Disseminated Mycobacterium avium complex infection as a differential diagnosis of tuberculosis in HIV patients

BACKGROUND: Disseminated Mycobacterium avium complex infection (DMAC) has symptoms and microscopic findings similar to those of TB in HIV patients. To inform a clinical algorithm-based differential diagnosis, we aimed to characterise the clinical features of DMAC.METHODS: This was a retrospective cohort study of 192 HIV-positive patients with culture-confirmed mycobacterial infections hospitalised during 1996-2016 at a major HIV/AIDS treatment centre in Taiwan.RESULTS: HIV patients with DMAC (n = 58) had a three times higher 1-year mortality than those with TB (n = 98) (48.3% vs. 16.3%, P < 0.001). DMAC and TB were not distinguishable by the WHO TB screening criteria (fever, cough, night sweats or weight loss). Nevertheless, DMAC was characterised by a lower median CD4 count (5.0 cells/µL vs. 38.5 cells/µL, P < 0.001), lower median body mass index (BMI) (17.7 kg/m² vs. 19.7 kg/m², P = 0.002) and the absence of chest radiographic findings (P < 0.001). Simultaneous presence of CD4 <20 cells/µl, BMI <18.5 kg/m² and negative chest radiographic finding had a 98% specificity for diagnosing DMAC against TB or other types of mycobacterial infections.CONCLUSION: DMAC is an important differential diagnosis of TB in HIV patients. A simple rule based on CD4, BMI and chest radiography may inform the decision to start anti-DMAC treatment in patients with mycobacterial infection.