Dosages de prolactine Elecsys® et Kryptor® et macroprolactine

Numerous methods have been studied for macroprolactin screening. Among these methods, comparison of prolactin results obtained with a high-reading method, such as the Elecsys assay, with those obtained with a low-reading method could be a convenient one. Up to now, this approach has not been conclusive. Recent studies showed that, among all tested immunoassays, the Kryptor prolactin assay was the less sensitive to macroprolactin. This finding prompted us to undertake a comparison study between Elecsys and Kryptor prolactin results. We selected serum samples considered as negative for macroprolactin (PEG precipitated prolactin < 40%, n = 149) or as positive (precipitated prolactin ≥ 60 %, n = 149). Our results confirmed the low sensitivity of the Kryptor assay to macroprolactin. However, although we studied only samples clearly negative or positive according with the PEG precipitation result, we found a marked overlapping between the relative differences, (Elecsys-Kryptor)/Elecsys, calculated in the negative and positive groups. These findings are probably related to the heterogeneity of serum prolactin and macroprolactin and to the reactivity of the different molecular forms in the different immunoassays.