Contact investigation for tuberculosis: a systematic review and meta-analysis

Abstract

Investigation of contacts of patients with tuberculosis (TB) is a priority for TB control in high-income countries, and is increasingly being considered in resource-limited settings. This review was commissioned for a World Health Organization Expert Panel to develop global contact investigation guidelines.We performed a systematic review and meta-analysis of all studies reporting the prevalence of TB and latent TB infection, and the annual incidence of TB among contacts of patients with TB.After screening 9,555 titles, we included 203 published studies. In 95 studies from low- and middle-income settings, the prevalence of active TB in all contacts was 3.1% (95% CI 2.2–4.4%, I2=99.4%), microbiologically proven TB was 1.2% (95% CI 0.9–1.8%, I2=95.9%), and latent TB infection was 51.5% (95% CI 47.1–55.8%, I2=98.9%). The prevalence of TB among household contacts was 3.1% (95% CI 2.1–4.5%, I2=98.8%) and among contacts of patients with multidrug-resistant or extensively drug-resistant TB was 3.4% (95% CI 0.8–12.6%, I2=95.7%). Incidence was greatest in the first year after exposure. In 108 studies from high-income settings, the prevalence of TB among contacts was 1.4% (95% CI 1.1–1.8%, I2=98.7%), and the prevalence of latent infection was 28.1% (95% CI 24.2–32.4%, I2=99.5%). There was substantial heterogeneity among published studies.Contacts of TB patients are a high-risk group for developing TB, particularly within the first year. Children <5 yrs of age and people living with HIV are particularly at risk. Policy recommendations must consider evidence of the cost-effectiveness of various contact tracing strategies, and also incorporate complementary strategies to enhance case finding.

Commentary: A targets framework: Dismantling the invisibility trap for children with drug-resistant tuberculosis

“…For this proportion, we use the pooled TB disease risk estimated in the two age groups of child contacts in the 2013 systematic review and meta-analysis of TB contact investigations, namely, 10.0 per cent in those less than 5 years old and 8.4 per cent in those 5-14 years old. 63 The disease risk among close contacts of individuals sick with any type of TB that is synthesized in that meta-analysis is consistent with observations in DR-TB household contact investigations. 64,68,98,99 We then multiply the disease risk in each group by the number of child contacts.…”

“…[59][60][61] Adult and pediatric household contacts are at high risk for both infection and disease. 62,63 This is similarly true for those living with someone sick with DR-TB. 64 Recent global guidelines emphasize contact tracing in all households of those sick with TB, 65 particularly households where someone is sick with MDR-TB.…”

Drop-out from the tuberculosis contact investigation cascade in a routine public health setting in urban Uganda: A prospective, multi-center study

“…We constructed a cascade for household contact investigation to describe the proportions of: 1) index patient households recruited; 2) index patient households visited; 3) contacts screened for TB; and 4) contacts completing evaluation for, and diagnosed with, active TB.…”

“…Specifically, there are few details about when and where participants are lost-to-follow-up, essential information for designing interventions to improve delivery of contact investigation. [3][4][5] Cascade analysis, frequently applied to understand cumulative losses along the HIV care continuum [6,7], can clarify the most important gaps in delivery of TB evaluation and care, and in so doing inform the design and targeting of interventions. [8] Identifying TB patients via household contact investigation depends on effectively completing four key steps in the delivery cascade: 1) scheduling visits to homes of index TB patients; 2) initiating these visits by physically reaching the homes of index patients; 3) screening all household contacts; and 4) ensuring that all symptomatic and high-risk contacts complete TB evaluation.…”

Uptake of home-initiated tuberculosis evaluation during household contact investigation in Kampala, Uganda: A mixed-methods study

“…[1][2][3][4][5] One important tool for active case-finding is household contact investigation. 6 However, case-finding through contact investigation depends on contacts' ability and willingness not only to complete screening for TB symptoms and risk factors, but also to complete TB evaluation if referred. In a previous study of contact investigation and clinical follow-up for household contacts of pulmonary TB patients, we showed that only 20% of symptomatic or high-risk contacts referred for TB evaluation eventually completed evaluation.…”