Table 5.

Estimated Test Characteristics and Frequency of Under/Overdiagnosis of LTBI Using Varying Prevalence and Test Cutoffs^a

	TST			QFT			TSPOT
	≥5 mm	≥10 mm	≥15 mm	≥0.35 IU/mL	≥0.70 IU/mL	≥1.00 IU/mL	≥5 spots	≥6 spots	≥7 spots	≥8 spots
Sensitivity	51.7	44.8	27.8	77.3	57.1	50.6	56.7	53.2	51.7	51.6
Specificity	97.0	97.8	99.4	96.7	98.0	98.4	98.9	99.4	99.6	99.8
1% LTBI Prevalence
Underdiagnosed LTBI	4.8	5.5	7.2	2.3	4.3	4.9	4.3	4.7	4.8	4.8
Overdiagnosed LTBI	30.4	22.1	5.6	32.8	19.1	15.4	8.5	4.0	3.6	2.0
5% LTBI prevalence
Underdiagnosed LTBI	24.2	27.6	36.1	11.3	21.5	24.7	21.7	23.4	24.2	24.2
Overdiagnosed LTBI	29.2	21.2	5.4	31.7	18.7	15.2	8.2	3.8	3.4	1.9
15% LTBI prevalence
Underdiagnosed LTBI	72.5	82.8	108.2	34.0	64.4	74.0	65.0	70.1	72.5	72.5
Overdiagnosed LTBI	26.1	19.0	4.8	28.4	16.8	13.6	9.3	5.4	3.7	1.3

Abbreviations: LTBI, latent tuberculosis infection; QFT, QuantiFERON Gold In-Tube; TSPOT, T-SPOT; TB; TST, tuberculin skin test.

^aEstimates of diagnostic test characteristics differ slightly from Table 3 due to differences in analytic techniques as described in the methods section. Underdiagnosed LTBI cases: Number of LTBI diagnoses missed per 1000 screened Overdiagnosed LTBI cases: Number of LTBI misdiagnoses per 1000 screened.