We used available small RNA sequencing of blood serum from 398 children with mild-to-moderate persistent asthma from the CAMP. Small RNA-seq libraries were prepared using the Norgen Biotek (Thorond, Canada) Small RNA Library Prep Kit and sequenced on the Illumina (San Diego, CA, USA) NextSeq 500 platform by Norgen Biotek. The exceRpt pipeline was employed for the QC of the RNA-seq data.17 (link) We excluded miRs with mapped read counts < 5 or with coverage < 50% of all subjects from the study. Using the DESeq2 R package,18 (link) we normalized reads by relative log expression, which has been shown to be a robust normalization method.19 (link) The small RNA sequencing was performed in 22 batches, which can introduce technical effects due to inconsistencies during preparation and handling. Guided principal components analysis (gPCA)20 (link) was used to check for batch effects on mapped read counts per sample, which did not detect a significant batch affect after data normalization (P = 0.371, Supplementary Fig. S1).