The most serious manifestation of rheumatic fever is carditis, as it can lead to chronic rheumatic heart disease. Neutrophil-to-lymphocyte ratio, platelet-to lymphocyte ratio and mean platelet volume have been accepted as novel indicators of the continuing inflammation that is correlated with the severity of valvular involvement in patients with rheumatic carditis.

As a diagnostic study to investigate the correlation of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume with the severity of carditis in children with rheumatic fever.

This was a cross-sectional study at Sanglah Hospital, Bali. Data were collected retrospectively from medical records. Severity of carditis was characterised by a clinical, audible murmur during physical examination and demonstration of valvular involvement by echocardiography. Neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume were calculated from complete blood count. The correlation between parameters was assessed using Spearman’s correlation tests.

From January 2018 to December 2020, we found 45 cases admitted to Sanglah Hospital. Carditis was present in 40 (88.9%) subjects. Neutrophil-to-lymphocyte ratio had a strong positive correlation with severity of carditis (r = 0.66, p = 0.001), while platelet-to-lymphocyte ratio had a weak positive correlation with the severity of carditis (r = 0.23, p = 0.13) and mean platelet volume had a very weak negative correlation with the severity of carditis (r = −0.01, p = 0.95). Using a cut-off of 3.4, neutrophil-to-lymphocyte ratio predicted severe carditis with a sensitivity of 81.8% and specificity of 91.3%.

There was a positive correlation between neutrophil-to-lymphocyte ratio and severity of carditis in children with rheumatic fever. Neutrophil-to-lymphocyte ratio might be used as a diagnostic tool to predict the diagnosis of carditis severity.