Is there a clinical role of RBC/PLT and RDW/ PLT ratios in differentiating patients diagnosed with primary and secondary polycythemia

Objective : The objective of this study is to assess the clinical utility of the RBC/PLT and RDW/PLT ratio derived from routine complete blood count data as readily accessible, low cost, and practical markers for distinguishing PV from secondary polycythemia, given the limited availability, high cost, and prolonged turnaround time of genetic tests, as well as the invasive nature of bone marrow biopsy. The resulting data are anticipated to guide clinicians in identifying patients who require further evaluation for PV and to streamline the diagnostic workflow. Material–Methods: The diagnosis of PV was established according to the 2016 WHO criteria. Cases of polycythemia that did not meet these criteria were classified as secondary polycythemia. A total of 102 patients were included in the study, comprising 51 patients with PV and 51 with secondary polycythemia. Patients in the secondary polycythemia group were randomly selected from among polycythemic individuals to match the number of patients in the PV group. In this retrospective study, the clinical significance of the RDW/PLT and RBC/PLT ratios was evaluated in differentiating between PV and secondary polycythemia. Results: The RDW/PLT ratio was found to have no predictive value in distinguishing between PV and secondary polycythemia (AUC = 0.484; 95% CI: 0.368–0.600; p = 0.781). On the other hand, the RBC/PLT ratio was significantly higher in patients with secondary polycythemia compared to those with PV (p = 0.004). According to ROC) curve analysis, an RBC/PLT ratio of 0.018 was identified as a potential threshold for differentiating secondary polycythemia from PV, with a sensitivity of 88% and a specificity of 51% (AUC = 0.666; 95% CI: 0.557–0.775; p = 0.004). Conclusion: In our study, which aimed to investigate the clinical relevance of relationships between complete blood count parameters in the differential diagnosis of PV and secondary polycythemia, the RBC/PLT ratio was found to be significantly higher in patients with secondary polycythemia compared to those with PV. In contrast, the RDW/PLT ratio was not identified as a statistically significant parameter for distinguishing between these two patient groups. Keywords: Polycythemia vera, secondary polycythemia, RDW/PLT ratio, RBC/PLT ratio, reticulocyte distribution width, hemoglobin, hematocrit