Platelet Recovery and Mortality in Septic Patients with Thrombocytopenia: A Propensity Score-Matched Analysis of the MIMIC-IV Database

Background: Thrombocytopenia (platelet count < 100 × 10⁹/L) occurs in 20–40% of critically ill patients with sepsis and is associated with adverse outcomes. Most prior studies have treated thrombocytopenia as a static risk indicator rather than a dynamic process. We investigated whether platelet recovery within 7 days provides independent prognostic information in patients with sepsis. Methods: We performed a retrospective cohort study using the MIMIC-IV database. Among 22,513 adults with sepsis admitted to intensive care units, 5401 developed thrombocytopenia within 24 h of admission and had sufficient follow-up data. The primary exposure was sustained platelet recovery to ≥100 × 10⁹/L within 7 days. The primary outcomes were 28-day and in-hospital mortality. Propensity-score matching and overlap weighting were used to adjust for demographic characteristics, comorbid conditions, illness severity, and organ-support therapies. Results: Among 5401 septic ICU patients with thrombocytopenia, 3193 (59%) achieved platelet recovery within 7 days. A total of 2056 patients (38%) recovered by day 3, and 1137 (21%) recovered between days 4 and 7. After multivariable adjustment, platelet recovery was independently associated with markedly lower mortality (adjusted risk ratio, 0.56; 95% CI, 0.53–0.67 for in-hospital death; and 0.60; 95% CI, 0.53–0.67 for 28-day death) and more than a doubling of survival time (adjusted ratio, 2.08; 95% CI, 1.65–2.63). Early and intermediate recovery conferred similar benefits. Higher baseline platelet counts, antiplatelet therapy, and heparin use were associated with recovery, whereas cirrhosis, greater illness severity, and continuous renal replacement therapy were associated with non-recovery. Conclusions: In patients with sepsis and thrombocytopenia, platelet recovery within 7 days was a strong and independent predictor of survival. Exploratory timing-stratified analyses yielded similar associations across subgroups. These findings support platelet recovery as a useful prognostic marker reflecting broader physiologic stabilization in sepsis.