Abstract
BackgroundChest-x-ray is routinely used in the diagnosis of smear negative tuberculosis (TB). This study assesses the incremental cost per true positive test of a point-of-care digital chest-x-ray, in the diagnosis of pulmonary mycobacterial infections among HIV patients with presumed tuberculosis undetected by smear microscopy.MethodsConsecutive patients with clinical suspicion of pulmonary tuberculosis were serially tested for Human immunodeficiency virus (HIV), their sputum examined for Acid Fast Bacilli then cultured in broth and solid media. Cultures characterized as tuberculous (M.tb) and non-tuberculous (NTM) mycobacteria by Hain assays were used as gold standards. A chest-x-ray was classified as: (1) consistent for TB, (2) not consistent for TB and (3) no pathology.ResultsOf the 1391 suspected cases enrolled, complete data were available for 952 (68%): 753/952 (79%) had negative smear tests while 150/753 (20%) had cultures positive for TB. Of those, 82/150 (55%) had chest-x-ray signs consistent with TB and 29/82 (35%) were positive for HIV. Within the co-infected, 9/29 (31%) had NTM infections. Among all suspects, the cost per positive case detected using smear microscopy test was $52.84; the overall incremental cost per positive case using chest-x-ray in smear negatives was $23.42, and in smear negative, HIV positive patients the cost was $15.77.ConclusionPoint-of-care chest-x-ray is a cost-effective diagnostic tool for smear negative HIV positive patients with pulmonary mycobacterial infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0675-0) contains supplementary material, which is available to authorized users.
Highlights
Chest-x-ray is routinely used in the diagnosis of smear negative tuberculosis (TB)
Since stationary radiographic units are only available in select hospitals, the vast majority of remotely located directly observed therapy (DOT) clinics rely on routine smear microscopy for the diagnosis and treatment of TB
Given that non-tuberculous mycobacteria (NTM) tend to test negative for acid fast bacilli (AFB) on smear microscopy [2], and the strong association between Human immunodeficiency virus (HIV) coinfection and negative AFB on smear microscopy [3,4,5], routine digital chest-x-ray may be a valuable tool for intensified detection of pulmonary TB and NTM diseases in HIV cases in settings where routine smear microscopy remains the standard of care for TB diagnosis
Summary
Chest-x-ray is routinely used in the diagnosis of smear negative tuberculosis (TB). This study assesses the incremental cost per true positive test of a point-of-care digital chest-x-ray, in the diagnosis of pulmonary mycobacterial infections among HIV patients with presumed tuberculosis undetected by smear microscopy. Given that non-tuberculous mycobacteria (NTM) tend to test negative for acid fast bacilli (AFB) on smear microscopy [2], and the strong association between HIV coinfection and negative AFB on smear microscopy [3,4,5], routine digital chest-x-ray may be a valuable tool for intensified detection of pulmonary TB and NTM diseases in HIV cases in settings where routine smear microscopy remains the standard of care for TB diagnosis In these settings, HIV infected cases with clinical suspicion of smear-negative TB are routinely treated for the disease based on good radiographic signs. Chest-x-ray is the readily available tool for diagnosis of TB in smear-negative cases in these settings [6,7,8]
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