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    Evaluation of D-dimer levels measured by different analytical methods in COVID-19 patients
    (2022) Arslan, Fatma Demet; Başok, Banu İşbilen; Terzioğlu, Mustafa; Altan, Tuba Kansu; Karaca, Yeşer; Senger, Süheyla Serin; Çolak, Ayfer
    Clinicians experience some challenges due to the lack of standardization of test, although D-dimer is a prognostic marker for COVID-19. We compared the clinical and analytical performances of D-dimer results obtained from different devices, kits and methods in patients with a diagnosis of COVID-19. Thirty-nine patients with a diagnosis of COVID-19 and 24 healthy individuals were included in the study. D-dimer levels were measured with Innovance D-DIMER kit (immunoturbidimetric method) on Sysmex CS-2500 and BCS XP and VIDAS D-Dimer Exclusion II kit (enzyme-linked fluorescence method) on mini VIDAS. The studies of precision, method comparison and clinic performance were performed. The variation coefficients in all systems were within the acceptable imprecision (7.8%). Bias%(12.5%) between BCS XP and Sysmex CS-2500 was lower than the acceptable Bias%(15.5%). Bias% values (19.2% and 33.3%, respectively) between Mini VIDAS with BCS XP and Sysmex CS-2500 were higher than the acceptable Bias%. The correlation coefficients among all systems were 0.89-0.98. For 500 ng/ml FEU, there was almost perfect agreement between BCS XP and Sysmex CS-2500, a moderate agreement between Mini VIDAS and BCS XP and Sysmex CS-2500. The cut-off values for distinguishing between individuals with and without COVID-19 were Mini VIDAS, Sysmex CS-2500 and BCS XP 529, 380 and 390 ng/ml FEU, respectively. The immunoturbidimetric method can be used as an alternative to the enzyme-linked fluorescent method because of satisfactory agreement at the different thresholds proposed for venous thromboembolism. However, it is recommended to follow up COVID-19 with the D-dimer results obtained by the same assay system.
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    Measurement Uncertainty in Specific Hormone Tests
    (2023) Akşit, Murat; Terzioğlu, Mustafa; Altan, Tuba Kansu; Akşit, Merve Zeytinli; Çolak, Ayfer; Başok, Banu İşbilen
    Aim: Quality improvement studies in clinical laboratories play a vital role in achieving accurate and reliable patient results. Measurement uncertainty is important for the quality and reliability of test results. Since laboratory results inherently involve uncertainty, ISO 15189 Accreditation Standards recommend reporting patient results accompanied by measurement uncertainty. The aim of our study is to determine the measurement uncertainty and compare it with the total allowable error (TEa%) values determined by international organizations in order to increase the accuracy and reliability of the specific hormone tests studied in our laboratory. Material and Methods: Our study was conducted at the Medical Biochemistry Laboratory of Health Sciences University İzmir Tepecik Training and Research Hospital. To determine the measurement uncertainties of adrenocorticotropic hormone (ACTH), growth hormone, insulin-like growth factor-1 (IGF-1), C-peptide, thyroglobulin, 25-hydroxy vitamin D, and parathormone (PTH) parameters, the 3-month period from October to December 2022 internal quality control data and 12-month external quality control data from January to December 2022 were used. The measurement uncertainty of the tests was calculated according to the Nordtest guideline. These values were evaluated based on TEa% criteria established by three different international organizations. Results: The measurement uncertainties of ACTH, growth hormone, IGF-1, C-peptide, thyroglobulin, 25-hydroxy vitamin D, and PTH tests were 11.53, 14.83, 12.35, 7.91, 18.18, 20.95, 15.69 for level 1 at 95% confidence interval; for level 2, it was calculated as 10.99, 13.65, 13.15, 5.87, 17.24, 17.05, 16.56 respectively. The measurement uncertainties of the C-peptide, thyroglobulin, and PTH tests for level 3 were 6.98, 16.03, and 15.51, respectively. Conclusion: While the expanded measurement uncertainties of growth hormone and C-peptide were determined below the TEa% values determined by international organizations, the measurement uncertainties of the ACTH and IGF-1 tests were found to be borderline high compared to the Royal College of Pathologists of Australasia (RCPA) TEa% values at both levels. While the measurement uncertainties of thyroglobulin, 25-hydroxy vitamin D, and PTH parameters were higher than the RCPA TEa% values at both levels, they were found below the TEa% values determined by other international organizations.