Use of a Molecular Diagnostic Test in AFB Smear Positive Tuberculosis Suspects Greatly Reduces Time to Detection of Multidrug Resistant Tuberculosis

Background: The WHO has recommended the implementation of rapid diagnostic tests to detect and help combat M/XDR tuberculosis (TB). There are limited data on the performance and impact of these tests in field settings. Methods: The performance of the commercially available Genotype MTBDRplus molecular assay was compared to conventional methods including AFB smear, culture and drug susceptibility testing (DST) using both an absolute concentration method on Löwenstein-Jensen media and broth-based method using the MGIT 960 system. Sputum specimens were obtained from TB suspects in the country of Georgia who received care through the National TB Program. Results: Among 500 AFB smear-positive sputum specimens, 458 (91.6%) had both a positive sputum culture for Mycobacterium tuberculosis and a valid MTBDRplus assay result. The MTBDRplus assay detected isoniazid (INH) resistanc

Sputum culture results for all AFB smear positive tuberculosis suspects and corresponding complete MTBDRplus assay results.

<p>Sputum culture results for all AFB smear positive tuberculosis suspects and corresponding complete MTBDRplus assay results.</p

Distribution of MTBDR<i>plus</i> assay results according to phenotypic drug resistance patterns using conventional drug susceptibility testing for specimens with both valid culture and MTBDRplus assay results.

<p>Distribution of MTBDR<i>plus</i> assay results according to phenotypic drug resistance patterns using conventional drug susceptibility testing for specimens with both valid culture and MTBDRplus assay results.</p

Average time to results in days for detection of TB and associated drug resistance (N = 458)^*.

<p>*Values are average number of days with one standard deviation in parentheses.</p>∧<p>DST = drug susceptibility testing.</p

Performance parameters of MTBDR<i>plus</i> in detecting INH R^∧, RIF R^∧, and MDR^∧ compared to conventional DST (reference standard)^#.

#<p>Values are percentages with 95% confidence interval in parentheses.</p><p>*PPV = positive predictive value, NPV = negative predictive value.</p>∧<p>INH R = isoniazid resistance, RIF R = rifampin resistance, MDR = multidrug resistance.</p

Pattern of genetic mutations in phenotypic drug-resistant <i>Mycobacterium tuberculosis</i> isolates using the Genotype MTBDRplus assay.

<p>*Definitions of abbreviations: INH = isoniazid; RIF = rifampicin; MDR = multidrug-resistant.</p>∧<p>Values are numbers, with percentages in parentheses.</p