Table 3.

Summary of findings: methenamine hippurate versus control (placebo or antiseptic iodine perineal wash) for the prevention of UTI^a

Certainty assessment							Patients, n		Effect		Certaintyb
Studies, n	Study design	Risk of bias	Inconsistency	Indirectness	Imprecision	Other considerations	Methenamine hippurate, n (%)	Control, n (%)	Relative RR (95% CI)	Absolute RR (95% CI)
Patients remaining asymptomatic (follow-up: 6–12 months; assessed with number of patients that remained asymptomatic)
2	RCT	Seriousc	Very seriousd	Not serious	Seriouse	Publication bias strongly suspected f	15/39 (38.5)	14/33 (42.4)	1.00 (0.27 to 3.66)	0 fewer per 1000 (from 310 fewer to 1000 more)	Very low
Symptomatic UTI episodes (follow-up: 12 months; assessed with number of symptomatic UTI episodes)
2	RCT	Seriousc	Seriousg	Not serious	Seriouse	Publication bias strongly suspectedf	The pooled results of two RCTs on the number of symptomatic UTI episodes showed a non-statistically significant trend of benefit for methenamine hippurate with a total RR of 0.56 (95% CI = 0.13 to 2.35) with high heterogeneity (I2 93%)				Very low
Any adverse outcomes (follow-up: 12 months; assessed with number of patients with a reported adverse outcome)
2	RCT	Seriousc	Not serious	Not serious	Seriouse	Publication bias strongly suspected f	6/55 (10.9)	2/27 (7.4)	1.32 (0.23 to 7.77)	24 more per 1000 (from 57 fewer to 501 more)	Very low

^a Setting: community, outpatient, and primary care.

^b GRADE Working Group grades of evidence — high: very confident that the true effect lies close to that of the estimate of the effect; moderate: moderately confident in the effect estimate — the true effect is likely to be close to the estimate of the effect but there is a possibllity that it is substantially different; low: confidence in the effect estimate is limited — the true effect may be substantially different from the estimate of the effect; very low: little confidence in the effect estimate — the true effect is likely to be substantially different from the estimate of effect.

^c Allocation concealment and blindind of outcome assessment is unclear.

^d High heterogeneity as each study compared methenamine hippurate against a different control group.

^e Small sample size.

^f Small number of studies hindered assessment of publication bias.

^g High heterogeneity. CI = confidence interval. RCT = randomised controlled trial. RR = risk ratio. UTI = urinary tract infection.