Estimating the proportion of relapse following treatment of Visceral Leishmaniasis: meta-analysis using Infectious Diseases Data Observatory (IDDO) systematic review.

Background: Occurrences of relapse after 6-months post-treatment has been reported in recent Visceral Leishmaniasis (VL) efficacy studies. A meta-analysis was carried out to quantify the proportion of relapses observed at and beyond 6-months using the Infectious Diseases Data Observatory (IDDO) systematic review (SR) database.

Methods: Studies in the IDDO SR database (1983-2021; 160 studies) were eligible for inclusion if follow-up was at least 6-months, relapse was clearly reported, and patients with HIV coinfections were excluded. Meta-analysis of single proportion was undertaken and the estimates were reported with 95% confidence intervals (CI).

Findings: Overall, 131 studies enrolling 27,687 patients were included; 1193 patients relapsed. In the Indian sub-continent (ISC), relapse estimates at 6-months was 4.5% [95% CI: 2.6%-7.5%;  = 66.2%] following single dose liposomal amphotericin B (L-AmB) and 1.5% [95% CI: 0.7%-3.3%;  = 0%] for L-AmB in a combination therapy. In East Africa (EA), corresponding estimates were 3.8% [95% CI: 1.3%-10.9%;  = 75.8%] following pentavalent antimony (PA), and 13.0% [95% CI: 4.3%-33.6%;  = 0%] for PA + paromomycin. From 21 studies with follow-up longer than 6-months, 0.6% [95% CI: 0.2%-1.8%;  = 0%] of patients relapsed after 6-months and estimated 27.6% [95% CI: 11.2%-53.4%;  = 12%] of relapses would have been missed by a 6-month follow-up.

Interpretation: The estimated relapse proportion ranged from 0.5% to 4.5% in ISC and 3.8%-13.0% in EA with the currently recommended drugs. Over one-quarter of relapses would be missed with 6-months follow-up suggesting a longer follow-up may be warranted.

Funding: Wellcome Trust (ref: 208378/Z/17/Z).