Platelet-rich plasma serotonin levels in chronic myeloproliferative disorders: evaluation of diagnostic use and comparison with the neutrophil PRV-1 assay

In a prospective study of 109 subjects, an enzyme-linked immunosorbent assay (ELISA) was used to measure platelet-rich plasma (PRP) serotonin levels in patients with polycythaemia vera (PV; n = 27), essential thrombocythaemia (ET; n = 14), myelofibrosis with myeloid metaplasia (MMM; n = 30), secondary or spurious polycythaemia (SP; n = 22) and controls (n = 16). Nine study subjects who were taking a selective serotonin reuptake inhibitor (SSRI) all displayed a markedly decreased PRP serotonin level (median, 24.2 ng/10(9) platelets; range, 0-49.3) and were therefore excluded from further analysis. Among the remaining 100 subjects, the median and range of PRP serotonin levels, in ng/10(9) platelets, was significantly lower in MMM (89.5; 0-278.3), PV (204.8; 0-496.0) and ET (385.3; 136.8-1025.7) compared with both SP (608.8; 369.0-1780.1) and controls (567.2; 359.9-1071.1). Neutrophil polycythaemia rubra vera-1 (PRV-1) expression was concurrently assayed by real-time polymerase chain reaction in 69 patients (23 PV, 17 SP, 12 ET, seven MMM, 10 controls). PRP serotonin measurement performed as well as the PRV-1 assay in distinguishing PV from SP (93% vs. 86% test accuracy). The current study suggests that PRP serotonin concentration might be considered as one of the several biological markers that complement each other for the diagnosis of PV.