Sputum monitoring during tuberculosis treatment for predicting outcome: systematic review and meta-analysis

Abstract

WHO has previously recommended sputum-smear examination at the end of the second month of treatment in patients with recently diagnosed pulmonary tuberculosis, and, if positive, extension of the intensive therapy phase. We did a systematic review and meta-analysis to assess the accuracy of a positive sputum smear or culture during treatment for predicting failure or relapse in pulmonary tuberculosis. We searched PubMed, Embase, and the Cochrane Library for studies published in English through December, 2009. We included randomised controlled trials, cohort, and case-control studies of previously untreated pulmonary tuberculosis patients who had received a standardised regimen with rifampicin in the initial phase. Accuracy results were summarised in forest plots and pooled by use of a hierarchical regression approach. 15 papers (28 studies) met the inclusion criteria. The pooled sensitivities for both 2-month smear (24% [95% CI 12-42%], six studies) and culture (40% [95% CI 25-56%], four studies) to predict relapse were low. Corresponding specificities (85% [95% CI 72-90%] and 85% [95% CI 77-91%]) were higher, but modest. For failure, 2-month smear (seven studies) had low sensitivity (57% [95% CI 41-73%]) and higher, although modest, specificity (81% [95% CI 72-87%]). Both sputum-smear microscopy and mycobacterial culture during tuberculosis treatment have low sensitivity and modest specificity for predicting failure and relapse. Although we pooled a diverse group of patients, the individual studies had similar performance characteristics. Better predictive markers are needed.

Figure 1

Study selection process. TB: tuberculosis.

Figure 2

Sub-group Selection.

Figure 3

Positive sputum specimen as a predictor of relapse. The circles and the lines represent the point estimates and 95% CIs, respectively. The size of the circle indicates the study size. Cp, culture positive; sp, sputum smear positive; the number following cp or sp indicates the month the sputum specimen was examined. Sensitivity is the proportion of relapsed subjects who had a positive sputum examination. Specificity is the proportion of subjects who did not relapse and had a negative sputum examination.

Figure 4

Positive sputum specimen as a predictor of failure. The circles and the lines represent the point estimates and 95% CIs, respectively. The size of the circle indicates the study size. Cp, culture positive; sp, sputum positive; the number following cp or sp indicates the month the sputum specimen was examined. Sensitivity is the proportion of subjects who experienced treatment failure and had a positive sputum examination. Specificity is the proportion of subjects who did not experience treatment failure and had a negative sputum examination.