Performance of the Roche cobas MTB Assay for the Molecular Diagnosis of Pulmonary Tuberculosis in a High HIV Burden Setting

Increased access to and improved sensitivities of methods for diagnosing Mycobacterium tuberculosis infection and detecting rifampicin and isoniazid resistance are needed. Herein, the performance of the new cobas MTB assay for use on cobas 6800/8800 Systems (Roche) was assessed and compared with two other commercial assays: RealTime MTB (Abbott), and Xpert MTB/RIF (Cepheid). Molecular PCR-based assays were conducted on sputum specimens from individuals with presumptive and confirmed tuberculosis (n = 294) from two clinical facilities in South Africa between December 2016 and October 2017. Liquid mycobacterial culture was the reference. Test sensitivities were 94.7% (95% CI, 88%-98%), 92.6% (95% CI, 85%-97%), and 91.6% (95% CI, 84%-96%) for cobas MTB, RealTime MTB, and Xpert MTB/RIF assays, respectively. cobas MTB sensitivity was unaffected by HIV coinfection (95.7%; 95% CI, 88%-99%; n = 176) and sediment testing (94.7%; 95% CI, 88%-98%). Sensitivities were 81.8% (95% CI, 60%-95%), 72.7% (95% CI, 50%-89%), and 72.7% (95% CI, 50%-89%) among smear-negative, culture-positive individuals (n = 221) for cobas MTB, RealTime MTB, and Xpert MTB/RIF assays, respectively. cobas MTB specificity was 95.7% (95% CI, 89%-99%) and 99% (95% CI, 94%-100%) among HIV coinfected and uninfected individuals, respectively. The cobas 6800/8800 system is already implemented in South Africa for high-throughput HIV viral load testing, making it suitable for integrated HIV/tuberculosis diagnostics.

Indoor air pollution from secondhand tobacco smoke, solid fuels, and kerosene in homes with active tuberculosis disease in South Africa

Objectives

Secondhand tobacco smoke (SHS), use of solid fuels, and kerosene may play an important role in perpetuating the tuberculosis (TB) epidemic. The purpose of this study was to explore the prevalence of household air pollution (HAP) from these sources in homes of someone with TB in a high HIV-prevalence setting. A convenience sample of homes and household members participating in an ongoing active case-finding study in Matlosana district townships surrounding Klerksdorp, South Africa were included.

Results

We found a high prevalence of air pollution from SHS, solid fuels, and kerosene among individuals in homes with a case of prevalent active TB disease in Klerksdorp, South Africa. Adults in 40% of homes reported a daily smoker in the home, and 70% of homes had detectable air nicotine. In homes with a history of previous TB (prior to but not including the index case) as compared to those without previous TB, both SHS (83% vs. 65%, respectively) and solid/kerosene fuel use for more than 1 h/day (27% vs. 21%, respectively) were more prevalent. Larger studies are needed to estimate the risk of TB from these types of air pollution in HIV infected individuals and settings with high HIV prevalence.

Latent tuberculous infection in schoolchildren and contact tracing in Matlosana, North West Province, South Africa

This is a cross-sectional study to estimate the prevalence of latent tuberculous infection (LTBI) and the annual risk of tuberculous infection (ARTI) among a sample of children aged 5 and 7 years in Matlosana, South Africa. LTBI prevalence was significantly higher in children aged 7 years (n = 704) (19.7%, 95%CI 16.75-22.65) than in those aged 5 years (212/1401, 15.1%, 95%CI 13.23-16.97) (P = 0.0075). The ARI was 2.9% (95%CI 2.2-3.6).

Incidence of TB and HIV in prospectively followed household contacts of TB index patients in South Africa

Objective

To report the incidence rates of TB and HIV in household contacts of index patients diagnosed with TB.

Design

A prospective cohort study in the Matlosana sub-district of North West Province, South Africa.

Methods

Contacts of index TB patients received TB and HIV testing after counseling at their first household visit and were then followed up a year later, in 2010. TB or HIV diagnoses that occurred during the period were determined.

Results

For 2,377 household contacts, the overall observed TB incidence rate was 1.3 per 100 person years (95% CI 0.9–1.9/100py) and TB incidence for individuals who were HIV-infected and HIV seronegative at baseline was 5.4/100py (95% CI 2.9–9.0/100py) and 0.7/100py (95% CI 0.3–1.4/100py), respectively. The overall HIV incidence rate was 2.2/100py (95% CI 1.3–8.4/100py).

Conclusions

In the year following a household case finding visit when household contacts were tested for TB and HIV, the incidence rate of both active TB and HIV infection was found to be extremely high. Clearly, implementing proven strategies to prevent HIV acquisition and preventing TB transmission and progression to disease remains a priority in settings such as South Africa.

High prevalence of pulmonary tuberculosis but low sensitivity of symptom screening among HIV-infected pregnant women in South Africa

Symptom screening is a recommended component of intensified case-finding (ICF) for pulmonary tuberculosis (TB) among HIV-infected individuals. Symptomatic individuals are further investigated to either exclude or diagnose pulmonary TB, thus reducing the number of individuals requiring costly laboratory investigation. Those with laboratory evaluations negative for pulmonary TB or who lack symptoms may be eligible for antiretroviral therapy (ART) and/or TB isoniazid preventive therapy (IPT). A four-part symptom screen has been recommended by the World Health Organization (WHO) for identifying TB suspects and those unlikely to have TB. A meta-analysis of studies among HIV-infected individuals calculated a sensitivity of 90.1% for the four-part symptoms screen - of any of cough, fever, night sweats, or weight loss - among patients in clinical care, making it an effective tool for identifying most patients with TB. An important population for intensified case-finding not included in that meta-analysis was HIV-infected pregnant women. We undertook a cross-sectional survey among HIV-infected pregnant women receiving prenatal care at community clinics in South Africa. We obtained a four-symptom review and sputum smear microscopy and mycobacterial culture on all participants. Among 1415 women, 226 (16%) had a positive symptom screen, and 35 (2.5%) were newly diagnosed with culture-positive TB. Twelve were on TB treatment at the time of screening, yielding 47 (3.3%) women with prevalent TB. Symptom screening among women without known TB had a sensitivity of 28% and specificity of 84%. The poor performance of symptom screening to identify women with TB suggests that other approaches may be needed for intensified case-finding to be effective for this population.