Detection of Macroprolactin Causing Hyperprolactinemia in Commercial Assays for Prolactin

Extract

To the Editor

John et al. (1) presented two clinical cases demonstrating the diagnostic confusion created by cases of hyperprolactinemia that are attributable to the presence of macroprolactin. The authors urged manufacturers of prolactin (PRL) reagents to (a) indicate in their product literature the extent to which macroprolactin interferes in their assays, and (b) have available a validated method to confirm the presence of macroprolactin. Considerable progress has been made in both of these issues since the distribution of serum from one of the cases presented by John et al. (1) by the United Kingdom National External Quality Assessment Scheme (UKNEQAS) (2); however, most of the data have been presented only in preliminary form. A more recent UKNEQAS distribution of a serum containing macroprolactin (2) provided data on more recently introduced assays, as well as on a wider range of assays (Table 1 ), and showed a pattern of reactivity in PRL assays similar to that presented by John et al. (1). The Roche Elecsys PRL assay (2) reacted strongly with macroprolactin in this sample, as indicated by product literature.