Objective: High Performance Liquid Chromatography (HPLC) is widely used to classify hemoglobin fractions in screening of hemoglobinopathies. We, here in this study, detected the “measurement uncertainty” of the pivotal parameter in thalassemia screening, namely HbA2; and assumed its value in the laboratory test results.

Materials and Methods: HbA2 analysis was measured by HPLC analyser Tosoh HLC-723 G8 instrument, which works in cation exchange principle, in Antalya Research and Education Biochemistry Laboratory. Measurement uncertainty calculations were made according to the Nordtest manuals, using internal, and external quality control values.

Results: The measurement uncertainty for HbA2 was ±12.4% within a 95% coverage probability. The cut-off value used in our laboratory for a positive screening result is 3.5%. Our cut-off value should better be presented as 3.5±0.4% after the measurement uncertainty is included.

Conclusions: Although HbA2 measurement is important parameter in the screening of thalassemia, the literature lacks studies of measurement uncertainty of this parameter. Each laboratory should define their own measurement uncertainties not only to set their quality goals, but also in order to verify their capability to aid in clinical decisions.