Long term false positive hsTnI on Alinity I probably caused by macrotroponin complex: Case report.

Elevated troponin levels are often indicative of various cardiac diseases; however, analytical interference can lead to false positive troponin concentrations. We present the case of a 48-year-old female patient with persistently falsely elevated high sensitivity troponin I (hsTnI) probably caused by the presence of macrotroponin. Laboratory testing included determination of hsTnI using various analytical methods, serial dilutions and determination of heterophilic antibodies and other autoimmune antibodies. Only precipitation with polyethylene glycol (PEG) indicated the presence of an interference by causing a significant decrease in hsTnI concentration. Our results suggest that the falsely elevated hsTnI concentration could be due to interference with the macrotroponin complex.

Corrigendum to: Assessment of antinuclear antibodies (ANA): National recommendations on behalf of the Croatian society of medical biochemistry and laboratory medicine.

[This corrects the article DOI: 10.11613/BM.2021.020502.].

Assessment of antinuclear antibodies (ANA): National recommendations on behalf of the Croatian society of medical biochemistry and laboratory medicine.

Antinuclear antibodies (ANA) represent a family of autoantibodies targeting ubiquitous cellular constituents and are a hallmark of systemic inflammatory autoimmune rheumatic diseases named connective tissue diseases (CTD). The gold standard method for ANA determination is indirect immunofluorescence (IIF) on the human laryngeal epidermoid carcinoma cell line type 2 substrate (HEp-2), but with increasing demand for ANA testing, novel methods eased for automation emerged, which allows testing by staff less experienced in this specific field of laboratory diagnostic. In 2016 The working group (WG) for laboratory diagnostics of autoimmune diseases as part of the Committee for the Scientific Professional Development of the Croatian Society of Medical Biochemistry and Laboratory Medicine (CSMBLM) published the data of a survey regarding general practice in laboratory diagnostics of autoimmune diseases in Croatia. Results indicated high diversity in the performance of autoantibody testing as well as reporting of the results and indicated the need of creating recommendations for the assessment of ANA that would help harmonize diagnostics of systemic autoimmune rheumatic diseases in Croatia. This document encompasses twenty-seven recommendations for ANA testing created concerning indications for ANA testing, preanalytical, analytical, and postanalytical issues, including rational algorithm and quality control assurance. These recommendations are based on the relevant international recommendations and guidelines for the assessment of ANA testing and relevant literature search and should help to harmonize the approach in ANA testing and clarify differences in interpretation of the results obtained using different methods of determination.

Comparison of diagnostic accuracy for eight SARS-CoV-2 serological assays.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological tests have been suggested as an additional diagnostic tool in highly suspected cases with a negative molecular test and determination of seroprevalence in population. We compared the diagnostic performance of eight commercial serological assays for IgA, IgM, and IgG antibodies to the SARS-CoV-2 virus. MATERIALS AND METHODS: The comparison study was performed on a total of 76 serum samples: 30 SARS-CoV-2 polymerase chain reaction (PCR)-negative and 46 SARS-CoV-2 PCR-positive patients with asymptomatic to severe disease and symptoms duration from 3-30 days. The study included: three rapid lateral flow immunochromatographic assays (LFIC), two enzyme-linked immunosorbent assays (ELISA), and three chemiluminescence immunoassays (CLIA). RESULTS: Agreement between IgM assays were minimal to moderate (kappa 0.26 to 0.63) and for IgG moderate to excellent (kappa 0.72 to 0.92). Sensitivities improved with > 10 days of symptoms and were: 30% to 89% for IgM; 89% to 100% for IgG; 96% for IgA; 100% for IgA/IgM combination; 96% for total antibodies. Overall specificities were: 90% to 100% for IgM; 85% to 100% for IgG; 90% for IgA; 70% for IgA/IgM combination; 100% for total antibodies. Diagnostic accuracy for IgG ELISA and CIA assays were excellent (AUC ≥ 0.90), without significant difference. IgA showed significantly better diagnostic accuracy than IgM (P < 0.001). CONCLUSION: There is high variability between IgM assays independently of the assay format, while IgG assays showed moderate to perfect agreement. The appropriate time for testing is crucial for the proper immunity investigation.

Current laboratory and clinical practices in reporting and interpreting anti-nuclear antibody indirect immunofluorescence (ANA IIF) patterns: results of an international survey.

BACKGROUND: The International Consensus on Antinuclear Antibody (ANA) Patterns (ICAP) has recently proposed nomenclature in order to harmonize ANA indirect immunofluorescence (IIF) pattern reporting. ICAP distinguishes competent-level from expert-level patterns. A survey was organized to evaluate reporting, familiarity, and considered clinical value of ANA IIF patterns. METHODS: Two surveys were distributed by European Autoimmunity Standardization Initiative (EASI) working groups, the International Consensus on ANA Patterns (ICAP) and UK NEQAS to laboratory professionals and clinicians. RESULTS: 438 laboratory professionals and 248 clinicians from 67 countries responded. Except for dense fine speckled (DFS), the nuclear competent patterns were reported by > 85% of the laboratories. Except for rods and rings, the cytoplasmic competent patterns were reported by > 72% of laboratories. Cytoplasmic IIF staining was considered ANA positive by 55% of clinicians and 62% of laboratory professionals, with geographical and expertise-related differences. Quantification of fluorescence intensity was considered clinically relevant for nuclear patterns, but less so for cytoplasmic and mitotic patterns. Combining IIF with specific extractable nuclear antigens (ENA)/dsDNA antibody testing was considered most informative. Of the nuclear competent patterns, the centromere and homogeneous pattern obtained the highest scores for clinical relevance and the DFS pattern the lowest. Of the cytoplasmic patterns, the reticular/mitochondria-like pattern obtained the highest scores for clinical relevance and the polar/Golgi-like and rods and rings patterns the lowest. CONCLUSION: This survey confirms that the major nuclear and cytoplasmic ANA IIF patterns are considered clinically important. There is no unanimity on classifying DFS, rods and rings and polar/Golgi-like as a competent pattern and on reporting cytoplasmic patterns as ANA IIF positive.

Quality and best practice in medical laboratories: specific requests for autoimmunity testing.

Special conditions associated with laboratory autoimmune testing are not well compatible with recent developments in regulatory frameworks such as EN/ISO 15189 accreditation or in vitro diagnostic medical device regulation (IVD-R). In addition, international recommendations, guidelines and disease criteria are poorly defined with respect to requirements on autoantibody testing. Laboratory specialists from Austria, Belgium, Croatia, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Norway, Poland, Portugal, South Africa, Spain, Sweden, Switzerland, and The Netherlands collected information, reported national experience, and identified quality issues in relation to autoantibody testing that require consensus on interpretation of the regulatory frameworks and guidelines. This process has been organized by the European Autoimmunity Standardisation Initiative (EASI). By identifying the critical items and looking for a consensus, our objective was to define a framework for, in particular, EN/ISO accreditation purposes. Here, we present a review of current publications and guidelines in this field to unify national guidelines and deliver in this way a European handout on quality control and accreditation for laboratories involved in autoantibody testing. We focus on quality items that can be checked during accreditation visits. Despite various local varieties, we encountered an overwhelming dedication to quality assurance in all contributing countries.

Interference of M-protein on Thrombin Time Test: A Case Report.

OBJECTIVE: A case of interference of monoclonal protein (M-protein) on thrombin time (TT) test in a 39-year-old Caucasian male patient is presented. METHODS: Coagulation screening tests were performed where altered results only for TT result (>150 seconds) and activated partial thromboplastin time (aPTT) result (36 seconds) were measured. Further specific coagulation testing included measurement of individual coagulation factors FII, FV, FVII, FVIII, FIX, FX, FXI, and FXII. Diagnostic steps in detection and identification of monoclonal protein included serum protein electrophoresis and immunofixation (both serum and urine specimen). RESULTS: Monoclonal protein immunoglobulin G kappa detection and identification in serum and urine clarified the situation. CONCLUSION: Unexpectedly altered results of screening coagulation tests without any appropriate clinical signs and symptoms in a patient without any anticoagulant therapy needs to be critically considered in the context of extended next diagnostic steps in order to clarify the cause of pathological test results.

α-1 Antitrypsin Genotype-Phenotype Discrepancy in a 42-Year-Old Man Who Carries the Null-Allele.

BACKGROUND: Alpha-1-antitrypsin (A1AT) deficiency is a hereditary condition caused by mutations in the SERPINA1 gene and associated with lung emphysema and liver disease. Laboratory testing in suspected A1AT deficiency involves quantifying serum A1AT concentration and identification of specific alleles by genotyping and phenotyping. The aim of this report was to present a case of the null allele carrier with consequent genotype/phenotype/concentration discrepancies and potential misclassification of the Z variant in a 42-year-old white man presenting with symptoms of chronic obstructive pulmonary disease (COPD). METHOD: Serum A1AT concentration was measured using an immunoturbidimetric assay. A1AT phenotype was determined using isoelectric focusing followed with immunofixation (IEF-IF). Genotyping specifically for the S and Z allele was performed by melting curve analysis using real-time PCR and checked by an alternative PCR-RFLP method. Genotype/phenotype ambiguity and discrepancy were amended using gene sequencing. RESULTS: Laboratory testing revealed highly reduced A1AT concentration (less than 0.30 g/L), mild to moderate deficient genotype (Pi*Z allele: M/Z and Pi*S allele: M/M) and severe deficient Z homozygous phenotype (Pi ZZ). After repeated sampling, the same discordant results were verified by these tests. Further sequencing revealed two clinically relevant and defective variants: rs199422210 (a rare null allele) and rs28929474 (the Z allele). CONCLUSION: Due to inability of genotyping kit probes to detect null/Z allele combination (which mimics the Pi ZZ phenotype), our patient was misclassified as mild to moderate deficient Pi*MZ heterozygote. In all unclear cases, whole-gene sequencing is highly recommended in order to determine definitive cause of A1AT deficiency.

Faecal calprotectin determination: impact of preanalytical sample treatment and stool consistency on within- and between-method variability.

INTRODUCTION: We assessed the differences in faecal calprotectin (FC) concentrations measured by two assays depending on the stool consistency and extraction method. MATERIALS AND METHODS: Stool samples were extracted using the EliA Stool Extraction Kit, Calex® Cap extraction device and respective weighing methods, while FC concentrations were measured using the EliATM Calprotectin and Bühlmann fCAL® Turbo method and checked for within- and between-method variability with regard to extraction method and stool consistency category. Extraction yield was evaluated for impact of different sample incubation time (10 min and 1 h) in extraction buffer for both methods and for impact of different initial sample dilutions (1:50, 1:100, 1:500) for fCAL® Turbo method. RESULTS: Results determined from Calex® Cap extracts were higher compared to weighing method extracts (mean bias 33.3%; P < 0.001), while no significant difference was found between results obtained with EliA Stool Extraction Kit and weighing method (mean bias 0.1%; P = 0.484), in both cases irrespective of stool consistency. Bühlmann fCAL® Turbo results were higher than EliATM Calprotectin results (mean bias 32.3%, P = 0.025 weighing method; and mean bias 53.9%, P < 0.001 extraction devices), the difference is dependent on stool consistency and FC concentration. Significantly higher FC extraction yield was obtained with longer sample incubation time for both methods (P = 0.019 EliATM Calprotectin; P < 0.001 fCAL® Turbo) and with increasing initial sample dilution for fCAL® Turbo method (P < 0.001). CONCLUSION: Preanalytical stool sample handling proved to be a crucial factor contributing to within- and between-FC assay variability. Standardization is urgently needed in order to assure comparable and reliable FC results.

Comparison of Enzymatic Assay for HBA1C Measurement (Abbott Architect) With Capillary Electrophoresis (Sebia Minicap Flex Piercing Analyser).

OBJECTIVE: To compare the analytical performances of the enzymatic method (EM) and capillary electrophoresis (CE) for hemoglobin A1c (HbA1c) measurement. METHODS: Imprecision, carryover, stability, linearity, method comparison, and interferences were evaluated for HbA1c via EM (Abbott Laboratories, Inc) and CE (Sebia). RESULTS: Both methods have shown overall within-laboratory imprecision of less than 3% for International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (<2% National Glycohemoglobin Standardization Program [NGSP] units). Carryover effects were within acceptable criteria. The linearity of both methods has proven to be excellent (R2 = 0.999). Significant proportional and constant difference were found for EM, compared with CE, but were not clinically relevant (<5 mmol/mol; NGSP <0.5%). At the clinically relevant HbA1c concentration, stability observed with both methods was acceptable (bias, <3%). Triglyceride levels of 8.11 mmol per L or greater showed to interfere with EM and fetal hemoglobin (HbF) of 10.6% or greater with CE. CONCLUSION: The enzymatic method proved to be comparable to the CE method in analytical performances; however, certain interferences can influence the measurements of each method.

Diagnostic and prognostic role of resistin and copeptin in acute ischemic stroke.

OBJECTIVES: Our aim was to evaluate (i) whether there is a difference in the concentration of resistin and copeptin between acute ischemic stroke patients and stroke-free controls; and (ii) if there is any prognostic value of resistin and copeptin in predicting stroke infarct volume, stroke severity, and outcome. METHODS: Our case-control study has recruited 112 acute ischemic stroke patients admitted within 24 h after the stroke onset. We have also included 63 age and gender matched stroke-free controls. Resistin and copeptin levels were measured by a commercial ELISA kits. Stroke severity was assessed according to the modified National Institute of Health Stroke Scale (mNIHSS) and the degree of disability was assessed using Barthel index (BI). Stroke infarct volume was determined by the volumetric estimation. RESULTS: Resistin concentrations were significantly higher in patients (3.2 mg/L; IQR: 1.9-6.4) than in stroke-free controls (2.5 mg/L; IQR: 1.4-5.2; p = 0.024) whereas the concentration of copeptin did not differ between patients and controls. Copeptin concentrations were significantly higher in patients with poor functional outcome (Barthel index <60) (p = 0.021). There was a significant negative correlation between copeptin and BI score (ρ = -0.309, p = 0.020). DISCUSSION: Resistin, but not copeptin levels are higher in acute ischemic stroke patients early after the stroke onset, than in age and gender matched stroke-free controls. Moreover, higher copeptin concentrations are predictive of poor short term functional outcome after ischemic stroke. If confirmed in larger prospective studies, resistin and copeptin could improve clinical diagnosis of stroke and effective management of patient recovery.

Can cranberry extract and vitamin C + Zn supplements affect the in vivo activity of paraoxonase 1, antioxidant potential, and lipid status?

BACKGROUND: The modern way of life exposes us to substantial oxidative stress, putting the focus on the research of antioxidant effects of dietary supplements. Recent studies have shown that the effectiveness of particular vitamins and herbal preparations might have an effect on paraoxonase activity. Paraoxonase 1 is an HDL associated enzyme which prevents the oxidation of LDL. Several studies have shown the beneficial effect of some dietary components to the activity of paraoxonase. The aim of this study was to analyze the effects of cranberry extract and vitamin C and zinc preparations (vitamin C + Zn) on serum paraoxonase 1 activity, antioxidant status, and glucose and lipid concentration. METHODS: The study included 31 healthy volunteers (median age 24 years). They were divided into 3 groups according to the intervention type and smoking status and exposed to commercially available preparations of the cranberry extract (2 g/day) and vitamin C + Zn (300 mg/day) during 4 weeks. RESULTS: The results have shown that there is a significant increase in the activity of the paraoxonase 1 in nonsmokers after the intervention with the cranberry extract as well as with vitamin C + Zn preparations. Also, total antioxidant status increased in the non-smokers subgroup after intervention with vitamin C + Zn. However, the lipid profile did not change significantly in response to antioxidant preparations. CONCLUSIONS: Our results show that antioxidant supplements can increase the antioxidant potential of an organism as well as paraoxonase 1 activity. This observation is pointing to the potential complementary role of dietary supplements in the primary prevention of atherosclerosis.

Antibodies targeting mutated citrullinated vimentin in patients with psoriatic arthritis.

Antibodies against mutated citrullinated vimentin (anti-MCV) are of a comparable diagnostic value in rheumatoid arthritis (RA) as antibodies targeting citrullinated peptides (anti-CCP). Anti-CCP are present in up to 15% of psoriatic arthritis (PsA) patients, while the prevalence of anti-MCV in PsA patients has been poorly investigated. The aim of the present study was to assess the prevalence and relevance of anti-MCV antibodies in PsA patients. The study included 56 PsA patients. Clinical features, disease activity, and functional ability were noted by an experienced rheumatologist. Serum samples of all patients were analyzed for anti-MCV and anti-CCP antibodies using enzyme-linked immunosorbent assay. Data on 92 patients with RA, 44 patients with other inflammatory rheumatic diseases, and 107 healthy controls from a previous study were used to compare the prevalence of anti-MCV antibodies in PsA patients. Anti-MCV antibodies were positive in only two out of 56 (3.6%) PsA patients, which was significantly lower compared to RA patients (63%). The anti-MCV level was moderately positive and borderline in one patient each. Both patients had asymmetric polyarthritis, dactylitis, moderate to high disease activity, and were anti-CCP and rheumatoid factor (RF) negative. There was no significant difference in anti-MCV levels according to clinical subtypes of PsA and no correlation of anti-MCV levels with anti-CCP, RF, disease activity variables, and functional ability indices. According to study results, anti-MCV antibodies can be detected in a very small proportion of PsA patients with polyarthritic disease and are primarily related to the polyarthritic pattern rather than the specific diagnosis of RA.

Matrix metalloproteinases and their inhibitors in different acute stroke subtypes.

The aim of the study was to determine serum levels of selected matrix metalloproteinases (MMPs) and their natural inhibitors (TIMPs) in the acute phase of different stroke types subdivided according to the Oxfordshire Community Stroke Project (OCSP) classification and the possibility of discriminating stroke types according to their levels. The study included 126 patients with acute stroke within the first 24 h of symptom onset, and 124 healthy volunteers. The stroke group had lower MMP-2 concentrations and MMP-2/TIMP-2 ratios (p<0.001) but higher TIMP-2 (p<0.001) than controls. The level of MMP-9 and the MMP-9/TIMP-1 ratio were higher in patients with total anterior circulation infarct (TACI) than in patients with other stroke subtypes according to OCSP classification (p=0.0019, p=0.0065, respectively) or in controls (p<0.0001, p=0.0024, respectively). A negative correlation of MMP-2 levels with MMP-9 and MMP-9/TIMP-1 ratio was recorded in all stroke subtypes except for TACI. Receiver operating characteristic analysis showed similar discriminating power for MMP-9 levels and Barthel index in the differential diagnosis of TACI. High MMP-9/TIMP-1 ratio (odds ratio 3.263) was associated with TACI. Our results demonstrate that the MMP-9/TIMP-1 ratio may provide information to help in assessing stroke patients in the future as a baseline biomarker of infarct extent.