Association of a decreased platelet count with poor survival in patients with adult secondary hemophagocytic lymphohistiocytosis

Abstract Purpose We aimed to examine the association between baseline platelet count (PLT) and the prognosis of adult secondary hemophagocytic lymphohistiocytosis (sHLH). Material and methods Data from 292 patients with pretreatment platelet counts were retrospectively analysed from January 2016 to December 2020. We categorized platelet count into quartiles. Multivariable Cox proportional hazards models and restricted cubic splines (RCS) were used to evaluate the relationship between platelet count and mortality. Results During a median follow-up of 53 (interquartile ranges, 17–223) days, a total of 208 deaths occurred. After multivariable adjustment, a nonlinear and inverse relationship was observed for mortality (P for nonlinearity = 0.002). For non-LHLH, a similar curve was also observed (P for nonlinearity = 0.028). Decreased PLT ((PLT Q4)) was associated with an increased risk of mortality (adjusted hazard ratio: 1.97; 95% confidence interval: 1.28–3.04; Ptrend =0.005). Similar results were observed in the LHLH subgroup (adjusted hazard ratio: 1.84; 95% confidence interval: 1.05–3.24; Ptrend =0.024) but not in the non-LHLH subgroup (Ptrend =0.266). Conclusions: Baseline platelet count demonstrated a nonlinear and inverse association with an increased risk of mortality among adult sHLH patients. This method is used to identify sHLH patients with inferior overall survival due to its low cost and universal availability.