TB prevalence high in MDR-TB household contacts

A high number of household contacts (HHCs) of adults with multi-drug-resistant tuberculosis (MDR-TB) will develop the infection, according to the PHOENIx Feasibility study presented at CROI 2020.

“Over two-thirds of HHCs aged ≥15 years of adult pulmonary MDR-TB cases had evidence of TB infection [as determined by interferon-gamma release assays (IGRA)],” said study author Dr Soyeon Kim from Frontier Science Foundation in Brookline, Massachusetts, US.

The study was conducted at 16 sites in eight countries with high TB burden. The study population comprised 276 index cases (adults with pulmonary MDR-TB who initiated treatment within the past 6 months [median 9 weeks]; median age 35.5 years, 41 percent female) and 686 of their household contacts aged ≥15 years (median age 35 years, 64 percent female). Thirty-six and eight percent of the index cases and HHCs, respectively, were HIV-infected.

Overall, 68.8 percent of HHCs had TB infection. This varied across age groups with TB infection detected in 58.0 percent of the 184 HHCs aged 15–24 years, 75.6 percent of the 334 HHCs aged 25–49 years, and 67.2 percent of the 168 HHCs aged ≥50 years. [CROI 2020, abstract 139]

Multivariable analysis revealed factors associated with TB prevalence in HHCs including age (odds ratio [OR], 1.5 and OR, 0.7 in individuals aged 25–49 and 15–24 years, respectively vs ≥50 years; p<0.001), previous TB treatment (OR, 1.9; p=0.049), history of incarceration or substance or alcohol use (OR, 7.3 vs none; p<0.001), presence of smoker in the household (OR, 1.6; p=0.029), and low quality home primary exterior wall material (eg, adobe, rammed earth, sticks, stones, mud, wood, etc; OR, 1.8 vs brick, cinderblock, stone with mortar; p=0.008).

Sleeping proximity with the index case was also associated with a higher prevalence (same room: OR, 2.4; p=0.04; different room 6–7 and 3–5 nights/week: OR, 2.1 and 1.8, respectively).

There was no association between sex and increased TB infection prevalence in HHCs. A higher prevalence was noted in HHCs with COPD or asthma history, and in those whose fathers were the index cases though these were not statistically significant.

Repeat IGRA testing of 177 HCCs 1 year later showed that 25.5 percent who tested negative or with indeterminate status at previous assessment developed TB infection.

The study also revealed that the use of TB preventive therapy was uncommon. Regardless of age, only 5 percent of high-risk HCCs eligible for TB preventive treatment received it (eg, 26 percent aged <5 years and 13 percent with HIV).

“The high prevalence and continued incidence of TB infection in HHCs of MDR-TB patients suggests that household contact investigation may be critical to global TB control efforts,” said Kim.