Journal List > Korean J Clin Microbiol > v.11(1) > 1038145

Jung, Kim, Seo, and Lee: Clinical Usefulness of Real-time PCR and Amplicor MTB PCR Assays for Diagnosis of Tuberculosis

Abstract

Background

PCR assay has provided a mean of more rapid and sensitive detection of Mycobacterium tuberculosis (MTB) complex than conventional acid-fast bacilli (AFB) smears and MTB cultures. Using the recently developed AdvanSure TB/NTM kit (LG Life Science Diagnostic Division, Korea), which could differentiate nontuberculous mycobacteria (NTM) from MTB, this study compared clinical usefulness of real-time PCR assay and Amplicor MTB PCR assay (Roche Molecular Systems, USA) for diagnosis of tuberculosis.

Methods

A total of 213 specimens (148 respiratory and 65 nonrespiratory specimens) were tested by using real-time PCR, Amplicor MTB PCR, AFB smear, and MTB culture. The sensitivity and specificity of four methods were evaluated according to clinical diagnosis.

Results

Of six NTM grown in culture, four (67%) were detected by real-time PCR. The overall agreement of real-time and Amplicor MTB PCR was 92% (191/207). The overall sensitivity and specificity were 91% and 87%, respectively, for real-time PCR, and 86% and 93% for Amplicor MTB PCR. In nonrespi-ratory specimens, the sensitivities of real-time PCR, Amplicor MTB PCR, AFB smear, and MTB culture were 67%, 60%, 13%, and 40%, respectively, and the specificity of the four methods were all 100%.

Conclusion

For diagnosis of tuberculosis, the sensitivity and specificity of the real-time PCR assay using AdvanSure TB/NTM kit and Amplicor MTB PCR were similar, and the former could differentiate NTM from MTB. The PCR assay can be considered as a more sensitive technique for the detection of MTB than the conventional AFB smear and culture.

References

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Table 1.
Results of 6 cases of nontuberculous mycobacteria (NTM)
No. Case Specimen Real-time PCR Amplicor MTB PCR AFB smear Culture
1 Sputum NTM Neg 1+ NTM∗
2 Sputum NTM Neg 3+ NTM∗
3 Urine NTM Neg 3+ M. avium
4 Sputum NTM Neg Neg M. abscessus
5 Sputum Neg Neg Neg M. fortuitum
6 Bronchial Neg Neg Neg M. intracellulare
  aspirate        

The identification tests were not performed. Abbreviations: MTB, Mycobacterium tuberculosis; AFB, acid-fast bacilli; Neg, negative.

Table 2.
Comparison of results between real-time PCR and Amplicor MTB PCR assays for detection of MTB
    Real-time PCR
TB (+) TB (−) Total
Amplicor MTB PCR TB (+) TB (−) Total 88∗ 13 101 3 103∗ 106 91 116 207

Concordance rate between real-time PCR and Amplicor MTB PCR was 92% (191/207). Abbreviations: MTB, Mycobacterium tuberculosis; TB, tuberculosis.

Table 3.
Sensitivity, specificity, predictive values of real-time PCR, Amplicor MTB PCR, AFB smear and culture for detection of MTB in all 207 specimens according to clinical diagnosis
  Sensitivity (%) Specificity (%) P value∗ Predictive Positive value (%) Negative
Real-time PCR 91 87   86 92
Amplicor MTB PCR 86 93 0.324 91 89
AFB smear 46 100 0.000 100 68
Culture 59 100 0.000 100 74

Statistical analysis between real-time PCR and other methods (Amplicor MTB PCR, AFB, and culture) by chi-square test. Abbreviations: MTB, Mycobacterium tuberculosis; AFB, acid-fast bacilli.

Table 4.
Sensitivity and specificity of real-time PCR, Amplicor MTB PCR, AFB smear and culture for detection of MTB according to respiratory and nonrespiratory specimens
  Sensitivity (%) Specificity (%) P value∗
  Resp NonR Resp NonR Resp NonR
Real-time PCR 95 67 77 100    
Amplicor MTB PCR 91 60 87 100 0.276 0.804
AFB smear 52 13 100 100 0.000 0.015
Culture 63 40 100 100 0.000 0.285

Statistical analysis between real-time PCR and other methods (Amplicor MTB PCR, AFB smear, and culture) by chi-square test. Abbreviations: MTB, Mycobacterium tuberculosis; AFB, acid-fast bacilli; Resp, respiratory specimens; NonR, nonrespiratory specimens.

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