[Comparison of four methods in the detection of isoniazid resistance in clinical isolates of Mycobacterium tuberculosis].
OBJECTIVE
To evaluate the use of phage amplified biologically (PhaB) assay, Bactec-960 system, minimum inhibitory concentration (MIC) method and gene chip in drug susceptibility testing of isoniazid (INH) in clinical isolates of Mycobacterium tuberculosis (MTB).


METHODS
INH resistance of 167 clinical isolates of MTB was detected by PhaB assay, Bactec-960 system, MIC and gene-chip methods respectively, and the results of these four methods were compared.


RESULTS
111 INH resistant isolates and 56 INH sensitive isolates were detected by Bactec-960 system. If the result of Bactec-960 system was set as the golden standard, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PhaB assay were 96.4%, 96.4%, 93.1%, 98.2%, and 96.4% respectively; the sensitivity, specificity, PPV, NPV, and accuracy were 92.9%, 99.1%, 98.1%, 96.5%, and 97.0% for the MIC method, and they were 83.9%, 96.4%, 92.2%, 92.2%, and 92.2% respectively for the gene-chip method. If the result of the MIC method was set as the golden standard, the sensitivity, specificity, PPV, NPV, and accuracy of PhaB assay were 100%, 95.6%, 91.4%, 100%, and 97.0% respectively. The sensitivity, specificity, PPV, NPV, and accuracy were 98.1%, 96.5%, 92.9%, 99.1%, and 97.0% for the Bactec-960 system, and they were 88.7%, 96.5%, 92.2%, 94.8%, and 94.0% respectively for the gene-chip method.


CONCLUSIONS
The PhaB assay is highly sensitive and specific, and its result is highly consistent with those of the Bactec-960 system and the MIC method. It is easy to use and took only three days in the detection of drug susceptibility of INH in clinical isolates of MTB. The results indicate that this low-cost assay can be used in rapid screening for INH resistance in MTB isolates. The MIC method proves to be as efficient as the Bactec-960 system, but whether it can be used as the standard method still needs further investigation. The sensitivity of the gene-chip method is lower as compared to the other methods, and therefore can only be used as an ancillary test.
Cui
Zhen-ling
ZL
Basic Laboratory of Tuberculosis, Shanghai Pulmonary Hospital-Tuberculosis Key Laboratory of Shanghai, Shanghai 200433, China.
Hu
Zhong-yi
ZY
Wang
Jie
J
Zhang
Ying-rong
YR
Chen
Hui-ping
HP
Weng
Xin-hua
XH
D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques / Q000379:methods*; D024881:Drug Resistance, Bacterial; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification; D021141:Nucleic Acid Amplification Techniques; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000382:microbiology*