Une alternative à  la chromatographie pour la détection de la macroprolactine : calcul du rapport de deux immunodosages de la prolactine : Immulite 2000® et Kryptor®

Macroprolactin is a high molecular mass form of prolactin with minimal bioactivity in vivo. The presence of macroprolactin must be considered for the differential diagnosis of hyperprolactinemia because prolactin-immunoassays present various reactivity with macroprolactin. So we compared to the reference technique (size-exclusion chromatography) a new screening test: calculation of the ratio between results obtained from two prolactin assays: Immulite® with high cross reactivity with macroprolactin and Kryptor® with no reactivity. In this study, serums from 69 patients with various macroprolactinemia (between 8 and 88% with chromatography) were selected and the ratio of the results of two prolactin assays was calculated for 49 hyperprolactinemic serums (prolactinemia > 636 mUI/l, Immulite 2000®). According to ROC curves analysis, a low Immulite®/Kryptor® ratio (< 1.45) indicates the presence of less than 20% of macroprolactin (sensitivity = 100% specificity = 85%), and a high ratio (> 1.80) indicates the presence of more than 50% of macroprolactin (sensitivity = 95%, specificity = 100%). However, this screening test must be confirmed by size-exclusion chromatography for the rare samples presenting an Immulite®/Kryptor® ratio between 1.45 and 1.80.