Serum prolactin overestimation and risk of misdiagnosis

BACKGROUND: Falsely elevated prolactin measurements risk overdiagnosis, and unnecessary imaging and treatment. DESIGN: We conducted a clinical audit of 18 patients who presented with hyperprolactinaemia, followed by a laboratory audit of 40 split samples across a range of serum prolactin (5‐5051 mIU/L). In each case (total n = 58), serum prolactin was measured on both Roche and Siemens platforms. RESULTS: Serum prolactin as measured by Roche was higher than the corresponding Siemens value in every case, despite similar reference ranges. The mean discrepancy in serum prolactin by Roche vs. Siemens was +81% in the clinical audit and +50% in the laboratory audit. This led to unnecessary interventions in 7/18 patients (39%) in the clinical audit. CONCLUSIONS: Serum prolactin is overestimated on the Roche relative to the Siemens platform. Laboratories should review Roche reference intervals for serum prolactin, and clinicians should consider repeating serum prolactin on another platform if the serum prolactin is incongruent with the clinical scenario.