A simple clinical tool for effective screening of haemophagocytic lymphohistiocytosis in dengue.

Objective: Haemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder. Dengue fever is a common trigger for HLH in the tropics. We aimed to develop a simplified clinical tool to detect HLH in dengue patients.

Methods: A cross-sectional observational study was carried out at Kasturba Medical College Mangalore. Patients between 18 and 60 years of age, with dengue fever for more than five days with suspected HLH symptoms were selected. Hepatosplenomegaly, temperature, haemoglobin levels, total leucocyte count, platelet count, ferritin, triglyceride, and liver function tests were assessed. HLH-2004 criteria were used to confirm the diagnosis. A simple clinical tool was developed via decision tree analysis using clinical and laboratory parameters.

Results: Patients with HLH had marked leucopenia, thrombocytopenia, hyperferritinaemia and elevated aspartate aminotransferase levels, and a greater incidence of hepatosplenomegaly than those without HLH. Decision tree analysis was used to generate a clinical diagnostic tool, which demonstrated an accuracy of 94%, at a confidence interval of 95% (90-98%). The model's ability to predict HLH was 79%, while its specificity was 96%. It had a positive predictive value of 68% and a negative predictive value of 97%. The kappa value of the predicted model was 0.70, indicating an agreement with the diagnosis using HLH-2004 criteria, with a significant p-value (< 0.001).

Conclusions: Splenomegaly can be used as a screening method to diagnose HLH in patients with dengue. By using an algorithmic approach, combining splenomegaly with leucopenia and thrombocytopenia, this clinical tool accurately detects HLH in patients with dengue.