Antimicrobial prophylaxis for vesicoureteral reflux: which subgroups of children benefit the most?

Background: While the Randomized Intervention for children with Vesicoureteral Reflux (RIVUR) trial found that long-term antimicrobial prophylaxis reduced the risk of urinary tract infection (UTI) recurrences by 50%, 10 children had to be treated with long-term antimicrobial prophylaxis for one to benefit (i.e., observed number needed to treat (NNT) of 10). Accordingly, we re-analyzed RIVUR data to systematically identify subgroups of children with vesicoureteral reflux (VUR) with a smaller NNT. Methods: Using patient-level data from the RIVUR trial, we applied penalized regression methods including the baseline age, VUR, and bowel-bladder dysfunction (BBD) as covariates to identify subgroups that consider the trade-off between absolute risk difference and size. Results: We identified three relevant subgroups of children that appear to benefit from long-term antimicrobial prophylaxis, all with NNTs smaller than the NNT of 10. Children with grade IV VUR and BBD, 1% of the RIVUR sample, had a NNT of 2; children with BBD, 12% of the RIVUR sample, had a NNT of 4; children with BBD (and any grade VUR) or with grade IV VUR (regardless of BBD status), which was the combination of the first two subgroups and included 19% of children in the RIVUR sample, had a NNT of 4. Conclusions: Use of long-term antimicrobial prophylaxis appears to be particularly relevant for children with BBD (and any grade of VUR) or those with grade IV VUR (regardless of BBD status) who were at high risk of UTI recurrences.