Carcinoembryonic antigen monitoring to detect recurrence of colorectal cancer: how should we interpret the test results?

study confirms the conclusion of Braga et al. (2 ) that the individuality in Hb A1c is limiting the use of outcome-based or populationbased reference limits for test interpretation and will therefore also limit the use of a fixed cutoff value of 48 mmol/mol (6.5% DCCT) for the diagnosis of diabetes for all individuals/patients. The reason for this is that a small change in Hb A1c may indicate a clinically significant change, e.g., development of diabetes in a patient, even if the difference between the 2 results does not cross the threshold. The CVwp of stable diabetic patients should especially be used for monitoring purposes. However, as shown by Carlsen et al. (3 ), the CVwp of stable diabetic patients does not differ significantly from that of healthy individuals, and therefore it is probable that the findings in this study will also refer to stable diabetes patients. In conclusion, the withinperson biological variation of Hb A1c in healthy individuals is very low compared with the betweenperson biological variation of Hb A1c, affirming the absolute individuality of Hb A1c. The data also suggest that population-based reference limits and fixed cutoff values should be more closely examined for the diagnosis of diabetes. CVs in DCCT units are lower than CVs in SI units and therefore cannot be directly compared.