Table 5.

Quality assessment of both commercial IGRAs

IGRAComponent of within-test variabilityDescriptionNo. of subjects (total no. of measures)Intraclass correlation coefficient of continuous measures (95% CI)
QFTaTest-retest reproducibilitybDuplicate 1 versus duplicate 235 (70)0.996 (0.992–0.998)
ELISA reader reliabilityRepeated readings of optical density at 0, 5, 15, 30, and 60 min35 (175)0.998 (0.997–0.999)
T-SPOTTest-retest reproducibilitybDuplicate 1 versus duplicate 28 (16)0.993 (0.967–0.999)
  • a The correlation coefficient (r) of the standard curve, which was calculated from the mean absorbance values of the internal standards, was >0.999 for each QFT ELISA run.

  • b There was perfect agreement of all dichotomous measures (raw, 100%; kappa coefficient, 1.000).