Interferon-Gamma Release Assays versus Tuberculin Skin Testing for the Diagnosis of Latent Tuberculosis Infection: An Overview of the Evidence

Table 1

Comparison of TST and IGRA regarding several tests' characteristics.

Test characteristics	TST	QFT	T-SPOT.TB
Overall sensitivity [22]	77%	78%	92%
HIV uninfected [9]		84%	88%
HIV infected [18]		65%	68%
Overall specificity [22]	97%	98%	93%
HIV uninfected		NA	NA
HIV infected [18]		52%	61%
Decreased specificity if BCG vaccinated?	Yes, particularly if done after infancy or repeatedly [22]		No effect [22]
Prone to nonspecific variations in test results?	Yes, from reader variability [10]		Yes, from innumerous factors; [23–28]
Thresholds for conversions evidence based?	Yes [15]	No	No
Prone to conversions?	Yes, mostly due to TB exposure		Yes (high when only; negative-positive definitions; are used) [29]
Prone to reversions?	Yes [29]		High in individuals with weak; IGRA positivity and discordance; with TST [29]
Boosting?	Yes [15]		Yes, possibly if given 3 days; after performing TST [24]
Conversion associated with risk of progression to active TB?	Yes (strong evidence)		No direct evidence
Ability to detect those at high risk of developing active TB	Weak [30, 31]		Weak [30, 31]
Preventive treatment of individuals with conversion reduces risk of progression to active TB?	Yes [19, 20]		No evidence