Hyperferritinemia in pediatric scrub typhus: A prospective observational study

Background: Hyperferritinemia is increasingly associated with mortality in sepsis. Studies estimating the prevalence of hyperferritinemia in pediatric scrub typhus is limited.Methods: We conducted a prospective observational study from a tertiary care teaching hospital in North India where 72 children with confirmed scrub typhus;17(24%)-PCR positive, 68(94%)-IgM ELISA positive and 13(18%)-both PCR and ELISA positive. Serum ferritin was measured in 62 children to identify the prevalence of hyperferritinemia and determine its association with mortality. Results: Hyperferritinemia (>500µg/L) was seen in 72.6% [n=45] children; 26(42%) were mild (500-2000µg/L), 13(21%) were moderate (2000-10000µg/L) and 6(9.7%) were severe (>10000µg/L). A biphasic pattern of hyperferritinemia was seen with two peaks when plotted against duration since symptoms onset; one between 2 and 3 days (early onset hyperferritinemia) and second peak between 12 and14 days (late onset hyperferritinemia). Early onset hyperferritinemia had more survivors than late onset hyperferritinemia. Non survivors had significantly higher PRISM III, PELOD-2, hyperlactatemia, hypoalbuminemia, organ dysfunction, need for mechanical ventilation and need of RRT. Ferritin had poor sensitivity and specificity in predicting survival with AUC of 0.56. Organ dysfunction and risk scores as PRISM III, PELOD 2 and VIS at admission were better predictors with AUC(95%CI) of 0.72(0.56,0.89), 0.77(0.63,0.92) and 0.90(0.78,1.0) respectively.Conclusions: Hyperferritinemia is common in scrub typhus. A distinct biphasic response was observed with worse outcome in late onset hyperferritinemia. Organ dysfunction and risk scores were better predictors of mortality than ferritin.