A comparative study of IL‐6, CRP and NT‐proBNP levels in post‐COVID multisystem inflammatory syndrome in children (MISC) and Kawasaki disease patients

Background Post‐COVID multisystem hyperinflammatory syndrome in children (MISC) has clinical and laboratory similarities with Kawasaki disease (KD). Inflammatory markers like C‐reactive protein (CRP), interleukin 6 (IL6) as well as N‐terminal probrain natriuretic peptide (NT‐proBNP) are elevated in both. This study attempts a comparative analysis of the 3 markers in an attempt at early differentiation for planning appropriate management. Methodology This analytical study conducted at the Institute of Child Health, Kolkata, India compared the levels of the above 3 markers at admission between 72 patients with KD, 30% of whom had coronary artery lesions (CALs) collected over a period of 18 months (Jan 2017‐June 2018), with 71 MISC patients over a period of 6 months (July 2020‐December 2020). The non‐parametric Mann‐Whitney U test was used to test for similarity in distributions of the samples of CRP, NT‐proBNP and IL6 in KD and MISC patients using correction factor for similar ranks. The 3 parameters were compared using receiver operating characteristic (ROC) curve analysis. Results Mean IL6 value in KD was 83.22 pg/mL and in MISC 199.91 pg/mL, which was not found to be statistically significant ( P  = .322 > .05).However mean NT‐proBNP (914.91 pg/mL) with CRP level (96.32 mg/L) in KD was significantly lower ( P  < .05 for both cases) than that in MISC (9141.16 pg/mL and 145.66 mg/L respectively). ROC analysis showed NT‐proBNP has the best sensitivity and specificity in predicting MISC. Conclusion NT‐proBNP and CRP are significantly higher among MISC patients; ROC analysis shows levels >935.7 pg/mL and >99.55 mg/L respectively might act as a guide to differentiate between them.