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

Patient	Age(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.
1	14	23.48†	24.29†	0.81	24.23†	0.75	Indeterminate	Indeterminate
2	13	22.63†	36.27†	13.64	32.44†	9.81	Indeterminate	Indeterminate
3	6	19.74†	20.23†	0.49	20.25†	0.51	Indeterminate	Indeterminate
4	13	11.16	11	−0.16	10.95	−0.21	Indeterminate	Indeterminate
5	16	9.02	8.75	−0.27	9.51	0.49	Indeterminate	Indeterminate
6	8	8.02	7.17	−0.85	8.17	0.15	Indeterminate	Indeterminate
7	8	2.51	2.64	0.13	1.82	−0.69	Indeterminate	Indeterminate
8	2	2.19	2.48	0.29	2.54	0.35	Indeterminate	Indeterminate
9	12	1.58	3.01	1.43	2.32	0.74	Indeterminate	Positive
10	14	1.52	1.81	0.29	2.17	0.65	Indeterminate	Indeterminate
11	9	1.24	1.31	0.07	1.31	0.07	Indeterminate	Indeterminate
12	6	1.13	1.11	−0.02	1.05	−0.08	Indeterminate	Indeterminate