Journal Article
|ResearchXpert(®) MTB/RIF for detection of Mycobacterium tuberculosis from frozen string and induced sputum sediments
Abstract
SETTING
Although it is now widely used for tuberculosis (TB) diagnosis, Xpert® MTB/RIF availability remains inadequate in low-resource settings. Moreover, its accuracy in testing stored samples from non-expectorating patients has not been evaluated.
OBJECTIVE
To assess the performance of Xpert in frozen samples of induced sputum (IS) and sputum from string test (ST) from non-expectorating individuals with presumed TB.
DESIGN
This was a laboratory-based study of 377 ST and IS samples collected between March 2010 and March 2013 at a referral hospital in Uganda. Samples were decontaminated, centrifuged and cultured, and the resultant samples were frozen at −20°C before Xpert evaluation.
RESULTS
TB was detected in ST and IS samples from 19/163 (11.7%) children and 63/201 (29.4%) adults using culture. Xpert sensitivity in frozen sediments from children was 37.5% (95%CI 8.5–75.5) in ST and 41.7% (95%CI 15.2–72.3) in IS samples, with specificities of respectively 100% (95%CI 94.9–100) and 98.6% (95%CI 92.7–100). In adults, sensitivity was respectively 50% (95%CI 31.3–68.7) and 48.5% (95%CI 30.8–66.4) in ST and IS samples, with specificities of respectively 100% (95%CI 95.5–100) and 98.6% (95%CI 92.4–100).
CONCLUSION
Given these results, and particularly the high specificity, the use of Xpert on frozen ST and IS sediment samples from both children and adults is promising.
Although it is now widely used for tuberculosis (TB) diagnosis, Xpert® MTB/RIF availability remains inadequate in low-resource settings. Moreover, its accuracy in testing stored samples from non-expectorating patients has not been evaluated.
OBJECTIVE
To assess the performance of Xpert in frozen samples of induced sputum (IS) and sputum from string test (ST) from non-expectorating individuals with presumed TB.
DESIGN
This was a laboratory-based study of 377 ST and IS samples collected between March 2010 and March 2013 at a referral hospital in Uganda. Samples were decontaminated, centrifuged and cultured, and the resultant samples were frozen at −20°C before Xpert evaluation.
RESULTS
TB was detected in ST and IS samples from 19/163 (11.7%) children and 63/201 (29.4%) adults using culture. Xpert sensitivity in frozen sediments from children was 37.5% (95%CI 8.5–75.5) in ST and 41.7% (95%CI 15.2–72.3) in IS samples, with specificities of respectively 100% (95%CI 94.9–100) and 98.6% (95%CI 92.7–100). In adults, sensitivity was respectively 50% (95%CI 31.3–68.7) and 48.5% (95%CI 30.8–66.4) in ST and IS samples, with specificities of respectively 100% (95%CI 95.5–100) and 98.6% (95%CI 92.4–100).
CONCLUSION
Given these results, and particularly the high specificity, the use of Xpert on frozen ST and IS sediment samples from both children and adults is promising.
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English
