DOI: 10.1097/QAD.0b013e32833c1db1
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PMID: 20588165
Issn Print: 0269-9370
Publication Date: 2010/07/31
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Excerpt
In this issue, Komati et al.[3] add fuel to this fire by describing the impact of historical and incident TB in a prospective cohort of 1771 HIV-infected South Africans initiating antiretroviral therapy (ART). Their major findings indicate that historical TB was associated with increased mortality, likely as a marker for poorer baseline health status, as this association disappeared after adjustment for covariates such as CD4 cell count, body-mass index, and hemoglobin. Incident TB after ART initiation, however, was independently associated with mortality even after adjustment for covariates (hazard ratio 2.49). Most TB events occurred within the first 3 months after ART initiation, 19.88 cases per 100 person-years, compared to 4.11 cases per 100 person-years in those who had been on therapy for more than 24 months. Of note, incident TB occurred more frequently in those with virologic failure after ART initiation (hazard ratio 1.54). Alarmingly, these authors recently reported poor sputum smear sensitivity (33%) for detection of culture-positive TB, and disturbing rates of drug resistance (20.6% with multidrug resistant TB, 3.7% with extensively drug resistant TB) from the same cohort [4].
So long as successful comanagement of HIV–TB coinfection lags behind ART provision, TB will threaten fragile gains in survival resulting from implementation of UNAIDS universal access goals [5]. As is often the case, the problem is not knowing what to do, but rather how best to do it in settings with underresourced and fragmented public health systems.
The first priority must be to diagnose and treat HIV at earlier stages. Since 2007, WHO has advocated ‘opt-out’ provider-initiated HIV testing and counseling to increase testing uptake [6]. It has been proposed that expanding this further to annual, universal testing of a population, followed by immediate provision of ART, could eliminate HIV within 50 years in a theoretical population mirroring South African dynamics [7]. Tremendous debate has ensued about the underlying tensions between individual and public health imperatives to HIV testing and ART initiation, but identifying and treating individuals at earlier stages of HIV infection will clearly diminish individual and population vulnerability to TB. Updated WHO adult treatment guidelines now advocate initiating ART in asymptomatic individuals when CD4 cell count declines below 350 cells/μl rather than 200 cells/μl, the articulated rationale for which includes not insignificantly, achievable reductions in TB transmission and incidence with wider, earlier application of ART [8].
Secondly, donors must direct research funding to develop better, low cost, rapid mechanisms for diagnosing TB and assessing drug resistance among HIV-infected individuals. For instance, the liquid culture microscopic observation drug susceptibility (MODS) assay allows accurate ascertainment of TB status and drug resistance within 21 days of sputum collection in HIV-infected persons, at a cost of 13.62 US dollars per person screened [9]. Accurately diagnosing those without TB is as important as diagnosing those with TB, to identify persons who would benefit from isoniazid preventive therapy, a vastly underutilized intervention in resource-limited settings precisely because active TB is so difficult to exclude.
