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Permanent URI for this collectionhttps://hdl.handle.net/11443/932

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Author: search.filters.author.Ozgurtas, TanerHas files: Yes

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    Comparison of four immunoassay analyzers for relationship between thyroid stimulating hormone (TSH) and free thyroxine (FT4)
    (TURKISH BIOCHEM SOC, 2015-01-01) Serdar, Muhittin A.; Ispir, Emre; Ozgurtas, Taner; Gulbahar, Ozlem; Ciraci, Zahid; Pasaoglu, Hatice; Kurt, Ismail
    Objective: There is an inverse log/linear relationship between TSH and FT4 due to the negative feedback of these hormones on the pituitary. The objective of our study was to compare this relationship of TSH and FT4 between four different immunoassay analyzers. Methods: In our study, four data sets obtained from the database of four different hospital laboratories each using only a single method of measurement was used to evaluate this relationship between TSH and FT4. These data sets with their assay methods include: 21.102 test results measured by Modular E170 Analyzer (Roche Diagnostics, Germany), 20.241 test results measured by Access DxI 800 Unicel (Beckman Coulter, USA), 22.444 test results measured by Architect i2000sr (Abbott Laboratories, Abbott Park, Illinois, U.S.A) and 20.200 test results measured by ADVIA Centaur XP (Siemens Diagnostics, Tarrytown, NY). Inverse logarithmic relationship were determined from each data sets and compared between analyzers. Results: The correlation coefficients were -0.439 {[}95\% CI, (-0.450)- (-0.428)], -0.488 {[}95\% CI, (-0.498)- (-0.478)], -0.353 {[}95\% CI, (-0.364)- (-0.342)], -0.430 {[}95\% CI, (-0.441)- (-0.419)] for DxI 800 Unicel, Modular E 170, Architect i2000sr and ADVIA Centaur XP, respectively. In our study, all immunoassay analyzers showed poor correlation in a concentration range of TSH between 1.0 to 10.0 uIU/mL and the inverse log/linear relationship was not observed. Inverse relationship between TSH and FT4 is the result of negative thyroid pituitary hypothalamic feedback mechanism and this relationship is important especially in the diagnosis and treatment of hypo and hyperthyroidism. In data sets obtained from four different immunoassay analyzers, poor and statistically different correlation was observed between analyzers at TSH values ranged from 1.0 to 10.0 uIU/mL compared with FT4. Conclusion: These variations between analyzers may affect the clinical decisions especially in the evaluation of subclinical hypothyroidism, clinicians and laboratory specialists should be aware of these situation.
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    A practical ID-LC-MS/MS method for the most commonly analyzed steroid hormones in clinical laboratories
    (WALTER DE GRUYTER GMBH, 2019-01-01) Yesildal, Fatih; Serdar, Muhittin; Ozgurtas, Taner
    Background: Analysis of steroid hormones rapidly and reliably remains a challenge in clinical laboratories as this plays an important role in evaluation of many endocrine disorders. The aim of this study was to create a steroid profiling panel by using a liquid chromatography tandem mass spectrometry (LC-MS/MS) method which was composed of the most commonly analyzed steroid hormones in clinical laboratories. Materials and methods: Protein precipitation was performed for sample preparation. Ultra performance liquid chromatography (UPLC) system and an analytical column with C18 selectivity was chosen for chromatographic seperation. Atmospheric pressure chemical ionization (APCI) ion source was preferred for ionization, and tandem MS with triple quadrupole was used. MS scan was performed using the selected reaction monitoring mode in positive polarity. During the method validation process, test performance was evaluated for each steroid hormone, and 40 serum samples were used for method comparison with immunoassays available in our core laboratory. Results: An isotope dilution (ID)-LC-MS/MS method was developed, in which 13 steroids can be analyzed in the same run. Test performance was quite good for the 11 steroids (cortisol, DHEA, DHFAS, total testosterone, progesterone, androstenedione, 11-deoxycortisol, cortisone, corticosterone and dihydrotestosterone) while estradiol and aldosterone performance was suboptimal considering the precision and trueness. Conclusion: This ID-IC-MS/MS method would be useful in clinical laboratories, especially for the immunoassays having insufficient test performance and when checking for interferences in available immunoassays.