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Daily Medical Update
Erythrocytosis evaluation
Tuesday, June 30, 2026
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🔬 Practice-Changing Findings
Evidence from RCTs and meta-analyses published in the
last 12 months.
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Annals of Hematology (2026) - Retrospective diagnostic cohort
Key Findings
- Compared with ET, PV had lower median transferrin saturation index (12.9% vs 21.64%), ferritin (35.65 vs 95.05 ng/mL), and erythropoietin (2.23 vs 6.11 mIU/mL), while hemoglobin and hematocrit were increased in PV (all p = 0.001 or lower).
- Among JAK2-mutated cases, median JAK2 variant allele frequency was higher in PV than ET (48% vs 21%; p = 0.003) and correlated inversely with ferritin, transferrin saturation, and erythropoietin.
📋 Practice Implication: In borderline erythrocytosis with thrombocytosis, add transferrin saturation and JAK2 allele burden to the usual hemoglobin, hematocrit, and erythropoietin workup to sharpen discrimination between PV and ET.
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Annals of Hematology (2026) - Retrospective diagnostic study
Key Findings
- PV showed substantially higher median neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and systemic immune-inflammation index than secondary polycythemia (5.00 vs 1.86, 261.3 vs 94.0, and 2432.9 vs 368.8; p < 0.001 for all).
- Each inflammatory index differentiated PV from secondary polycythemia with sensitivity and specificity above 85% and area under the curve above 0.90.
📋 Practice Implication: When molecular testing is delayed or access is limited, markedly elevated inflammatory indices can justify faster hematology referral and confirmatory JAK2 testing.
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Blood Advances (2025) - Post hoc pooled randomized trial analysis
Key Findings
- Canagliflozin increased hematocrit and raised the 1-year prevalence of erythrocytosis versus placebo in males (16.9% vs 5.5%) and females (5.2% vs 1.0%).
- In males, higher baseline hematocrit modified treatment effect, with analysis showing benefit in anemia but increased harm in baseline erythrocytosis driven mainly by more myocardial infarction events; no similar heterogeneity was seen in females.
📋 Practice Implication: A medication review should specifically ask about SGLT2 inhibitors, especially in men with unexplained erythrocytosis or new arterial events, because the drug itself may be both the cause and a risk amplifier.
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The Journal of Sexual Medicine (2025) - Randomized controlled pilot trial
Key Findings
- In transgender men with testosterone-related secondary erythrocytosis, testosterone withdrawal lowered hematocrit more than dose reduction over 3 months (-3.5% vs -0.8%).
- Dose reduction preserved therapeutic testosterone levels and was accompanied by lower diastolic blood pressure, lower body weight, and lower anxiety scores, with no serious adverse events.
📋 Practice Implication: In testosterone-associated erythrocytosis, evaluation should document formulation and dosing interval because modest dose reduction may stabilize moderate hematocrit elevations without full hormone interruption.
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European Journal of Haematology (2026) - Nationwide population-based cohort
Key Findings
- Across 43,612 patient-years, advanced age and leukocytosis at diagnosis independently predicted thrombosis, major bleeding, and all-cause mortality in both PV and ET.
- Interferon-treated high-risk PV had reduced arterial event rates (2.21 per 100 patient-years), and interferon-treated high-risk ET had reduced arterial and venous event rates (1.55 and 0.44 per 100 patient-years).
📋 Practice Implication: Once primary erythrocytosis is identified, baseline leukocyte count and age should be captured as part of the initial evaluation because they inform early vascular risk counseling and follow-up intensity.
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Summary
Recent evidence on erythrocytosis evaluation emphasizes separating clonal PV from secondary causes with low erythropoietin, functional iron parameters, JAK2 burden, and inexpensive inflammatory indices, while a careful medication history remains essential because SGLT2 inhibitors and testosterone therapy can sustain elevated hematocrit. After diagnosis, contemporary cohort data show that age and leukocytosis still stratify vascular and mortality risk in PV and ET, supporting early risk-based monitoring alongside the diagnostic workup.
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