Clinical chemistry and laboratory medicine最新文献

Objectives: The quantification of functional C1 inhibitor activity (fC1-INH) is an important tool to diagnose bradykinin-mediated angioedema (AE), whether hereditary or acquired. For that an accurate assay is necessary, therefore we evaluated the analytical performances of a fC1-INH chromogenic assay (Berichrom^®, Siemens) performed utilizing an Optilite turbidimeter (Binding Site).

Methods: fC1-INH was quantified by means of the chromogenic assay Berichrom^®. Internal quality controls were used to determine the precision of the assay. Stability under various storage and matrix conditions, uncertainty, linearity, interference (of hemolysis, lipemia, and icterus), agreement with the manual Technochrom^® assay, and diagnostic performances were further evaluated on samples from patients and healthy donors.

Results: The fC1-INH Berichrom^® assay presented good performances regarding intra- and inter-assay precision (CV: 1.3-4.5 % and 3.0-6.0 %, respectively), expanded uncertainty (5.5 % at normal level and 12.5 % at the clinical threshold) and linearity (rho²>0.99: range 7-130 % activity). Addition of interfering substances (hemoglobin <16 g/L, intralipid^® <12 g/L, and bilirubin <1 g/L) did not affect fC1-INH quantification. fC1-INH activity from healthy donors remained stable in citrate whole blood until 4 days at room temperature, and 7 days when plasma was collected. Agreement between the automated Berichrom^® assay and the manual Technochrom^® assay (n=47) was excellent as obtained with both quantitative (Deming regression and Bland-Altman difference plot) and qualitative (Kappa index=1) analyses. Finally, the diagnostic performance of the quantification of fC1-INH for AE evaluated on 81 patients revealed a sensitivity of 100 %, a specificity of 97.2 %, a positive predictive value of 83.3 % and a negative predictive value of 100 %.

Conclusions: The automated fC1-INH Berichrom^® assay showed good performance, both at the analytical and diagnostic/clinical levels that allowed its usage in a clinical laboratory for C1-INH-dependent bradykinin-mediated AE research in combination with quantitative C1-INH and C4 determinations.

Objectives: Internal and external quality assurance materials often use highly processed matrixes. This can render the materials non-commutable. Monitoring laboratory methods with patient medians helps in identifying and correcting systematic errors that may affect diagnostic accuracy. The aim of the present study was to use HbA_1c patient results for monitoring of method performance over time.

Methods: Test HbA_1c results from 2010 to 2022 was analyzed (n=722,553) regarding changes over time and seasonal variation. The HbA_1c testing was initially performed on a Cobas 501 instrument using immunological detection but in May 2017 the method was replaced by capillary electrophoresis on Capillarys 3 Tera.

Results: There was a steady decrease in HbA_1c values. From 2011 to 2021 the decrease was for 0.10 percentile 6.6 %, lower quartile 7.9 %, median 10.2 %, mean values 9 %, upper quartile 11.2 %, and 0.90 percentile 9.3 %. No clear shift in HbA_1c levels was observed due to the shift in methods. The median HbA_1c values per month was approximately 44 mmol/mol (6.2 %, DCCT/NGSP). The only month with a median HbA_1c that differed by more than 1 mmol/mol was July with a median value of 42 mmol/mol (6.0 %).

Conclusions: The patient data showed a similar decrease as in the National Diabetes Register which indicates that the method is stable over time without any sudden changes and that the seasonal variation is low. The continuous decrease in HbA_1c values over time is most likely to a shift towards earlier detection of patient with diabetes and improved treatment.

Objectives: Conventional autoverification rules evaluate analytes independently, potentially missing unusual patterns of results indicative of errors such as serum contamination by collection tube additives. This study assessed whether multivariate anomaly detection algorithms could enhance the detection of such errors.

Methods: Multivariate Gaussian, k-nearest neighbours (KNN) distance, and one-class support vector machine (SVM) anomaly detection models, along with conventional limit checks, were developed using a training dataset of 127,451 electrolyte, urea, and creatinine (EUC) results, with a 5 % flagging rate targeted for all approaches. The models were compared with limit checks for their ability to detect atypical EUC results from samples spiked with additives from collection tubes: EDTA, fluoride, sodium citrate, or acid citrate dextrose (n=200 per contaminant). The study additionally assessed the ability of the models to identify 127,449 single-analyte errors, a potential weakness of multivariate models.

Results: The KNN distance and SVM models outperformed limit checks for detecting all contaminants (p-values <0.05). The multivariate Gaussian model did not surpass limit checks for detecting EDTA contamination but was superior for detecting the other additives. All models surpassed limit checks for identifying single-analyte errors, with the KNN distance model demonstrating the highest overall sensitivity.

Conclusions: Multivariate anomaly detection models, particularly the KNN distance model, were superior to the conventional approach for detecting serum contamination and single-analyte errors. Developing multivariate approaches to autoverification is warranted to optimise error detection and improve patient safety.

While Six Sigma is used in different disciplines to improve quality, Tony Badric and Elvar Theodorsson in a recent paper in CCLM have questioned Six Sigma application in medical laboratory concluding Six Sigma has provided no value to medical laboratory. In addition, the authors have expanded their criticism to Total Analytical Error (TAE) model and statistical quality control. To address their arguments, we have explained the basics of TAE model and Six Sigma and have shown the value of Six Sigma to medical laboratory.

Objectives: Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by homozygous deletion and compound heterozygous mutations in survival motor neuron 1 (SMN1), with severity tied to the copy number of survival motor neuron 2 (SMN2). This study aimed to develop a rapid and comprehensive method for the diagnosis of SMA.

Methods: A total of 292 children with clinically suspected SMA and 394 family members were detected by the amplification refractory mutation system polymerase chain reaction-capillary electrophoresis (ARMS-PCR-CE) method, which targeted 19 reported mutations, and the results were compared with those in multiplex ligation-dependent probe amplification (MLPA). Individuals with identified point mutations were further confirmed by SMN1 long-range PCR and Sanger sequencing.

Results: A total of 202 children with SMA, 272 carriers, and 212 normal individuals were identified in this study. No difference was found in the R-value distribution of exons 7 and 8 in SMN1 and SMN2 among these cohorts, with coefficients of variation consistently below 0.08. To detect exon 7 and 8 copy numbers in SMN1 and SMN2, the ARMS-PCR-CE results were concordant with those of MLPA. Approximately 4.95 % (10/202) of the study patients had compound heterozygous mutations.

Conclusions: The ARMS-PCR-CE assay is a comprehensive, rapid, and accurate diagnostic method for SMA that simultaneously detects copy numbers of exons 7 and 8 in SMN1/SMN2, as well as 19 point mutations in SMN1 and 2 enhancers in SMN2. This approach can effectively reduce the time frame for diagnosis, facilitating early intervention and preventing birth defects.

Objectives: Autoimmune nodopathy (AN) is a life-threatening peripheral neuropathy mediated by four autoantibodies targeting axoglial cell adhesion molecules at the nodes of Ranvier: Neurofascin-155 (Nfasc155), PanNeurofascin (PanNfasc), Contactin-1 (CNTN1), and Contactin-associated protein 1 (CASPR1). Antibody detection is a strong biomarker for AN diagnosis and treatment monitoring. The aim of this study was to develop an immuno-dot assay (immuno-DOT) compatible with routine implementation in medical laboratories.

Methods: This new approach was compared to standard techniques: indirect immunofluorescence assay, cell-based assay, and ELISA. Sensitivities (Se) and specificities (Sp) were calculated on a cohort composed of 58 patients diagnosed with AN, 50 seronegative patients with chronic inflammatory demyelinating polyradiculoneuropathy, 20 healthy controls, 30 patients with Guillain-Barré syndrome, 20 with monoclonal gammopathy and 20 with Charcot-Marie-Tooth disease. The patients were diagnosed with AN based on compatible electro-clinical arguments and at least two positive standard techniques.

Results: Immuno-DOT sensitivities and specificities were Se=91 %, Sp=97 % for anti-Nfasc155; Se=80 %, Sp=94 % for anti-PanNfasc; Se=93 %, Sp=98 % for anti-CNTN1; and Se=87 %, Sp=94 % for anti-CASPR1. Immuno-DOT allowed the diagnosis within 3 h and the accurate follow-up of the immune reactivity and isotype, and dot intensity correlated with antibody titers following treatments. A longitudinal study indicated that immuno-DOT yielded reliable results even after six months of storage at -20 °C.

Conclusions: The diagnostic performance of immuno-DOT was satisfactory and compatible with routine implementation in medical laboratories.