The uncertainty indicating reliability should be obtained in a universal and transparent fashion and should be combinable. GUM [2] approach, leading to a result without known bias and combined standard uncertainty, has unquestionable advantages over allowable total error concept, incorporating procedural bias. The answer is “roles for both” these concepts, but is necessary to differentiate between them. The author deals two critical notes to the “Recommendation of estimating uncertainty in measurements in laboratory medicine”[3].

        Key words: uncertainty, total allowable error; bias, treatment of uncorrected bias.