Abstract
There are scarce data regarding the value of molecular tests, when used in parallel with classical tools, for the diagnosis of tuberculosis (TB) under field conditions, especially in regions with a high burden of TB-human immunodeficiency virus (HIV) co-infection. We evaluated the usefulness of the polymerase chain reaction dot-blot assay (PCR) used in parallel with Ziehl-Neelsen staining (ZN) for pulmonary tuberculosis (PTB) diagnosis, in a TB-HIV reference hospital. All sputum samples from 277 patients were tested by ZN, culture, and PCR. Performances were assessed individually, in parallel, for HIV status, history of anti-TB treatment, and in different simulated TB prevalence rates. Overall, the PTB prevalence was 46% (128/277); in HIV-seropositive (HIV+) individuals, PTB prevalence was 54% (40/74); the ZN technique had a lower sensitivity (SE) in the HIV+ group than in the HIV-seronegative (HIV−) group (43% vs. 68%; Fisher test, P<0.05); and the SE of PCR was not affected by HIV status (Fisher test; P=0.46). ZN, in parallel with PCR, presented the following results: i) among all PTB suspects, SE of 90%, specificity (SP) of 84%, likelihood ratio (LR)+ of 5.65 and LR− of 0.12; ii) in HIV− subjects: SE of 92%, LR− of 0.10; iii) in not previously treated cases: SE of 90%, LR− of 0.11; iv) in TB, prevalence rates of 5–20%; negative predictive values (NPV) of 98–99%. ZN used in parallel with PCR showed an improvement in SE, LR−, and NPV, and may offer a novel approach in ruling out PTB cases, especially in not previously treated HIV− individuals, attended in hospitals in developing nations.
Highlights
Biológicas - Bioquímica, Universidade Federal do Rio Grande do Sul -UFRGS, Tuberculosis (TB) is one of the most import- Conflict of interest: the authors report no conant health problems in the world, with 1.8 mil- flicts of interest
In Brazil, Ziehl-Neelsen staining (ZN) is the recommended method both for TB diagnosis and treatment control, and sputum culture in solid medium is only indicated in pulmonary tuberculosis (PTB)-suspect cases, such as those with: i) ZN-negative results; ii) paucibacillary and extrapulmonary specimens; iii) therapeutic failure with suspicion of drug resistance; and iv) individuals infected by human N immunodeficiency virus (HIV).[3]
In order to compare the performance of the use of a molecular test (PCR dot-blot assay) or culture in parallel with ZN for the diagnosis of PTB, we conducted a prospective study in a TBHIV reference hospital, located in Porto Alegre City in the south of Brazil where, in 2004, 1432 TB cases were reported, 420 of them diagnosed in hospitals and 51% being HIV-infected patients.[8]
Summary
©Copyright L.C. Scherer et al, 2011 Licensee PAGEPress, Italy Infectious Disease Reports 2011; 3:e3 doi:10.4081/idr.2011.e3 of TB, has been considered a novel approach.[5,6,7] In order to compare the performance of the use of a molecular test (PCR dot-blot assay) or culture in parallel with ZN for the diagnosis of PTB, we conducted a prospective study in a TBHIV reference hospital, located in Porto Alegre City in the south of Brazil where, in 2004, 1432 TB cases were reported, 420 of them diagnosed in hospitals and 51% being HIV-infected patients.[8]
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