Journal Article

Diagnosis of Tuberculosis by Using a Nucleic Acid Amplification Test in an Urban Population with High HIV Prevalence in the United States

Kobayashi, Miwako, Hanfelt, John, Wang, Yun F., Ray, Susan M.

2014

Overview

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. 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. 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). 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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Acids / Adolescent / Adult / Aged / Aged, 80 and over / Air bases / Amplification / Analysis / Bacilli / Biology and Life Sciences / CD4 antigen / CD4 Lymphocyte Count / Cell culture / Cost analysis / Data processing / Demography / Diagnosis / Diagnostic systems / Disease control / Female / HIV / HIV Infections - complications / HIV Infections - epidemiology / HIV Infections - immunology / HIV tests / Hospitals / Human immunodeficiency virus / Humans / Infections / Infectious diseases / Male / Medical diagnosis / Medical laboratories / Medicine / Medicine and Health Sciences / Middle Aged / Mycobacterium tuberculosis / Nucleic Acid Amplification Techniques - methods / Nucleic acids / Patients / Prevalence / Prevalence studies (Epidemiology) / Public health / Smear / Test procedures / Trends / Tuberculosis / Tuberculosis - complications / Tuberculosis - diagnosis / United States - epidemiology / Urban population / Urban Population - statistics & numerical data / Urban populations / Young Adult