Differentiating abdominal pain due to COVID-19 associated multisystem inflammatory syndrome from children with acute appendicitis: a score system

PURPOSE: Differentiating abdominal pain due to coronavirus disease (COVID-19)-associated multisystem inflammatory syndrome (MIS-C) in children with acute appendicitis (AA) can cause diagnostic dilemmas. This study aimed to evaluate the efficacy of a previously described scoring system and improve its diagnostic ability in differentiating between these diseases. METHODS: This study was conducted between March 2020 and January 2022. Patients who had MIS-C with gastrointestinal system (GIS) involvement and patients who underwent surgery for appendicitis were included. First, all patients were evaluated using the new scoring system (NSS). The groups were compared by adding new MISC-specific parameters to NSS. The scoring system was evaluated using propensity score matching (PSM). RESULTS: A total of 35 patients with abdominal pain due to GIS involvement in MIS-C (group A) and 37 patients with AA who had ALT, PRC, and D-dimer results at their first admission (group B) were included in the study. The mean age of patients in group A was lower than that of patients in group B (p < 0.001). False NSS positivity was found in 45.7% of the patients with MIS-C. Lymphocyte (p = 0.021) and platelet counts (p = 0.036) were significantly lower in the blood count and serum D-dimer (p = 0.034), C-reactive protein (CRP) (p < 0.001), and procalcitonin (p < 0.001) were significantly higher in the MIS-C group. We created a scoring system called the Appendicitis–MISC Score (AMS) using the NSS and new parameters. The sensitivity and specificity of AMS diagnostic scores were 91.9% and 80%, respectively. CONCLUSION: MIS-C with GIS involvement may present as acute abdomen. It is difficult to differentiate this condition from acute appendicitis. AMS has been shown to be useful for this differentiation.