Prevalence of Tuberculosis, HIV and Respiratory Symptoms in Two Zambian Communities: Implications for Tuberculosis Control in the Era of HIV

Abstract

BackgroundThe Stop TB Partnership target for tuberculosis is to have reduced the prevalence of tuberculosis by 50% comparing 2015 to 1990. This target is challenging as few prevalence surveys have been conducted, especially in high burden tuberculosis and HIV countries. Current tuberculosis control strategies in high HIV prevalent settings are therefore based on limited epidemiological evidence and more evidence is needed from community-based surveys to inform improved policy formulation.Methods and Findings8044 adults were sampled from 2 sub-districts (wards) in Lusaka province, Zambia. Questionnaires were used to screen for symptoms, respiratory samples were obtained for culture and oral secretions collected for HIV testing. 79 individuals were found to have Mycobacterium tuberculosis in their sputum, giving an adjusted overall prevalence of tuberculosis of 870/100,000 (95% CI 570–1160/100,000). The adjusted overall prevalence of HIV was 28.61% (95% CI 26.04–31.19). HIV- infection was significantly associated with prevalent tuberculosis (Adj OR 2.3, 95% CI 1.42–3.74) and the population attributable fraction of HIV for prevalent tuberculosis was 36%. Symptoms such as prolonged cough (adj OR 12.72, 95% CI 7.05–22.94) and fever (Adj OR 2.04, 95%CI 1.23–3.39), were associated with prevalent tuberculosis, but 8 (10%) individuals with prevalent tuberculosis denied having any symptoms at all and only 34 (43%) would have been classified as a TB suspect by current guidelines.ConclusionsUndiagnosed tuberculosis is a challenge for tuberculosis control and new approaches are needed if we are to reach international targets. Epidemiological studies can inform screening algorithms for both detection and prevention of active tuberculosis.

Understanding the incremental value of novel diagnostic tests for tuberculosis

“…Specifically, in any given setting, TB transmission may occur primarily from people who are not sufficiently ill to seek care 49,50 ; those who are seeking care, but have symptoms (for example, a mild cough) not specific to TB 51 ; or those with severe or prolonged symptoms, but who test negative for TB and are therefore not treated (Fig. 1b).…”

The HIV-associated tuberculosis epidemic—when will we act?

“…[44][45][46][47][48] HIV-positive individuals had 1·7-4·4 times higher prevalence of culture-positive tuberculosis and 0·8-3·5 times higher prevalence of undiagnosed smearpositive tuberculosis than did HIV-negative individuals: 0-34% of the total burden of smear-positive disease was directly attributable to HIV. [44][45][46][47][48] Most of these patients reported no previous contact with health services, which is consistent with long-term infectiousness before presentation at health facilities.…”

“…[44][45][46][47][48] HIV-positive individuals had 1·7-4·4 times higher prevalence of culture-positive tuberculosis and 0·8-3·5 times higher prevalence of undiagnosed smearpositive tuberculosis than did HIV-negative individuals: 0-34% of the total burden of smear-positive disease was directly attributable to HIV. [44][45][46][47][48] Most of these patients reported no previous contact with health services, which is consistent with long-term infectiousness before presentation at health facilities. 14 Findings from two studies in Zimbabwe showed that in populations with high prevalence of HIV, provision of easy access to tuberculosis diagnosis in occupational clinics 44 or in outreach facilities 49 can substantially reduce undiagnosed tuberculosis (to 0·3% and 0·4% culture-positive disease, and to 0·1% and 0·2% smear-positive disease, respectively).…”

“…46,[52][53][54][55][56] Unfortunately, screening by culture is not feasible in most resource-poor settings, and the only practical approaches are screening for symptoms and by sputum smear microscopy, neither of which is ideal. Less than a third of culture-positive patients will be smear positive, and the overlap between symptoms of tuberculosis and HIV results in low specifi city of symptom-based enquiries.…”

“…Less than a third of culture-positive patients will be smear positive, and the overlap between symptoms of tuberculosis and HIV results in low specifi city of symptom-based enquiries. 46,[52][53][54][55][56] The most consistently discriminating questions concern cough of any duration, weight loss, fever, and night sweats. Sensitivity is challenging since long-term cough is reported by only 35-65% of culture-positive patients, and up to 21% deny any tuberculosis symptoms at all.…”