Band 43, Heft 5

A number of improvement proposals and corrections of the German Rili-BAEK (Guideline of the German Medical Association on Quality Assurance in Medical Laboratory Examinations) are discussed with special focus on the internal and external quality assurance (IQA/EQA) as well as reference intervals for quantitative results. Particular attention is paid to reconsider the retrospective analysis of control measurements. Such an analysis can be very useful to monitor establishing errors of measurement even before they become critical. The present method “Quadratischer Mittelwert der Messabweichung (QMMA)” has proved to be ineffective. Furthermore, the current idea of a common limit for single control measures and the retrospective statistics must be revised. As a more sophisticated concept, the novel Adaptive Retrospective Monitoring (ARM) has been developed. ARM is recommended as the new minimum requirement for the entire internal quality assurance. Further proposals to enhance clarity are given concerning the release decisions of medical devices and the EQA. Individualized medicine begins with a patient-specific interpretation of analytic results. This requires standardized subgroup-specific reference intervals with smooth age-related adaptations. Only large laboratories are able to ensure the desired specificity and a sufficient statistical significance of self-developed in-laboratory reference intervals. Hence, the need of a central database for harmonized reference intervals is discussed and recommended. Suitable and consistent reference intervals are also an essential prerequisite for unitless laboratory values like the zlog value.

Background A pilot external quality assurance (EQA) survey for the free light chain (FLC) assay was developed and implemented in Korea. Methods Survey data over 6 years (2010–2015) were collected retrospectively and Sigma metrics were calculated for method-specific peer groups. Results Nineteen to 29 laboratories participated in the EQA survey, and nephelometric (20%) and turbidimetric (80%) methods were used. Using a previously published clinically relevant reference change value (RCV) of 54.5% as the tolerance limit, the method-specific median Sigma metrics of kappa (κ) and lambda (λ) FLC achieved greater than Three-Sigma for 86–97% of all EQA distributions, and Five-Sigma for 48–72% of all distributions. Conclusions This EQA analysis of FLC assay applied clinically relevant quality specifications using Sigma metrics. During the 6-year EQA survey, we found that most of the results from participating laboratories meet clinically relevant quality specifications. In addition, method-specific differences were noted for λ FLC, at FLC concentrations above the initial measuring range that require a sample dilution.

Background Vitamin D plays a key role in calcium homeostasis and contributes to the regulation of the immune system. Furthermore, vitamin D deficiency has been reported to be associated with autoimmune diseases (AIDs), especially with multiorgan AIDs. Various multiorgan AIDs may be different based on the vitamin D status. This study aims to investigate the serum 25-hydroxyvitamin D (25(OH)D) levels in patients with different common multiorgan AIDs. Methods A total of 295 patients with multiorgan AIDs treated in our hospital from January 2012 to September 2018 were recruited, including 137 cases of rheumatoid arthritis (RA), 85 cases of systemic lupus erythematosus (SLE), 32 cases of Sjögren’s syndrome (SS) and 41 cases of mixed connective tissue disease (MCTD); 47 apparently healthy individuals were also recruited as controls. The serum 25(OH)D levels in patients with different multiorgan AIDs were measured with Roche electrochemiluminescence immunoassay and statistically analyzed the proportion of patients with normal, insufficiency and deficiency in 25(OH)D levels in different multiorgan diseases. The 25(OH)D levels of different multiorgan AID groups and healthy controls were also compared. Results Incidences of 25(OH)D deficiency in the RA, SLE, SS and MCTD groups were 21.2%, 35.3%, 25.0% and 22.0%, respectively, with significant inter-group differences (p < 0.05). The incidence in the SLE group was higher than in the RA, SS and MCTD groups, indicating severe 25(OH)D deficiency in patients with SLE. Significant inter-group differences (p < 0.05) were detected in the serum 25(OH)D levels in different multiorgan AID groups and in the healthy control group. Further pairwise comparison found a significantly higher level of 25(OH)D in the healthy control group than in the SLE, SS, RA and MCTD groups (p < 0.05). Moreover, the 25(OH)D status in the SLE group was significantly lower than that in the SLE, SS, RA and MCTD groups (p < 0.05). Conclusions Serum 25(OH)D deficiency and a low 25(OH)D status are commonly seen in patients with different multiorgan AIDs compared to healthy controls, warranting vitamin D supplementation. Severe 25(OH)D deficiency and a lower 25(OH)D status were found in patients with SLE.

Background The dual cascade algorithm which involves screening and confirmation of antinuclear antibodies (ANAs) by further reflex testing is widely used in the detection of ANAs. We aimed to investigate this algorithm which is commonly used in many laboratories. Methods A total of 475 sera obtained from patients with a clinical suspicion of systemic autoimmune rheumatic diseases (SARDs) upon which three expert assessors agreed for interpretation in the indirect immunofluorescence (IIF) test were determined and tested by the line immunoassay (LIA) containing 16 antigens. The results of the tests were statistically compared and evaluated. Results In 141 of the sera (29.7%), there was an agreement between ANA-IIF(+) and LIA(+) results. The overall agreement rate between the two tests for positivity and negativity only was 85.5% with a Cohen’s κ coefficient of 0.69. In 118 of these 141 sera (83.7%), pattern and associated ANA agreement was detected with an overall agreement rate of 80.6% and a Cohen’s κ coefficient of 0.57. The highest agreement between the pattern and associated ANAs was seen in centromere, dense fine speckled (DFS) and cytoplasmic reticular patterns. In these patterns, the rate of anti-centromere-associated protein B (CENP-B), anti-DFS and anti-antimitochondrial antibody M2 (anti-AMA-M2) antibodies were 93.4%, 92.3% and 66.7%, respectively. Conclusions We found an overall moderate agreement between IIF screening and LIA confirmation tests. However, the level of agreement varies according to the pattern type. The discrepancy in agreement rates may cause false reflex test requests. Our results highlight the need for collaboration between clinical and laboratory professionals in selected cases instead of the reflex testing approach.

Background Ischemia-modified albumin (IMA) is an isotype of albumin that increases under oxidative stress, and plasma thiols are main defense mechanisms against oxidative stress. The objective of this study was to investigate thiol-disulfide homeostasis and serum IMA levels in postherpetic neuralgia (PHN) patients. Methods A total of 29 PHN patients and 30 healthy controls were included in the study. Serum total and native thiol concentrations and serum disulfide concentration were measured using the method described by Erel and Neselioglu. The albumin cobalt binding test was used to measure serum IMA levels. Results Serum IMA levels were 1.21 ± 0.58 AU and 0.75 ± 0.09 AU in the PHN and control groups, respectively (p < 0.001). Serum total thiol concentrations were found to be 421.62 ± 90.28 μmol/L and 598.36 ± 73.63 μmol/L in the PHN and control groups, respectively (p < 0.001). Serum native thiol concentrations were found to be 365.75 ± 92.07 μmol/L and 531.90 ± 72.9 μmol/L in the PHN and control groups, respectively (p < 0.001). Serum disulfide concentrations were found to be 33.23 ± 5.33 μmol/L and 27.93 ± 7.81 μmol/L in the PHN and control groups, respectively (p = 0.003). The native thiol/total thiol ratio was significantly lower, and the disulfide/total thiol and disulfide/native thiol ratios were significantly higher in the PHN group compared to the controls. Conclusions IMA levels are high and dynamic thiol/disulfide homeostasis is disrupted in PHN patients.

Background The potential effect of increase in hemoglobin (Hb) A 2 and HbF on glycated hemoglobin (HbA 1c ) measurements were investigated using a high-performance liquid chromatography (HPLC) method compared with an immunoturbimetric assay. Methods Samples producing abnormal chromatograms during the measurement of routine HbA 1c testing with HPLC were further analyzed to characterize abnormal Hb variants. Patients were divided into three groups that had only high HbF (group 1), only high HbA 2 (group 2), and both high HbA 2 and HbF (group 3). HbA 1c values of patients were re-assayed using the immunoturbidimetric method (Advia, Siemens Healthcare, Germany). Results HbA 1c levels were significantly higher in all groups measured by immunoassay than in HPLC. We found a positive correlation between HPLC and immunoturbidimetry in the group 2 and a slight correlation in the group 1. There was no correlation between the two methods in group 3. Conclusions HbA 1c measurement by HPLC method interfering with elevated HbA 2 and HbF, especially HbF, should be verified by an immunoturbidimetric method.

Background The most important antioxidant for erythrocytes is glutathione. In this study, a non-enzymatic recycling spectrophotometric method was developed to measure oxidized and reduced glutathione (GSH) levels in erythrocytes. The newly developed method consists of two steps. In the first step, the levels of GSH were determined in the sample. Subsequently, total glutathione levels were measured by reducing the oxidized glutathione (GSSG) with sodium borohydride (NaBH 4 ). Half of the difference between total glutathione and GSH gives the GSSG. Results The new method was linear between 0 and 3000 μmol/L (r 2  = 0.999). The percentage recovery measured by the developed method was 100.2 ± 2.4%. The total precision of the total glutathione, GSH and GSSG was 1.26%, 1.02% and 6.65%, respectively. GSH levels were significantly lower in patients with type 2 diabetes mellitus (DM), while GSSG levels were significantly higher (p < 0.05). Hemoglobin A 1c (HbA 1c ) levels were negatively correlated with GSH levels, whereas positively correlated with GSSG (p < 0.05). Conclusions In conclusion, this method is easy to apply in routine practice with high accuracy, precision and reproducibility.

Efficacy estimation of medical interventions in clinical trials requires diagnostics to assess the study endpoint. The imperfect nature of diagnostics often leads to biased efficacy estimations, usually underestimation, that could result in failure of clinical trials. Adjustment methods can be used if sensitivity and specificity are known, but they are not regularly applied. Double-arm clinical trials are the standard for demonstrating the superiority of a medical intervention. However, sometimes single-arm trials are the only option: for example, if a parallel group trial design with a control group is regarded as unethical. Based on the Gart and Buck prevalence estimator (aka the Rogan-Gladen estimator), we demonstrate how the concept of diagnostic accuracy-adjusted effect estimation can be used for estimating the efficacy in single-arm trials. The accuracy of the diagnostic measure (sensitivity and specificity) used for endpoint assessment as well as the predictive accuracy of a predictor and its allocation among the study population have to be known to obtain consistent efficacy estimation of a medical intervention. If double-arm trials are not feasible, an approach such as that described here can provide evidence regarding the efficacy of a medical intervention based on a single-arm trial.