Comparative Study of a Real-Time PCR Assay Targeting senX3-regX3 versus Other Molecular Strategies Commonly Used in the Diagnosis of TuberculosisReport as inadecuate




Comparative Study of a Real-Time PCR Assay Targeting senX3-regX3 versus Other Molecular Strategies Commonly Used in the Diagnosis of Tuberculosis - Download this document for free, or read online. Document in PDF available to download.

Background

Nucleic acid amplification tests are increasingly used for the rapid diagnosis of tuberculosis. We undertook a comparative study of the efficiency and diagnostic yield of a real-time PCR senX3-regX3 based assay versus the classical IS6110 target and the new commercial methods.

Methods

This single-blind prospective comparative study included 145 consecutive samples: 76 from patients with culture-confirmed tuberculosis 86.8% pulmonary and 13.2% extrapulmonary tuberculosis: 48.7% smear-positive and 51.3% smear-negative and 69 control samples 24 from patients diagnosed with non-tuberculous mycobacteria infections and 45 from patients with suspected tuberculosis which was eventually ruled out. All samples were tested by two CE-marked assays Xpert®MTB-RIF and AnyplexTM plus MTB-NTM and two in-house assays targeting senX3-regX3 and the IS6110 gene.

Results

The detection limit ranged from 1.00E+01 fg for Anyplex, senX3-regX3 and IS6110 to 1.00E+04 fg for Xpert. All three Xpert, senX3-regX3 and IS6110 assays detected all 37 smear-positive cases. Conversely, Anyplex was positive in 34 91.9% smear-positive cases. In patients with smear-negative tuberculosis, differences were observed between the assays; Xpert detected 22 56.41% of the 39 smear-negative samples, Anyplex 24 61.53%, senX3-regX3 28 71.79% and IS6110 35 89.74%. Xpert and senX3-regX3 were negative in all control samples; however, the false positive rate was 8.7% and 13% for Anyplex and IS6110, respectively. The overall sensitivity was 77.6%, 85.7%, 77.3% and 94.7% and the specificity was 100%, 100%, 90.8% and 87.0% for the Xpert, senX3-regX3, Anyplex and IS6110 assays, respectively.

Conclusion

Real-time PCR assays targeting IS6110 lack the desired specificity. The Xpert MTB-RIF and in-house senX3-regX3 assays are both sensitive and specific for the detection of MTBC in both pulmonary and extrapulmonary samples. Therefore, the real time PCR senX3-regX3 based assay could be a useful and complementary tool in the diagnosis of tuberculosis.



Author: Rocio Sanjuan-Jimenez , Inmaculada Toro-Peinado, Pilar Bermudez, Juan D. Colmenero, Pilar Morata

Source: http://plos.srce.hr/



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