values of these biomarkers. Results: The levels of the four biomarkers were higher in the infection patients (p<0.001), and the PCT and IL-6 were higher in the patients with positive microbial blood culture (p<0.01). The neutrophil CD64 Index, PCT, IL-6, CRP had AUCs of 0.95, 0.83, 0.75 and 0.73, respectively. The best cut-off value of the neutrophil CD64 Index to detect infections was 5.06, with high specificity (87.5%) and sensitivity (88.4%). Furthermore, neutrophil CD64 Index, PCT and IL-6 offered the best combination of diagnosis with sensitivity of 93.9% and an AUC of 0.95. In addition, the neutrophil CD64 Index may have a special value to assist the physician to diagnose infection in the neutropenic patients with fever. Conclusions: The neutrophil CD64 Index is useful for early identification of infections in febrile patients in the hematology department. The combined analysis of the CD64 Index, PCT and IL-6 could further improve its sensitivity.

Background: Lupus anticoagulant (LAC) detection represents diagnostic challenges among which the multitude of available reagents and interference by anticoagulant treatment. One of the two advised tests is the dilute Russell’s viper venom time (dRVVT). However, it is currently not clear whether all dRVVT reagents may be considered equivalent. The objective of the study was to evaluate the diagnostic performance of two dRVVT reagents, with special attention to the influence of anticoagulant therapy. Methods: STA ® -Staclot ® dRVV Screen/Confirm (Stago, Asnières-sur-Seine, France) and dRVT-LS/dRVTL-LR (Haematex, Hornsby, Australia) were evaluated on 443 patient samples [358 consecutive patients with LAC request including six antiphospholipid syndrome (APS) patients, 18 non-consecutively selected APS patients and 37 vitamin K antagonists (VKA)-treated and 30 direct oral anticoagulants (DOAC)-treated non-APS patients]. Additionally, pooled normal plasma (PNP) was spiked with factor deficient plasma (n=33) and DOAC calibrators (n=21) to evaluate sensitivity for factor deficiencies and false-positivity rates, respectively. Results: A higher number of samples were defined as LAC positive by Stago vs. Haematex [11.5% (41/358) vs. 3.63% (13/358)]. Most discordances were in the VKA and DOAC group. Haematex was less prone to VKA-related factor deficiencies, explaining the absence of false-positive LAC results in VKA-treated non-APS patients compared to 10.8% with Stago. We observed no false-positive LAC ratios with Haematex in DOAC-spiked PNP and a lower number in DOAC-treated non-APS patients. However, increased specificity seemed to be at cost of a reduced sensitivity as Haematex showed less positive APS patient samples (45.8% vs. 87.5%). Conclusions: dRVVT reagents differ in LAC sensitivity and for VKA and DOAC interference.

Background: Interpretation of alkaline phosphatase activity in children is challenging due to extensive changes with growth and puberty leading to distinct sex- and age-specific dynamics. Continuous percentile charts from birth to adulthood allow accurate consideration of these dynamics and seem reasonable for an analyte as closely linked to growth as alkaline phosphatase. However, the ethical and practical challenges unique to pediatric reference intervals have restricted the creation of such percentile charts, resulting in limitations when clinical decisions are based on alkaline phosphatase activity. Methods: We applied an indirect method to generate percentile charts for alkaline phosphatase activity using clinical laboratory data collected during the clinical care of patients. A total of 361,405 samples from 124,440 patients from six German tertiary care centers and one German laboratory service provider measured between January 2004 and June 2015 were analyzed. Measurement of alkaline phosphatase activity was performed on Roche Cobas analyzers using the IFCC’s photometric method. Results: We created percentile charts for alkaline phosphatase activity in girls and boys from birth to 18 years which can be used as reference intervals. Additionally, data tables of age- and sex-specific percentile values allow the incorporation of these results into laboratory information systems. Conclusions: The percentile charts provided enable the appropriate differential diagnosis of changes in alkaline phosphatase activity due to disease and changes due to physiological development. After local validation, integration of the provided percentile charts into result reporting facilitates precise assessment of alkaline phosphatase dynamics in pediatrics.

Background: Apoptosis plays a critical role in cancer cell survival and tumor development. We provide a hypothesis-generating screen for further research by exploring the expression profile and genetic variability of caspases (2, 3, 7, 8, 9, and 10) in breast carcinoma patients. This study addressed isoform-specific caspase transcript expression and genetic variability in regulatory sequences of caspases 2 and 9. Methods: Gene expression profiling was performed by quantitative real-time PCR in tumor and paired non-malignant tissues of two independent groups of patients. Genetic variability was determined by high resolution melting, allelic discrimination, and sequencing analysis in tumor and peripheral blood lymphocyte DNA of the patients. Results: CASP3 A+B and S isoforms were over-expressed in tumors of both patient groups. The CASP9 transcript was down-regulated in tumors of both groups of patients and significantly associated with expression of hormonal receptors and with the presence of rs4645978-rs2020903-rs4646034 haplotype in the CASP9 gene. Patients with a low intratumoral CASP9A/B isoform expression ratio (predicted to shift equilibrium towards anti-apoptotic isoform) subsequently treated with adjuvant chemotherapy had a significantly shorter disease-free survival than those with the high ratio (p=0.04). Inheritance of CC genotype of rs2020903 in CASP9 was associated with progesterone receptor expression in tumors (p=0.003). Conclusions: Genetic variability in CASP9 and expression of its splicing variants present targets for further study.

Background: Epithelial-mesenchymal transition (EMT) is a critical process which involves in tumor metastasis. As an important EMT marker gene, CDH1 (E-cadherin) expression and its clinical implication in acute myeloid leukemia (AML) remain largely elusive. Methods: Real-time quantitative PCR (RQ-PCR) was carried out to examine CDH1 transcript level in 123 de novo AML patients and 34 controls. Results: Compared with controls, CDH1 was significantly downregulated in AML (p<0.001). The median level of CDH1 expression divided total AML patients into CDH1 low-expressed ( CDH1 1ow ) and CDH1 high-expressed ( CDH1 high ) groups. There were no significant differences between the two groups in age, peripheral blood cell counts, complete remission (CR) rate, and the distribution of FAB/WHO subtypes as well as karyotypes/karyotypic classifications (p>0.05). However, CDH1 1ow group tended to have a higher bone marrow (BM) blasts (p=0.093). The spearman correlation analysis further illustrated a trend towards a negative correlation between CDH1 expression level and BM blasts (r=–0.214, p=0.052). CDH1 low group had a tendency towards a lower frequency of N/K-RAS mutations (p=0.094). Furthermore, CDH1 low patients had markedly shorter overall survival (OS) time in cytogenetic normal AML (CN-AML) (p=0.019). Both univariate and multivariate analyses confirmed the prognostic value of CDH1 expression in CN-AML patients (p=0.027 and 0.033, respectively). Conclusions: CDH1 downregulation acted as an independent prognostic biomarker in CN-AML patients.

Background: Contrast induced nephropathy (CIN) has been proven to be a clinical condition related to adverse cardiovascular outcomes. In recent studies, the monocyte to high density lipoprotein ratio (MHR) has been postulated as a novel parameter associated with adverse renal and cardiovascular outcomes. In this study we investigated the association of MHR with CIN in ST-segment elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PCI). Methods: Consecutive STEMI patients treated with primary PCI were prospectively recruited. Subjects were categorized into two groups; as patients who developed CIN (CIN+) and patients who did not develop CIN (CIN–) during hospitalization. CIN was defined as either a 25% increase in serum creatinine from baseline or 44.20 µmol/L increase in absolute value, within 72 h of intravenous contrast administration. Results: A total number of 209 patients were included in the study. Thirty-two patients developed CIN (15.3%). In the CIN (+) patients, monocytes were higher [1.02 (0.83–1.39) vs. 0.69 (0.53–0.90) 10 9 /L, p<0.01] and HDL cholesterol levels were lower [0.88 (0.78–1.01) vs. 0.98 (0.88–1.14) mmol/L, p<0.01]. In addition, MHR was significantly higher in the CIN (+) group [1.16 (0.89–2.16) vs. 0.72 (0.53–0.95) 10 9 /mmol, p<0.01]. In multivariate logistic regression analysis, MHR, Mehran score, AGEF score and CV/eGFR were independently correlated with CIN. Conclusions: Higher MHR levels may predict CIN development after primary PCI in STEMI patients.

Background: In individuals with atherosclerotic risk factors, endothelial dysfunction (ED) appears as an early phase in the development of clinical symptoms. Recent studies indicate that adropin, a newly identified peptide, participates in cardiovascular health through the regulation of several metabolic events including angiogenesis and blood flow. In this study, we aimed to determine the relation of adropin with biochemical and radiologic parameters which reflect ED such as endothelial nitric oxide synthase (eNOS), endothelin 1 (ET-1), nitric oxide (NO) and flow-mediated dilatation (FMD) along with the routine biochemical measurements in patients recently diagnosed with metabolic syndrome (MetS). Methods: Fasting blood samples from 110 patients with MetS diagnosed according to the NCEP ATP III-2005 criteria were collected to measure the concentrations of adropin and other parameters including the lipid profile, insulin and glucose. Serum NOx concentrations were determined by measuring NO 2 plus NO 3 . FMD test was performed by ultrasonography, and patients were stratified as FMD (+) or (–). Data were compared between these two subgroups and also with matching healthy controls (n=50). Biochemical data were evaluated using Student’s t or Mann-Whitney U tests. Results: Fifty-nine subjects had ED (+) and the remaining 101 subjects were ED (–). In the first group, adropin levels were significantly lower than the latter (2.13±1.05 vs. 3.41±1.63 ng/mL, respectively; p<0.001) and independently associated with FMD positivity as assessed by the logistic regression analysis. Conclusions: Low adropin level in circulation is related to ED and has a close association with FMD. Any alterations in its level may be of help in order to assess the development of ED before the occurrence of clinical symptoms in patients with metabolic syndrome.

Background: Potassium disorders have been linked to adverse outcomes in various medical conditions. However, the association of preoperative serum potassium with postoperative outcome is not well established. We aimed to examine the association between preoperative potassium with a 30-day mortality and adverse cardiovascular event (MACE). Methods: We conducted a cohort study using a prospectively collected database of patients, undergoing surgical procedures from 1998 to 2013 in the VA Western New York Healthcare System, which are reported to the Veterans Affairs Surgical Quality Improvement Program (VASQIP). The patients were categorized into three groups based on their documented preoperative potassium concentrations. Hypokalemia was defined as serum potassium concentration <4 mmol/L and hyperkalemia was defined as serum potassium concentrations >5.5 mmol/L. The values within the range of 4.0–5.5 mmol/L were considered as normokalemia and used as the control group. Statistical analyses included Chi-square test, analysis of variance and multivariate logistic regression to estimate the risk of MACE within 30 days of surgery. Results: Study included 5959 veterans who underwent surgery between 1998 and 2013. The patients in the hyperkalemics group had lower kidney function compared to the other two groups. The frequency of MACE was 13.6% in hypokalemics and 21.9% in hyperkalemics that were both significantly higher than 4.9% in controls. In multivariate logistic regression the hazard risk (HR) ratios of MACE were (2.17, 95% CI 1.75–2.70) for hypokalemics and (3.23, 95% CI 2.10–4.95) for hyperkalemics when compared to normokalemic controls. Conclusions: Preoperative hypokalemia and hyperkalemia are both independent predictors of MACE within 30 days.

Background: Fructosamine 3 kinase (FN3K) is a deglycating enzyme, which may play a key role in reducing diabetes-induced organ damage by removing bound glucose from glycated proteins. We wanted to develop a simple colorimetric method for assaying FN3K activity in human body fluids. Methods: Glycated bovine serum albumin (BSA) was obtained by glycation with a 10% glucose solution at 37 °C. After 72 h, glycated BSA was dialyzed against phosphate buffered saline (0.1 mol/L, pH 7.4). The dialyzed solution (containing ±1000 µmol/L fructosamine) was used as an FN3K substrate. In the assay, 300 µL of substrate was incubated with 50 µL of serum and 100 µL of MgCl 2 (0.7 mmol/L)/ATP (3.2 mmol/L). The fructosamine concentration was determined at the start and after incubation (120 min, 25 °C). The decrease in fructosamine concentration over time is a measure for the FN3K activity (1 U corresponding to 1 µmol/min). Concomitantly, the FN3K SNP rs1056534 and the ferroportin SNP rs1156350 were genotyped. Results: Within-assay CV was 6.0%. Reference values for FN3K activity in serum were 14.2±1.6 U/L (n=143). Reference values for FN3K were neither age- nor sex-dependent. The various FN3K SNP rs1056534 genotypes showed no significant differences in serum FN3K activity. In diabetics (n=191), values (14.0±2.2 U/L) were comparable to those of the controls. FN3K activity in erythrocytes was significantly higher (170.3±7.6 U/L). The intra-erythrocytic FN3K activity makes the results prone to hemolysis. FN3K activity depended on the ferroportin Q248H genotypes, with the highest value for the wild type genotype. Neither transferrin saturation nor ferritin were confounders for the FN3K activity. FN3K activity was significantly (p<0.0001) correlated with HbA 1c values, although the correlation between FN3K and HbA 1c was weak. Conclusions: The simple colorimetric method allows determining FN3K activity in human serum. The assay may be useful for studying the impact of deglycation processes in diabetes mellitus.