Neutrophil-to-Lymphocyte Ratio Is More Accurate Than Erythropoietin Level for the Polycythemia Vera Diagnosis

Background Polycythemia vera (PV) is a myeloproliferative neoplasm (MPN). The MPNs are cancers in which the malignant clone triggers inflammatory cytokines, which sustain the inflammatory drive in a self-perpetuating vicious cycle. The current World Health Organization (WHO) criteria for PV diagnosis are gender-specific elevated hemoglobin or hematocrit levels, tri-lineage bone marrow hypercellularity, the presence of JAK2 V617F or JAK2 exon 12 mutation, and low serum erythropoietin (EPO) concentration. Below normal EPO continues to remain the only minor criterion for the PV diagnosis, although controversy exists regarding its predictive validity. The neutrophil-to-lymphocyte ratio (NLR) is a fast and simple method for assessing inflammatory status. While it is being studied as a useful predictive marker in many disease categories, not much research has been done on NLR in MPNs. In a previous study, we confirmed that the NLR was higher in MPN patients than in the normal population. Herein, we analyzed NLR in patients with PV and secondary polycythemia and studied whether it can be a marker to help diagnose PV. Furthermore, we compared the diagnostic capacity of NLR with that of the erythropoietin level.

Methods This retrospective case-control study included patients with erythrocytosis who have been tested for JAK2 between June 2007 and April 2022 at Soonchunhyang University Seoul and Bucheon hospitals. Diagnosis of PV was definitively ascertained by 2016 WHO criteria. NLR and EPO levels in patients with PV were compared to those in patients with secondary polycythemia at the time of diagnosis. The discriminatory power was calculated by area under the receiver operating characteristic curve analysis

Results Of 240 patients, 70 patients had a diagnosis of PV and 170 patients had a diagnosis of secondary polycythemia. The median NLR was significantly higher in PV group than in secondary polycythemia group (6.04 vs 1.77, p < 0.001). For diagnosing PV, the AUC value of NLR was better than that of EPO (0.921 vs 0.827, respectively). The model approximated by NLR with EPO had an AUC of 0.962 (95% CI, 0.936-0.988) for differentiating PV from secondary polycythemia, which was higher than individual components of the model used alone.

Conclusions We found that NLR is more accurate than EPO level for the PV diagnosis.

No relevant conflicts of interest to declare.