Abstract:
Background: Drug resistance is a challenge for the global control of tuberculosis. We examined
mortality in tuberculosis patients from high-burden countries, according to concordance or
discordance of results from drug susceptibility testing (DST) done locally and in a reference
laboratory.
Methods: We collected Mycobacterium tuberculosis isolates from adult patients in Côte d’Ivoire,
Democratic Republic of the Congo, Kenya, Nigeria, South Africa, Peru, and Thailand, stratified by
HIV status and tuberculosis drug resistance. Molecular or phenotypic drug susceptibility testing
(DST) was done locally and at the Swiss tuberculosis reference laboratory. We examined mortality
during treatment according to DST results and treatment adequacy in logistic regression models
adjusting for sex, age, sputum microscopy and HIV status.
Findings: 634 tuberculosis patients were included; median age was 33.2 years, 239 (37.7%) were
female, 272 (42.9%) HIV-positive and 69 (10.9%) patients died. Based on the reference laboratory
DST, 394 (62.2%) strains were pan-susceptible, 45 (7.1%) mono-resistant, 163 (25.7%) multidrug-
resistant (MDR-TB), and 30 (4.7%) had pre-extensive or extensive drug resistance (pre-XDR/XDR-TB). Results of reference and local laboratories were discordant in 121 (19.1%) cases.
Overall, sensitivity and specificity to detect any resistance were 90.8% and 84.3%, respectively.
Mortality ranged from 6.0% (20/336) in patients with pan-susceptible tuberculosis treated
according to WHO guidelines to 57.1% (8/14) in patients with resistant strains who were under
treated. In logistic regression, compared to concordant DST results, the adjusted odds ratio of
death was 7.33 (95% CI 2.70–19.95) for patients with discordant results potentially leading to
under treatment.
Interpretation: Inaccurate DST by comparison to a reference standard led to under treatment of
drug resistant tuberculosis and increased mortality. Rapid molecular DST of first- and second-line
drugs at diagnosis is required to improve outcomes in patients with MDR-TB and pre-XDR/XDR-
TB.
