Table 1

 Results of IFN-γ release assays from the 12 patients out of 17 with tests categorised as “failed”, in which the test failed as a result of a high nil control

PatientAge(years)Nil control(IU/ml IFN-γ)ESAT-6(IU/ml IFN-γ)ESAT-6 – Nil(IU/ml IFN-γ)CFP-10(IU/ml IFN-γ)CFP-10 – Nil(IU/ml IFN-γ)Criteria 1*Criteria 2*
*Criteria 1: Current guidelines at the time of our study (see text). Criteria 2: Modified guidelines from manufacturer US package insert and CDC2 which state that a test may be interpreted as positive when the background level of IFN-γ is above 0.7 IU/ml only if the response to the corrected ESAT-6 or CFP-10 result is at least 50% greater than the background level; otherwise the result is indeterminate.
†IFN-γ levels above 15 IU/ml cannot be measured accurately.
11423.48†24.29† 0.81 24.23† 0.75 IndeterminateIndeterminate
21322.63†36.27† 13.64 32.44† 9.81 IndeterminateIndeterminate
3619.74†20.23† 0.49 20.25† 0.51 IndeterminateIndeterminate
41311.1611 −0.16 10.95 −0.21 IndeterminateIndeterminate
5169.028.75 −0.27 9.51 0.49 IndeterminateIndeterminate
688.027.17 −0.85 8.17 0.15 IndeterminateIndeterminate
782.512.64 0.13 1.82 −0.69 IndeterminateIndeterminate
822.192.48 0.29 2.54 0.35 IndeterminateIndeterminate
9121.583.01 1.43 2.32 0.74 IndeterminatePositive
10141.521.81 0.29 2.17 0.65 IndeterminateIndeterminate
1191.241.31 0.07 1.31 0.07 IndeterminateIndeterminate
1261.131.11 −0.02 1.05 −0.08 IndeterminateIndeterminate