Economic evaluation of the use of PCR assay in diagnosing pulmonary TB in a low-incidence area.

To determine whether polymerase chain reaction (PCR) testing in the initial diagnosis of pulmonary tuberculosis (TB) is cost-effective in a low-prevalence population, an economic evaluation was carried out between the smear and culture (NOPCR) and smear, culture and PCR (+PCR) strategies. A decision tree model based on retrospective laboratory data was developed to assess the strategies of testing patients with suspicion of TB. Direct healthcare costs prior to confirmation of TB or nontuberculous mycobacteria by PCR or culture were included. Effectiveness was measured by the probability of correct treatment and isolation decisions. In the baseline situation NOPCR costs Euro 29.50 less than the +PCR strategy per patient tested. According to sensitivity analyses, reducing PCR test price, shortening test performance time or increasing the proportion of smear-positive patients in the tested population would contribute to cost savings with the +PCR strategy. Routine polymerase chain reaction testing of all specimens from suspected tuberculosis patients in a low-prevalence population was not cost-saving. When the polymerase chain reaction assay was applied only to smear-positive sputum specimens, the smear and culture strategy was clearly dominated by it, i.e. the polymerase chain reaction smear-positive sputum strategy was less costly and more effective in producing correct treatment decisions and isolations.

Mycobacterium tuberculosis complex is not detected by DNA amplification assay in sputum specimens of patients with lung scars due to past pulmonary tuberculosis.

OBJECTIVE: To evaluate detection of false-positive sputum amplification assay results in former tuberculosis patients with residual pulmonary scars. DESIGN: A total of 268 sputum specimens from 25 war veterans with tuberculosis during 1940-1959, without adequate chemotherapy, and 19 subjects effectively treated for cavitary tuberculosis during 1980-1993 were tested by smear, culture and DNA amplification, as were 34 controls with no history of tuberculosis or pulmonary scars. RESULTS: No active tuberculosis cases were identified. All specimens were negative on DNA amplification and smear. Eight specimens from six subjects were positive on culture, revealing atypical mycobacteria. CONCLUSION: No genetic Mycobacterium tuberculosis material in sputum specimens of subjects with residual lesions of pulmonary tuberculosis and no false-positive amplification results were detected.

Evaluation of commercial DNA and rRNA amplification assays for assessment of treatment outcome in pulmonary tuberculosis patients.

To evaluate the clinical utility of the DNA and RNA amplification assays in monitoring the efficacy of tuberculosis treatment, 416 sputum specimens collected from 15 smear-positive tuberculosis patients during and after treatment were tested for the presence of Mycobacterium tuberculosis by microscopy, culture, polymerase chain reaction (Cobas Amplicor Mycobacterium Tuberculosis Test; Roche, Switzerland) and AMTDT 2 (Amplified Mycobacterium Tuberculosis Direct Test; Gen Probe, USA). All patients were cured, and no relapses were found. Results of both amplification assays re mained positive longer than results of either smear or culture. Four of 15 patients were positive by polymerase chain reaction and/or AMTDT 2 at the completion of treatment. Subsequent sputum specimens from these patients converted to negative within 2.5-12 months. The present data do not support the routine use of qualitative amplification assays for monitoring the treatment response of smear-positive tuberculosis patients.

Detection of Mycobacterium tuberculosis complex in sputum specimens by the automated Roche Cobas Amplicor Mycobacterium Tuberculosis Test.

Three hundred twenty-four sputum specimens from 151 patients with suspected active pulmonary tuberculosis were tested for the presence of the Mycobacterium tuberculosis complex with auramine fluorochrome stain and automated PCR assay (Roche Cobas Amplicor Mycobacterium Tuberculosis Test [MTB]). The results were compared with those of the conventional Löwenstein-Jensen tube culture and the BACTEC radiometer liquid culture. A total of 76 specimens from 32 patients were culture positive for M. tuberculosis. In addition, 37 specimens from 15 patients were smear and culture positive for other Mycobacterium species but negative by the present nucleic acid amplification method and thus were not included in the comparison. Compared with culture, the sensitivities, specificities, and positive and negative predictive values for acid-fast smear were 67, 98, 93, and 91% and those for the Cobas Amplicor MTB were 83, 99, 97, and 95%, respectively. When three consecutive sputum specimens per patient could be obtained, the sensitivity of the Cobas Amplicor MTB improved to 91%, whereas the sensitivity of the acid-fast smear remained unchanged.