Rates of tuberculosis recurrence increased by almost ninefold between episode 2 and 5 regardless of HIV status, according to a study assessing recurrent tuberculosis in Cape Town, South Africa, over a 13-year period.
“[Tuberculosis (TB)] disease among previously treated individuals (recurrent TB) constitutes 5% to 30% of the TB burden, with higher proportions found in high-prevalence settings. Recurrence may be due to endogenous relapse or exogenous reinfection,” Sabine Hermans, MD, PhD, MSc, assistant professor at Amsterdam Institute for Global Health and Development and the University of Amsterdam, and colleagues wrote. “Repeated recurrences in the same individual add to the TB burden, but the extent has not been quantified due to difficulties in identifying recurrence in routinely collected data because of lacking longitudinal patient registration systems.”
Hermans and colleagues determined the rate of recurrent TB per subsequent episode by matching individual treatment episodes in Cape Town which has one of the highest TB burdens worldwide between 2003 and 2016. The researchers then estimated the recurrence rate, stratified according to subsequent TB episode and HIV status, among patients with a first episode of TB who finished treatment successfully, adjusting person-time to background mortality according to age, sex and HIV status.
A total of 292,915 TB episodes among 263,848 individuals were included in the study. Results showed that the rate of recurrent TB was 16.4 per 1,000 person-years (95% CI, 16.2-16.6) and increased per subsequent episode by 8.4-fold, from 14.6 to 122.7 per 1,000 from episode 2 to episode 6, respectively. The researchers observed similar increases when results were stratified according to HIV status. Rates among people living with HIV were higher than those of individuals without HIV for episodes 2 and 3 (2 and 1.5-fold higher, respectively) and the same thereafter.
“We found a high rate of TB disease recurrence increasing per subsequent episode, which was independent of previous treatment outcome and HIV status. These findings suggest the HIV epidemic cannot fully explain the high burden of retreatment TB in Cape Town,” the authors wrote. “Therefore ... high ART coverage will not be sufficient to curb it.”
Instead, Hermans and colleagues say that the burden “is more likely explained” by high transmission rates as well as an increased risk for infection or progression to disease associated with prior TB treatment. They also call for further research into the mechanisms underlying this correlation.
“The very high recurrence rates would justify increased TB surveillance of patients with more than one episode,” the researchers wrote.
Hermans SM, et al. Clin Infect Dis. 2020;doi:10.1093/cid/ciaa470.