Objective: Test analyses in laboratories must leave neither clinician nor patient in doubt. Measurement uncertainty must therefore be studied for all tests in laboratories. The aim of this study was to calculate the measurement uncertainty of the hormone dehydroepiandrosterone sulfate (DHEA-S) and to raise the issue and discuss measurement uncertainty again.

Material and Methods: Measurement uncertainties in serum DHEA-S tests in male patients in our laboratory using the top down method were reported as identification of the subject measured, listing of the factors affecting measurement values, reproduction bias in the laboratory, laboratory and method bias measurement uncertainty, uncertainty deriving from calibration, uncertainty deriving from external quality control data, combined measurement uncertainty and expanded measurement uncertainty.

Results: 1. uRw2 = (RSDpathological low control2 + RSDnormal control2 + RSDpathological high control2): (1.112 + 1.372 + 5.762) / 3 = 12.09 2. [uCref = 0.47; Cref = 375.4; k = 2]. RuCref = (100 x uCref) / (k x Cref): (100 x 0.47) / (2 x 375.4) = 0.062; RuCref2 = 0.0039 3. ubias2 = RuCref2 + uEQA2: 0.0039 + 48.03 = 48.0339 4. Uc = √ (uRw2 + ubias2): √ (12.09 + 48.0339) = 7.75 5. U = 2√ (uRw2 + ubias2): 2 x 7.75 = 15.5%

Conclusion: The measurement uncertainty of DHEA-S at a 95% confidence interval is + 15.5%. In providing the results of these tests, measurement uncertainties must be calculated within international standardization rules. Measurement uncertainty is a value that indicates the dispersion of measurement results. If all laboratories calculate measurement uncertainty in all tests on an occasional basis this will bestow transparency on the evaluation of the results.