Abstract:

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.

Keywords: