Nine studies with 1,054 patients in 10 treatment arms were included. Five of these were RCTs (n=576) that compared concomitant (n=293) and triple therapy (n=283). The four other non-randomized studies evaluated concomitant therapy in 478 patients. Two trials were single-blinded; all others were unblinded and open-label.
Pooled estimates of the five RCTs showed superiority of concomitant therapy over triple therapy for Helicobacter pylori infection, with an intention-to-treat pooled odds ratio of 2.86 (95% CI 1.73 to 4.73). There was no significant heterogeneity between trials. The pooled eradication rate with concomitant therapy based on the intention-to-treat analysis in 695 of 771 patients over all 10 treatment arms was 89.7% (95% CI 86.8 to 92.1%).
Anaphylaxis to medication was reported in three patients in three studies. No other severe side-effects were reported. Mild to moderate side-effects were reported in 27% to 51% of patients treated with the concomitant quadruple therapy versus 21% to 48% of patients treated with triple therapy.
Univariate meta-regression analysis of the five RCTs did not identify any variables that could explain outcome variation. However, analyses of the 10 treatment arms showed that age and treatment duration were significant variables that might explain variation of eradication rates.
There was evidence of possible publication bias for the per protocol analysis of eradication rates, but not for other analyses in this review.