Community-based serological screening for Chagas disease in London: a cross-sectional, observational pilot study

Abstract

Introduction: Chagas disease (CD) is increasingly recognised as a public health problem in non-endemic settings. The UK is home to a large Latin American migrant population; yet, there is no formal screening programme for CD.The aim of this study was to co-design and evaluate a community-based screening initiative for CD in Latin American migrants in London, UK.

Methods: This was a cross-sectional, observational pilot study, using questionnaires and point of care tests (POCTs: finger-prick lateral flow assays for qualitative detection of Immunoglobulin G (IgG) to Trypanosoma cruzi). Screening was offered at nine community (non-healthcare setting) events advertised on social media and by word-of-mouth. The main outcome measures were seroprevalence of T. cruzi infection, by age, sex, country of birth and event type, positive predictive value (PPV) of the POCT, linkage to care and screening yield.

Results: 334 adult participants (254 at CD-specific events and 80 at other events) participated in screening between December 2021 and May 2023. All were first-generation or second-generation migrants from South America, Central America or Mexico. 206 (62%) were born in Bolivia and 223 (67%) were women.A total of 79 out of 334 (24%) participants screened positively, of whom 77 (97%) attended for confirmatory laboratory serology and 70 (21% total population screened) were confirmed as true cases (two laboratory-performed serological assays positive). The POCT-PPV overall was 91%. 90% of the true confirmed cases detected through community screening were still engaged in specialist care at a mean of 2.5 years follow-up. The number needed to screen to link one confirmed case into specialist care was 5.3.

Conclusions: Active case finding through delivery of targeted community-based screening using POCTs at either dedicated events or as pop-up testing at other events can effectively identify people with CD, with a high yield and minimal loss to follow-up.

Keywords: Community Health; Epidemiology; Public Health.

Figure 1. Point of care test reading charts developed by the study team. Control (C) and test (T) band strength were visually graded from 0–4 (0=negative, 1=very weak, 2=weak/moderate, 3=moderate/strong, 4=very strong). T1/2/3/4 were all considered reactive tests, requiring laboratory and clinical follow-up.

Figure 2. Flowchart of participant recruitment and study activities. T. cruzi, Trypanosoma cruzi.