Table 3

Summary of the diagnostic indices for Xpert Ultra, smear and culture in BAL samples

BALXpert Ultra (trace as positive)Xpert Ultra (trace as negative)P value*SmearP value*CultureP value*
Reference standard: culture-positive TB from BAL samples (category 1)
 Positive tests19/2116/218/2121/21
 Sensitivity0.91 (0.82 to 0.98)0.76 (0.69 to 0.83)0.0830.380.00091.00 (0.91 to 1.00)
 Specificity1.00 (0.99 to 1.00)1.00 (0.99 to 1.00)0.99 (0.98 to 1.00)1.00 (0.99 to 1.00)
 PPV1.00 (0.90 to 1.00)1.00 (0.88 to 1.00)0.80 (0.65 to 0.95)1.00 (0.91 to 1.00)
 NPV0.99 (0.98 to 1.00)0.98 (0.97 to 0.99)0.94 (0.94 to 0.96)0.99 (0.99 to 1.00)
Reference standard: culture-positive TB from all respiratory samples (adjusted category 1)
 Positive tests20/2417/248/2421/24
 Sensitivity0.83 (0.77 to 0.90)0.71 (0.66 to 0.76)0.0810.320.00050.88 (0.80 to 0.95)0.502
 Specificity1.00 (0.99 to 1.00)1.00 (0.99 to 1.00)0.99 (0.98 to 1.00)1.00 (0.99 to 1.00)
 PPV1.00 (0.90 to 1.00)1.00 (0.88 to 1.00)0.80 (0.65 to 0.95)1.00 (0.91 to 1.00)
 NPV0.98 (0.98 to 0.99)0.97 (0.96 to 0.98)0.94 (0.93 to 0.94)0.99 (0.98 to 1.00)
Reference standard: clinical diagnosis of TB—culture-confirmed TB (category 1) and highly probable TB (category 2)
 Positive tests20/3217/328/3221/32
 Sensitivity0.63 (0.59 to 0.66)0.53 (0.52 to 0.55)0.0780.250.00050.66 (0.62 to 0.69)0.564
 Specificity1.00 (0.99 to 1.00)1.00 (0.99 to 1.00)0.99 (0.98 to 1.00)1.00 (0.99 to 1.00)
 PPV1.00 (0.90 to 1.00)1.00 (0.88 to 1.00)0.80 (0.65 to 0.95)1.00 (0.91 to 1.00)
 NPV0.95 (0.95 to 0.96)0.94 (0.93 to 0.95)0.91 (0.90 to 0.92)0.96 (0.95 to 0.96)
  • *Comparing sensitivity versus Xpert Ultra (trace as positive)—with Bonferroni correction factor.

  • BAL, bronchoalveolar lavage; NPV, negative predictive value; PPV, positive predictive value; TB, tuberculosis.