A retrospective study of patients with myeloproliferative neoplasms (MPNs) provided evidence to support use of the combination of red blood cell (RBC) count and erythrocyte sedimentation rate (ESR) over either the hemoglobin level or the hematocrit value in the diagnosis and monitoring of patients with polycythemia vera (PV). The findings from this study were published in the European Journal of Haematology.
Although the WHO 2008 and 2016 diagnostic criteria for PV include elevated hemoglobin concentration levels in addition to the presence of a JAK2 mutation, controversy exists regarding the utility of the former criterion since it may be affected by PV-related iron deficiency, leading to falsely normal hemoglobin levels.
The hematocrit value, which is based on both the RBC count and the mean cell volume (MCV), has been suggested as an alternative to hemoglobin level in the diagnosis of PV. However, previous studies have provided evidence that iron deficiency-related microcytosis, which decreases the MCV, can falsely lower the hematocrit level. Conversely, hydroxyurea-related increases in MCV occurring during treatment of PV can potentially lead to unnecessary phlebotomy when the hematocrit value is used in the monitoring of patients with this disease.
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Some of the aims of this study were to evaluate the correlation between hematocrit value and RBC count in the setting microcytosis in a population of patients with PV and essential thrombocythemia (ET). In addition, the usefulness of ESR as a criterion for the diagnosis of PV was also evaluated.
Of the 182 patients from a single hematologic center included in this study, 39 had a diagnosis of PV, 27 had a diagnosis of ET, and 116 were classified as having a disease suspicious of MPN who were subsequently diagnosed with secondary erythrocytosis and secondary thrombocytosis (ie, MPN suspects).
Some of the key findings of this study were median hemoglobin concentrations of 185 g/L and 171 g/L in patients with PV and MPN suspects, respectively. Median hematocrit levels were similar in these 2 populations of patients: 0.55 and 0.5, respectively, although median ferritin levels were 44 µg/L and 110 µg/L in the 2 subgroups, respectively.
Compared with patients with PV, MPN suspects had significantly lower odds of a MCV less than 82 (odds ratio [OR], 0.16; 95% CI, 0.038-0.068) or a serum ferritin less than 15 µg/L (OR, 0.2; 95% CI, 0.52-0.74). No patients with ET had a MCV less than 82 or a ferritin level less than 15 µg/L.
In commenting on this finding, the study authors noted that the “hematocrit value must be interpreted carefully when being used for diagnosis of PV in patients with microcytosis.”
When patients with microcytosis were excluded from the analysis, the hemocrit levels and RBC counts were well correlated in both PV patients and MPN suspects. However, when patients with microcytosis were included, R2 values were 0.41 for those in the PV group compared with 0.66 for MPN suspects and 0.81 for patients with ET.
Regarding ESR, at a cutoff value of 2 mm separating positive (<2 mm) and negative (≥2 mm) ESR tests, the sensitivity and specificity for distinguishing patients with PV from MPN suspects were 37.1% and 97.7%, respectively.
The study authors noted that prospective trials are needed to validate the usefulness of RBC count and ESR as diagnostic biomarkers for PV.
Reference
Nersesjan V, Zervides KA, Sørensen AL, et al. The red blood cell count and the erythrocyte sedimentation rate in the diagnosis of polycythaemia vera. [published online October 4, 2019]. Eur J Haematol. doi: 10.1111/ejh.13334
This article originally appeared on Oncology Nurse Advisor
