Anemia independently predicted tuberculosis among HIV-positive Cape Town patients not taking antiretroviral therapy. Sensitivities of TB diagnostic assays were much higher in people with moderate or severe anemia than in those with mild or no anemia.
Because the relationship between anemia and undiagnosed TB remains poorly understood in sub-Saharan Africa, researchers conducted this study of TB prevalence among antiretroviral-naive Cape Town adults. They classified anemia by World Health Organization criteria. Health workers screened all study participants for TB by testing paired sputum samples by liquid culture, fluorescence microscopy, and Xpert MTB/RIF. They tested urine samples for lipoarabinomannan (LAM) with the Determine TB-LAM diagnostic assay.
Among 485 patients with complete results, 216 (44.5%) had normal hemoglobin, 121 (24.9%) had mild anemia, 123 (25.4%) had moderate anemia, and 25 (5.2%) had severe anemia.
Culture-confirmed pulmonary TB could be diagnosed in in 19 of 216 people without anemia (8.8%), 20 of 121 (16.5%) with mild anemia, 32 of 123 (26.0%) with moderate anemia, and 10 of 25 (40.0%) with severe anemia (P < 0.001). Statistical analysis considering multiple TB risk factors identified anemia as a strong independent predictor of TB.
Diagnostic assay sensitivity was much greater in people with moderate or severe anemia than in those with mild or no anemia: 42.9% versus 15.4% for sputum microscopy, 54.8% versus 0% for urine LAM, 71.4% versus 15.4% for sputum microscopy plus urine LAM, and 73.8% versus 41.0% for sputum Xpert (P < 0.01 for all differences).
“A very high prevalence of undiagnosed TB was found in patients with moderate or severe anemia,” the researchers conclude. “Such patients should be prioritized for routine microbiological investigation using rapid diagnostic assays.”
Source: Andrew D. Kerkhoff, Robin Wood, Monica Vogt, Stephen D. Lawn. Predictive value of anemia for tuberculosis in HIV-infected patients in sub-Saharan Africa: an indication for routine microbiological investigation using new rapid assays. JAIDS. 2014; 66: 33-40.
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Source: IAS