Biochemia medica最新文献

Hereby we describe a case of a 59-year-old female patient with persistently elevated high-sensitivity troponin I (hs-TnI) over the course of almost four years measured on Alinity i with the corresponding assay (Abbott Laboratories, Chicago, USA). The patient underwent multiple extensive cardiological evaluations, but none of them suggested acute or chronic cardiac damage. Therefore, interference in measurement was suspected by the attending cardiologist and a detailed, stepwise laboratory investigation was undertaken in the sample with initial hs-TnI result of 2077 ng/L. Serial sample dilutions (1:2,1:5,1:10) did not match the expected, calculated hs-TnI concentrations, yielding both huge positive biases (62, 109 and 139%, respectively) and absolute differences (639, 453 and 290 ng/L, respectively). Precipitation with polyethylene-glycol, pretreatment in heterophilic blocking tubes (HBT) and immunoglobulin G depletion yielded hs-TnI results below the assay's diagnostic cut-off (< 15.6 ng/L). Alternate hs-TnI immunoassays (Siemens Healthineers, Beckman Coulter and Snibe) and measurement with the high-sensitivity troponin T (hs-TnT) assay yielded results below assays' specific cut-off values. This investigation confirmed that results of hs-TnI obtained by the Abbott assay were spuriously elevated. Significant lowering of hs-TnI after HBT pretreatment indicated that heterophile antibodies are the most probable source of interference. Based on this finding, it was entered in the patient's medical record that future determinations of cardiac troponin should be performed with an alternate hs-TnI or hs-TnT assay. This case emphasizes that analytical interferences are usually immunoassay-dependent. Evaluation of laboratory results in the clinical context and close collaboration between laboratory and clinical staff is crucial for their recognition.

The family of antineutrophil cytoplasmic antibodies (ANCA) includes autoantibodies targeting proteins within the primary granules of neutrophils and lysosomes of monocytes. So far, proteinase 3 (PR3) and myeloperoxidase (MPO) are considered clinically relevant ANCA specificities. National recommendations for the assessment of ANCA are the outcome of the survey done by the Working group (WG) for laboratory diagnostics of autoimmune diseases of the Croatian Society of Medical Biochemistry and Laboratory Medicine (CSMBLM), where the diversity in the performance of ANCA testing and reporting among the laboratories in Croatia was observed. This document contains recommendations concerning the indications for ANCA testing, preanalytical, analytical and postanalytical issues, including rational algorithm and quality control assurance. The recommendations are based on the International consensus on ANCA testing and reporting as well as other relevant literature in order to help to harmonize ANCA testing. The aim of these recommendations is to improve and harmonize ANCA testing among laboratories in Croatia.

Creatine kinase (CK) activity has been generally considered as reliable blood marker for assessing muscle function, damage, and repair. However, the greatest challenge in the interpretation of CK activity remains the high variability in CK increase in relation to degrees of muscle cell damage or disturbance. Several known contributors to CK variability have been identified. The most important include the type of training, exercise intensity, gender differences, body composition, intra- and interindividual biological variability, as well as preanalytical and analytical considerations. Creatine kinase variability following different types of exercise reflects the complex interplay between exercise modality, intensity, individual physiology, and recovery strategies. High-intensity exercises, especially those involving eccentric muscle contractions, tend to produce more significant CK responses due to greater muscle fiber disruption. Gender differences in CK variability are pronounced, with men generally exhibiting higher CK activities following exercise compared to women. Creatine kinase variability is also closely linked to body composition, with muscle mass generally leading to higher CK activities post-exercise, while higher body fat may correlate with lower CK responses. Regarding preanalytical and analytical considerations, perhaps the greatest challenge in CK measurement is the limited sample stability, which should always be taken into consideration when analyzing CK activity in stored samples for research or clinical purposes. This review, through exploring all of the above-mentioned sources of CK variability, could facilitate the development of evidence-based practices for preventing overuse injuries, and promoting long-term athlete health and well-being.

For decades, bilirubin was thought to be merely a degradation product of the hem, a potentially toxic compound and a molecule with no specific physiological function. Recently, it has been discovered that bilirubin has a strong antioxidant effect and possesses molecular signalling, hormonal and immunomodulatory properties. Numerous studies show that moderately elevated serum bilirubin concentrations correlate with a lower risk of developing pathological conditions mediated by oxidative stress and inflammation. Low concentrations within the current reference interval have been shown to be a potential risk factor for various pathological conditions. It is to be expected that knowledge about bilirubin will lead to the determination of bilirubin concentration gaining new importance in diagnostics, for example as a prognostic marker, but also as a therapeutic molecule.

Introduction: A control chart based on Hotelling's T² multivariate statistics was used to monitor the quality of an immunoenzymatic assay for plasma levetiracetam. The chart incorporated a multi-level quality control (MLQC) system with three concentration levels of the analyte and included the analytical performance specification (APS) for therapeutic drug monitoring.

Materials and methods: Data were collected from March 1 to August 14, 2024, comprising 84 consecutive triplets of values for the three MLQC levels. The initial 59 triplets were used to estimate the variance-covariance matrix and vector of means (phase I). These estimates were then applied to calculate Hotelling's T² for the remaining 25 triplets (phase II). The pharmacokinetic model of Fraser was employed to derive the APS for levetiracetam, based on a twice-daily dosing scheme and a median half-life of 8 hours.

Results: The three MLQC levels showed significant correlations (r > 0.6) in both control phases. The Hotelling's T² control chart detected no out-of-specifications states (OC), compared to 12 OC signals from individual Levey-Jennings charts monitoring the MLQC levels separately. The integration of the APS into the Hotelling's T² chart provided additional insights into the process quality, and in two instances, it aligned with the OC signal from at least one of the Levey-Jennings charts.

Conclusions: Hotelling's T² multivariate chart is effective for internal quality control of laboratory tests. As MLQC data offer correlated information, this approach is advantageous over multiple individual univariate charts as it ensures the correct level of false positive and false negative alarms.

Introduction: 25-hydroxyvitamin D (25-OH-D) is essential for calcium homeostasis and bone health, with increasing evidence suggesting associations with non-skeletal diseases. However, the lack of consensus on optimal concentrations and laboratory variability has led to clinical uncertainty and excessive testing. This study evaluates the impact of demand management strategies and revised cut-off points on test volumes, unperformed determinations, and cost savings.

Material and methods: A retrospective study (January 2015-May 2024) analyzed all 25-OH-D requests. Concentrations of 25-OH-D were measured using electrochemiluminescence assays on a Cobas C8000. An annual trend analysis of 25-OH-D test requests was performed to evaluate changes in demand. In 2018, vitamin D deficiency prevalence was assessed according to three cut-off values (75, 50 and 30 nmol/L). We assessed the impact of demand management rules, implemented in May 2022, to reduce unnecessary testing. The follow-up testing rate was calculated as the proportion of repeat tests within 12 months after determination.

Results: There was 25-OH-D testing increased from 10,830 in 2015 to nearly 85,000 in 2023. Demand management strategies led to 12,406 rejections in 2022 (from May onwards), 16,809 in 2023, and 7566 in 2024 (until May), saving €85,600. Follow-up testing rates dropped from ~15% before 2022 to ~5% afterward. Lowering the deficiency threshold from 75 to 50 nmol/L reduced deficiency diagnoses from > 70% to < 50%; at 30 nmol/L, rates could drop to ~10-11%.

Conclusions: Demand management strategies effectively reduce unnecessary testing and healthcare costs. Establishing appropriate reference values prevents overestimation of vitamin D deficiency, optimizing clinical and economic outcomes.

Introduction: Serum neuron specific enolase (NSE) is used as neuroendocrine tumor and central nervous system damage marker. It is present in variable concentrations in erythrocytes and hemolysis interferes in serum NSE quantification. Our aim was to develop a correction formula for moderate hemolysis, based on repeated patient samples instead of artificial sample doping with hemolysates.

Materials and methods: We searched in laboratory informatics system for patients with sample pairs obtained within 24 h, for NSE quantification. We registered NSE and hemolytic index (NSE1 and HI1) from the first moderate hemolyzed sample (HI: 15-80), and from the second non-hemolyzed sample obtained afterwards (NSE2 and HI2). In a development cohort (N = 41), we obtained the formula NSE_calc = NSE1 - (0.354 x (HI1 - HI2)) - 0.162, which was later used in the validation cohort (N = 26) to calculate NSE corrected concentrations (NSE_calc).

Results: Concentrations of NSE2 differed from NSE1 (P = < 0.001) but not from NSE_calc (P = 0.291). In 84% samples, NSE1 had a relative bias from NSE that exceeded the 14% limit of total error allowable, with a median relative bias of 22.5%. Meanwhile, the bias between NSE2 concentrations and NSE_calc was - 0.4 µg/L (95% confidence interval = - 3.8 to 4.5), the relative bias was 8.3% and only 23% of samples exceeded the 14% limit. Formula usefulness was limited to moderate hemolytic samples.

Conclusions: In summary, with this innovative approach, the NSE_calc bias is low enough to have clinical significance, so re-drawings of blood samples might be avoided. This approach also opens the possibility to correct the estimation of other magnitude concentrations affected by in vitro hemolysis.

Introduction: Defining trustworthy reference intervals (RIs) for serum folate (FOL) or serum cobalamin (VITB12) is a difficult task. The purpose of this study is to use an indirect approach from the laboratory information's system to indirectly generate RIs for FOL and VITB12.

Materials and methods: A retrospective observational study was performed at a tertiary-care laboratory's hospital during 12 months. All FOL and VITB12 tests were measured using a Cobas8000 e801 system (Roche Diagnostics, Mannheim, Germany). The RIs were calculated using a non-parametric approach. The RIs established in the present study were verified by calculating the fraction of RIs that fell outside the new RIs, in two validation cohorts sampled using the direct and indirect method.

Results: A total of 19,214 (FOL) and 27,420 (VITB12) results were obtained. The RIs were 4.5 nmol/L (90% confidence intervals (CI) 4.4-4.6) to 38.4 nmol/L (CI 38.3-38.5) for FOL and 140 pmol/L (CI 139-141) to 659 pmol/L (CI 657-660) for VITB12. The verification included 8,798 FOL results and 7,365 VITB12 results. For both magnitudes was acceptable since only 0.1% of FOL and 0.02% of VITB12 results fell outside the RIs. Finally, the RIs were verified using a direct method with twenty individuals. For FOL 20/20 cases and 19/20 of VITB12 cases fell within the estimated RIs.

Conclusions: In summary, the use of an indirect data approach has enabled us to calculate RIs for FOL and VITB12. The RIs obtained in our study are lower than those proposed by the manufacturer for both FOL and VITB12.

This case report investigates the occurrence of green discoloration in serum and citrate plasma samples collected from a male adult patient following a multivisceral organ transplant. In collected samples, it was necessary to investigate the influence of sample discoloration on the results of laboratory tests and to determine the appropriate approach to sample management. Hematology, coagulation and blood gas analysis showed no flags, but the biochemical lipemia index was susceptible to positive interference, necessitating dilution of the native sample. Despite the green discoloration, both native and diluted samples exhibited minimal interference on routine clinical chemistry analyses, demonstrating the reliability of the laboratory test results. This case report underscores the influence of preanalytical factors on the results of laboratory tests, the need for a thorough assessment of the sample adequacy for laboratory testing and the strict application of appropriate guidelines in the sample management in order to make an accurate diagnosis and ensure optimal patient care.

Autovalidation is a computerised postanalytical tool that uses a sequence of procedures to verify laboratory test results without manual intervention. The Working Group for Post-analytics of the Croatian Society for Medical Biochemistry and Laboratory Medicine has prepared procedures for the implementation of autovalidation in routine laboratory work, which complement the existing national recommendations and aim to clarify the procedures of autovalidation. Before implementation, it is necessary to determine the need for the introduction of autovalidation in routine laboratory work, and then appoint the autovalidation team, whose task is to decide in which area of laboratory work autovalidation should be introduced, create the algorithm and supervise the verification of autovalidation. Standard rules included in the algorithm are patient data, messages from the analyzer, values of interference indices, autovalidation range and delta check. All criteria defined in the autovalidation algorithm have to be documented and approved by the laboratory manager. This autovalidation procedure shows the basic rules of autovalidation that can be used by any laboratory in the initial phase. The justification for using autovalidation will depend on the number and complexity of laboratory tests, the size of the laboratory personnel, and the available financial and material resources. Autovalidation avoids the subjective evaluation of laboratory test results as it is based on the same rules and is standardised to a certain extent, which further increases the quality of laboratory test results.