Summary of findings 4. Xpert Ultra and Xpert MTB/RIF for rifampicin resistance.
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Participants: people with tuberculosis detected by Xpert Ultra or Xpert MTB/RIF Role: initial test, replacement test for standard practice, which includes culture‐based drug susceptibility testing or line probe assay Settings: primarily tertiary care centres, the index test was often run in central (reference laboratories), where drug susceptibility testing for the reference standard could be performed Index tests: Xpert Ultra and Xpert MTB/RIF Reference standard: culture‐based drug susceptibility testing using solid or liquid media or line probe assay Studies: cross‐sectional studies Xpert Ultra pooled sensitivity (95% CrI): 100.0% (95.1 to 100.0); pooled specificity (95% CrI): 100.0% (99.0 to 100.0) Xpert MTB/RIF pooled sensitivity (95% CrI): 96.5% (91.9 to 98.8); pooled specificity (95% CrI): 99.1% (98.0 to 99.7) | |||||
| Xpert Ultra result | 1000 people tested for rifampicin resistance using Xpert Ultra (95% Crl) | Number of participants (studies) | Certainty of the evidence (GRADE) | ||
| Prevalence of 2% | Prevalence of 10% | Prevalence of 15% | |||
| True‐positives (patients correctly classified as rifampicin resistant) | 20 (19 to 20) | 100 (95 to 100) | 150 (143 to 150) | 24 (4) | ⊕⊕⊝⊝ Lowa,b |
| False‐negatives (patients incorrectly classified as rifampicin susceptible) | 0 (0 to 1) | 0 (0 to 5) | 0 (0 to 7) | ||
| True‐negatives (patients correctly classified as rifampicin susceptible) | 980 (979 to 980) | 900 (899 to 900) | 850 (849 to 850) | 105 (4) | ⊕⊕⊕⊝ Moderatea |
| False‐positives (patients incorrectly classified as rifampicin resistant) | 0 (0 to 1) | 0 (0 to 1) | 0 (0 to 1) | ||
| Xpert MTB/RIF result | 1000 people tested for rifampicin resistance using Xpert MTB/RIF (95% Crl) | Number of participants (studies) | Certainty of the evidence (GRADE) | ||
| Prevalence of 2% | Prevalence of 10% | Prevalence of 15% | |||
| True‐positives (patients correctly classified as rifampicin resistant) | 19 (18 to 20) | 97 (92 to 99) | 145 (138 to 148) | 148 (19) | ⊕⊕⊕⊕ High |
| False‐negatives (patients incorrectly classified as rifampicin susceptible) | 1 (0 to 2) | 3 (1 to 8) | 5 (2 to 12) | ||
| True‐negatives (patients correctly classified as rifampicin susceptible) | 971 (960 to 977) | 892 (882 to 897) | 842 (833 to 847) | 822 (19) | ⊕⊕⊕⊕ High |
| False‐positives (patients incorrectly classified as rifampicin resistant) | 9 (3 to 20) | 8 (3 to 18) | 8 (3 to 17) | ||
Abbreviations: Crl: credible interval; TB: tuberculosis.
We included plausible prevalence estimates for the target condition suggested by the WHO. For Xpert Ultra, the median prevalence of rifampicin resistance in the included studies was 19.2%. For Xpert MTB/RIF, the median prevalence of rifampicin resistance in the included studies was 11.9%.
aAll these studies were conducted in China (high TB‐burden country). Applicability to other settings comes with some uncertainty and therefore we downgraded one level for indirectness. bThere was a low number of participants contributing to this analysis for the observed sensitivity. We downgraded one level for imprecision.
GRADE certainty of the evidence
High: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
The results presented in this table should not be interpreted in isolation from results of the individual included studies contributing to each summary test accuracy measure.