Hi Dr Preet
In a Mexican study, they conclude
The GeneXpert MTB/RIF TestTM used in the study of 693 patients with the presuntive diagnosis of extrapulmonary tuberculosis showed numerous advantages over the conventional techniques: shorter time of obtention of results (hours versus days). High sensitivity (73.2%) and specifi city (100%) –its sensitivity, considering only the isolations of Mycobacterium tuberculosis complex, was 100%–, the additional determination of rifampin resistance, and its technical simplicity. Its disadvantages were: no detection of strains other than the Mycobacterium tuberculosis complex (26.8% of the cases) and its high cost.
http://www.medigraphic.com/pdfs/patol/pt-2014/pt143d.pdf
in this other study the following is reported:
The results of the analyzes are presented for the samples and patients. Of the 372 specimens analyzed, 39 (10.5%) were positive for M. tuberculosis in the Xpert® MTB / RIF test, and 23 the samples, especially of tissues, came from patients with a diagnosis of HIV infection, with 27 detections (7.2%), followed by liquid cerebrospinal fluid with seven (1.8%). The crop was positive in 31 samples (8.3%); 22 of these isolates corresponded to total tissues (6%) and nine (3%) were of liquids; 12 samples had smear positive (3.2%) (figure 1). The proof molecular of two of the samples was negative, but the culture was positive (table 2). The sensitivity and specificity of the test Xpert® MTB / RIF compared with those of the crop
were 93.5% (95% CI 95.2-100) and 97% (95% CI 95.1-99), respectively; its predictive value positive was 74.3% (95% CI 59.3-89.3) and the negative, of 99.4% (95% CI 98.4-100). He analysis stratified by anatomical site evidenced sensitivities greater than 75% for liquids and for the tissues, but it could not be determined in abscesses due to the few samples. The
stratified specificity for eight of the 12 different types of samples, it was recorded in a range between 66 and 100% (table 2).
http://www.scielo.org.co/pdf/bio/v36s1/v36s1a11.pdf
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