| Objective: To evaluate the use of Phage Amplified Biological (PhaB) assay, Minimum inhibitory concentration (MIC) method and Absolute density method in drug susceptibility testing of Pyrazinamide (PZA) in clinical isolation of Mycobacterium tuberculosis (MTB).Methods: PZA resistantance of clinical isolation of MTB was detected by PhaB assay, MIC and absolute density method respectively, and the results of these three methods were compared.Results: There were 21, 33 and 22 strains of PZA sensitive isolations as well as 69, 57 and 68 of PZA resistant isolations were detected by absolute density method, MIC and PhaB assay respectively. If the result of absolute density method was set as the golden standard, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PhaB assay were 94.2%, 85.7%, 95.6%, 81.8% and 92.2% respectively; That were 96.5%, 63.6%, 82.1%, 95.5% and 84.4% respectively if the result of MIC was set as the golden standard. The sensitivity, specificity, PPV, NPV and accuracy of PhaB assay were 96.4%, 90.0%, 96.4%, 90.0% and 94.7% respectively if the results of MIC and PhaB were set as the golden standard.Conclusions: The MIC method is helpful for the choice of drug, but the testing time is too long to adapt to the clinical use. The PhaB assay is highly sensitive and specific and its results are highly consistent with those of the absolute density method. It is easy to be used and takes only three days in the detection of drug susceptibility of PZA in clinicical isolations of MTB. The result indicates this low-cost assay can be used in rapid screening for PZA resistance in MTB isolation. |
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