Clinical chemistry and laboratory medicine最新文献

Objectives: C-peptide is an equimolar by-product of insulin biosynthesis. It is used clinically to assess insulin secretion and differentiate types of diabetes. However, the lack of standardization across assays limits its broader application. This study aimed to examine discrepancies between the leading C-peptide measurement methods used in clinical laboratories and propose a solution to reduce them based on a complete traceability chain.

Methods: Two sets of serum samples were distributed to 10 manufacturers of C-peptide assays. The first set (A, n=20) was analyzed independently by each manufacturer, who then returned their results to us. Subsequently, we sent out the second set (B, n=20) along with the reference values for set A. For set B, each manufacturer provided both non-calibrated and recalibrated values for each sample. The recalibration was performed according to each manufacturer's internal standard protocols. We assessed how recalibration affected agreement between methods and alignment with the reference method. Non-parametric statistical approaches, including Passing-Bablok regression, level of agreement, and standard deviation analysis, were applied to compare data from multiple perspectives.

Results: Despite most manufacturers using the same WHO C-peptide calibrator material, significant disagreement was observed between methods prior to recalibration. Recalibration with matrix-appropriate serum samples reduced the discordance among assays, bringing them closer to the reference method. Overall, recalibration reduced both systematic bias and individual assay disagreement.

Conclusions: These findings underscore the importance of appropriate calibration schemes to improve agreement across C-peptide assays, enhancing the accuracy of C-peptide testing for clinical practice.

Objectives: Careful consideration of the pre-analytical process for urine examination is essential to avoid errors and support accurate results and decision-making. Our objective was to assess the impact of various pre-analytical factors on urine test strip and quantitative chemistry results, including stability, tube type, fill volume, and centrifugation.

Methods: Residual random urine specimens were identified. Stability of 10 urine test strips and 13 quantitative chemistry parameters were assessed at eight time points (2, 4, 6, 8, 24, 48, 72, and 96 h) at room temperature (RT) and 2-8 °C (n=10-20 samples). The effect of additional pre-analytical variables was assessed, including using preservative tubes for urine chemistry as well as preservative tube underfilling and centrifugation on urine test strip results (n=10 samples).

Results: Seven of the ten urine tests strips evaluated met the minimal agreement criteria for stability (Cohen's kappa >0.70) across all conditions. A Cohen's kappa value of <0.70 was observed for pH (48 h), glucose (72 h), and protein (96 h) at RT. All 13 urine chemistry analytes remained stable at defined time points and conditions. Underfilling preservative tubes for urine test strips and centrifugation demonstrated no significant effect. The impact of using preservative tubes for urine chemistry was negligible with the exception of sodium and osmolality.

Conclusions: These findings highlight the pre-analytical factors that impact urine specimen evaluation and may be useful in informing clinical laboratory practices. Acceptable stability window for urine test strips should be considered in the context of the proportion of pathological samples evaluated.

Objectives: To compare a new ready-to-use monotest immunoassay, CHORUS Promonitor, for the quantification of serum biological drug levels and anti-drug antibodies of anti-TNF agents, against the reference batch-based ELISA test, Promonitor.

Methods: Blood samples were collected from patients treated with anti-TNF agents, infliximab (IFX) or adalimumab (ADL). IFX and ADL levels, as well as anti-IFX and anti-ADL antibodies were quantified and compared between the standard ELISA reference test, Promonitor, and the automated monotest ELISA assay, CHORUS Promonitor. Data analysis included both qualitative and quantitative comparison between both tests. For the qualitative comparison, overall percent agreement (OPA) was calculated. For the quantitative comparison, Passing-Bablok regression analysis and Bland-Altman analysis were used.

Results: For IFX and ADL levels, the qualitative overall agreement between methods was 100 % (Cohen's coefficient=1). For anti-IFX and anti-ADL antibodies, OPA was 98.8 % and 97.3 %, respectively. Quantitative comparison indicated a very strong correlation between both assays: IFX (r=0.97, n=74), ADL (r=0.95, n=54), anti-IFX (r=0.93, n=72), and anti-ADL (r=0.97, n=61). The regression analysis determined an excellent comparability of drug levels between methods. Bland-Altman analysis showed a bias difference between assays of 6 % for IFX, 0 % for ADL, 24 % for anti-IFX, and 14 % for anti-ADL.

Conclusions: Monotest CHORUS Promonitor was a reliable assay to quantify IFX, ADL, anti-IFX and anti-ADL in samples with comparable results to those obtained with the reference batch-based ELISA technique.

Objectives: External quality assessment (EQA) programs play a pivotal role in harmonizing laboratory practices, offering users a benchmark system to evaluate their own performance and identify areas requiring improvement. The objective of this study was to go through and analyze the UK NEQAS "Immunology, Immunochemistry and Allergy" EQA reports between 2012 and 2021 to assess the overall level of harmonization in autoimmune diagnostics and identify areas requiring improvement for future actions.

Methods: The EQA programs reviewed included anti-nuclear (ANA), anti-dsDNA, anti-centromere, anti-extractable nuclear antigen (ENA), anti-phospholipids, anti-neutrophil cytoplasm (ANCA), anti-proteinase 3 (PR3), anti-myeloperoxidase (MPO), anti-glomerular basement membrane (GBM), rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA), mitochondrial (AMA), liver-kidney-microsomal (LKM), smooth muscle (ASMA), APCA, and celiac disease antibodies.

Results: In the analyzed period, the number in participating laboratories showed an increase for almost all programs. Among solid phase methods, the use of ELISA techniques showed a progressive reduction, while new technologies, such as the fluoroenzymatic immunoassay, chemiluminescence immunoassay, Luminex and immunoblot showed an increased number of users. The number of results complying with the expected negative or positive target slightly increased for almost all antibodies in the last decade. A description of the most frequent causes of mistakes or misinterpretation for each specific test and method is also provided in this study.

Conclusions: Although numerous challenges need to be addressed in the area of autoantibody detection to enhance testing quality and attain higher harmonization, the period analyzed revealed that the ever-expanding range of autoantibodies, coupled with the introduction of new tests and methodologies and the advent of automated platforms, has brought about significant changes in autoimmune diagnostics.

Objectives: Urinary steroid profiling after hydrolysis of conjugates is an emerging tool to differentiate aggressive adrenocortical carcinomas (ACC) from benign adrenocortical adenomas (ACA). However, the shortcomings of deconjugation are the lack of standardized and fully validated hydrolysis protocols and the loss of information about the originally conjugated form of the steroids. This study aimed to evaluate the quality of the deconjugation process and investigate novel diagnostic biomarkers in urine without enzymatic hydrolysis.

Methods: 24 h urine samples from 40 patients with ACC and 40 patients with ACA were analyzed by untargeted metabolomics using liquid chromatography-high-resolution mass spectrometry both unmodified and after hydrolysis with arylsulfatase/glucuronidase from Helix pomatia. Both approaches were compared regarding the differentiation of ACC vs. ACA via ROC analyses and to evaluate the hydrolyzation efficiency of steroid conjugates.

Results: Steroid glucuronides were fully deconjugated, while some disulfates and all monosulfates were still largely detectable after enzymatic hydrolysis, suggesting incomplete and variable deconjugation. In unhydrolyzed urine, steroid monosulfates showed the best differentiation between ACC and ACA (highest AUC=0.983 for C₂₁H₃₂O₆S, followed by its isomer and two isomers with the molecular formula C₂₁H₃₂O₇S). Moreover, several disulfates were highly abundant and increased in ACC compared to ACA.

Conclusions: This work highlights the limitations of hydrolyzing steroid conjugates before analysis and shows a possible superiority of a direct analysis approach compared to a hydrolysis approach from a methodological point of view and regarding diagnostic accuracy. Several steroid conjugates were found as promising diagnostic biomarkers for differentiation between ACC and ACA.