Hemophagocytic Lymphohistiocytosis (HLH) is a severe and rapidly progressive immune disorder that can be life threatening if not diagnosed and treated promptly. The HLH2004 guidelines, originally devised for the diagnosis of HLH in pediatric subjects, lack due utility in the adult population. Despite the development of the H-score and adapted HLH 2004 criteria, a critical gap remains in their validation and optimization for diverse populations, including the Indian adult population.

In this prospective observational study, clinical data of 120 patients with suspected HLH were collected. The utility of the H-score and the adapted HLH 2004 for the diagnosis of HLH in adults was studied with respect to expert consensus. The best cut-off value of the calculated H-score for the diagnosis of HLH in our set up was studied using Receiver Operating Characteristic (ROC) curve analysis.

Of 120 adult inpatients suspected of having HLH, 66 were diagnosed with HLH, 37 did not have HLH, and 17 had undetermined status based on expert consensus. Infections were the most common underlying cause, present in 60% of the cases, followed by malignancies (15%). The adapted HLH 2004 criteria demonstrated higher sensitivity (90.9%) but lower specificity (86.5%) compared to the H-Score at the standard cut-off of 169, which had a sensitivity of 81.82% and specificity of 94.59%. ROC curve analysis identified an optimal H-score cut-off of 145, improving the sensitivity to 92.4% and specificity to 89.2%.

Our study highlights the importance of region-specific diagnostic criteria for HLH in adults, particularly in settings where infection is prevalent. By optimizing the H-score cut-off to 145, we improved the diagnostic sensitivity and specificity in our cohort. These findings support the need for tailored diagnostic tools to enhance HLH detection in diverse populations.