A composite splenomegaly and platelet score for thrombosis risk in myeloproliferative neoplasms in Saudi Arabia

Thrombosis is a major complication of myeloproliferative neoplasms (MPNs) and a leading contributor to morbidity and mortality, yet risk prediction data from the Middle East remain scarce, and the prevalence of silent asymptomatic thrombosis has not been well characterized. We conducted a two-center retrospective-prospective cohort study of 83 patients with Philadelphia chromosome-negative MPNs at King Faisal Specialist Hospital and Research Centre (KFSHRC), Jeddah ( n = 69) and Medina ( n = 14), Saudi Arabia (2015–2025), using 2022 WHO classification criteria. Across the full cohort, thrombosis occurred in 24 patients (28.9%), predominantly in the splanchnic/abdominal venous system (29.2%). Separately, as a prospective screening component, 45 consenting patients without previously known thrombosis underwent single-visit, comprehensive Doppler ultrasonography of the upper limbs, lower limbs, and abdominal vasculature to detect silent thrombosis. Thrombosis rates were virtually identical across both branches (Jeddah 29.0%, Medina 28.6%, p = 1.000). Splenomegaly was significantly more prevalent in thrombotic patients (70.8% [95% CI 50.8–85.1%] vs. 42.4% [95% CI 30.6–55.1%], p = 0.035). Baseline diagnostic platelet counts were paradoxically lower in the thrombosis group (median 393 vs. 682 × 10⁹/L, p = 0.020), driven by splenic sequestration - patients with splenomegaly had markedly lower baseline platelets than those without (412.5 vs. 800.0 × 10⁹/L, p = 0.005). A novel 2-variable composite score (splenomegaly + baseline PLT < 500 × 10⁹/L) produced a significant thrombosis gradient of 12.9, 33.3, and 45.5% across low, intermediate, and high-risk tiers ( p = 0.029; AUC 0.677 [95% CI 0.572–0.800]; bootstrap-corrected AUC 0.670). Established risk scores (r-IPSET-T, MIPSS-PV) demonstrated exploratory risk stratification. Systematic Prospective Doppler screening detected no new silent thrombosis (0%; 95% CI 0.0–7.9%), though larger studies are needed to definitively exclude low rates of silent thrombosis.