2021, Cilt 19, Sayı 1, Sayfa(lar) 032-040 |
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Cross-Reactivity in Thyroid Function Tests: A Tertiary Care Centre Experience |
Esra Fırat Oğuz1, Fatma Meriç Yılmaz2, Turan Turhan1, Canan Topçuoğlu1, Müjgan Ercan Karadağ3 |
1Ankara Şehir Hastanesi, Tıbbi Biyokimya, Ankara, Türkiye 2Yıldırım Beyazıt Üniversitesi Tıp Fakültesi, Tıbbi Biyokimya, Ankara, Türkiye 3Harran Üniversitesi Tıp Fakültesi, Tıbbi Biyokimya, Şanlıurfa, Türkiye |
Keywords: immunoassay, interference, thyroid function tests, cross-reactivity, heterophilic blocking tube |
Aim: Cross-reactivity in immunological techniques varies and the frequency depends on the population
of the study, technique for detecting the reaction and researcher’s method. In this study our aim was to
evaluate the cross-reactivity in thyroid function tests.
Material and Methods: TSH, free T3 and freeT4 tests of 47915 patients were analyzed for eight
months. Suspected five samples were analyzed with DXI800 (Beckman Coulter, USA) and Cobas
e601(Roche Diagnostics, Germany) was used as an alternative device. Also serial dilution, polyethylene
glycol (PEG) precipitation and incubation with heterophilic blocking tubes (HBT, Scantibodies
Laboratory) were performed for TSH.
Results: The results of the tests performed on two different immunoassays were above the limits when
evaluated according to desirable bias and total allowable error (7.8% ve 23.7% for TSH, 4.8% ve 11.3%
for free T3, 3.3% ve 8% for free T4). After incubation with HBT, recovery rates were above 50% for all
samples. Linear curves had observed in serial dilution. After PEG precipitation; below 40% of recovery
had obtained in one sample, therefore it was defined as macro-TSH.
Conclusion: In the current study, we evaluated 5 suspected samples in 47915 and found one sample
considering interference. The difference of frequency from the literature (0.05% to 6%) may be due to
the variation in patient population, the immunological method used, and the observation period.
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