Serum soluble interleukin-2 receptor (sIL-2R) is an accurate biomarker for dengue-associated hemophagocytic lymphohistiocytosis syndrome diagnosed by Hscore

Objective: Hemophagocytic lymphohistiocytosis is a potentially fatal complication of severe dengue fever. Here we evaluated the serum soluble IL-2R levels as potential biomarker for identifying HLH in patients with dengue fever. Methods: In this cross-sectional study conducted in a tertiary care center of a teaching hospital, subjects with dengue and fever of more than 5 days, leukopenia/thrombocytopenia and/or hepatosplenomegaly were studied. Data were collected to compare sIL-2R values and serum ferritin with Hscore and Histiocyte Society 2004 criteria. Relevant statistical methods were used. Results: 80 subjects with severe dengue fever were analyzed with relevant investigations. Mean H score was 219.2 ± 17.6 in 18 dengue patients with HLH v/s 166.2 ± 11.2 in 62 patients without HLH (p = < 0.001). Serum ferritin (11,230.5 v/s 7853.5, p = 0.013) and sIL-2R (32,917.5 v/s 6210, p = < 0.001) were significantly higher in those patients with HLH. sIL-2R correlated very well with HScore (r = 0.98, p < 0.001) compared to ferritin (r = 0.51, p < 0.001) with an AUROC of 1.00 compared to 0.694 (95% CI 0.557–0.831) of serum ferritin for diagnosing HLH. A cut-off value of 10,345 pg/ml for sIL-2R had a sensitivity and specificity of 100% for HLH, whereas, a ferritin value of 8613 ng/ml had only 67% sensitivity and 55% specificity. Conclusion: sIL-2R could be a single most useful biomarker to differentiate dengue fever patients who are likely to progress to HLH, from those that are not. Full workup for HLH could be limited only to those patients with elevated sIL-2R, especially in resource limited settings.