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. 2014 Oct 23;9(10):e107552.
doi: 10.1371/journal.pone.0107552. eCollection 2014.

Diagnosis of tuberculosis by using a nucleic acid amplification test in an urban population with high HIV prevalence in the United States

Miwako Kobayashi  1 , Susan M Ray  1 , John Hanfelt  2 , Yun F Wang  3
Affiliations

Diagnosis of tuberculosis by using a nucleic acid amplification test in an urban population with high HIV prevalence in the United States

Miwako Kobayashi et al. PLoS One. .

Abstract

Background: Use of nucleic acid amplification tests (NAAT) for the diagnosis of Mycobacterium tuberculosis (TB) has been recommended on respiratory specimens submitted for acid-fast bacilli (AFB) testing. It also helps distinguish between TB and non-tuberculous mycobacteria (NTM) species in a setting where NTM rates are relatively high. The purposes of this study are to describe the trend and characteristics of all AFB smear-positive respiratory samples that underwent amplified Mycobacterium tuberculosis direct (MTD) testing, a type of NAAT, and to evaluate the clinical utility and necessity of the test for diagnosis of TB in a population with high-HIV prevalence.

Methods: Prospective diagnostic testing and retrospective data analyses were conducted on all AFB smear-positive respiratory samples that underwent MTD testing from 2001 to 2011 at Grady Memorial Hospital (GMH), Atlanta, USA. The test performance was compared to culture.

Results: A total of 2,240 AFB smear-positive specimens from 1,412 patients were tested and analyzed in the study. The proportion of specimens that were culture-positive for TB was 28.5%. Sensitivity, specificity, positive predictive value, and negative predictive value of the MTD were 99.0%, 98.0%, 95.3% and 99.6%, respectively. A downward trend was observed in the yearly numbers as well as the proportions of MTD-positive specimens during the study period (p<0.01). There were 2,027 (90.5%) specimens from patients with known HIV status, of which 70.6% was HIV positive and the majority of them (81.8%) had CD4 counts of less than 200 cells/µL. HIV-positives were more likely to have NTM compared to HIV negatives (67.7% vs. 35.4%, p<0.01).

Conclusion: Despite the decrease in the incidence of TB, NAAT continues to be an accurate and important diagnostic test in a population with high HIV prevalence, and it differentiates TB and NTM organisms.

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Conflict of interest statement

Competing Interests: Dr. Yun F. Wang and Dr. Susan Ray received funding from CDC and Georgia EIP. Dr. Wang received pilot funding from Emory Global Health Institute, and funding for clinical trials was sponsored by Cepheid and bioMerieux. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Trend in the number of samples submitted for MTD testing, number with positive MTD, and the percent of samples with positive MTD by year, per specimen.
Figure 2
Figure 2. Trend in the number of samples submitted for MTD testing, number with positive MTD, and the percent of samples with positive MTD by year, per unique visit.
See this image and copyright information in PMC

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