Paradox of serial interferon-gamma release assays: variability width more important than specificity size.

Journal Article (Journal Article)

SETTING: Serial screening for latent tuberculous infection (LTBI) is commonly performed in certain populations, such as health care workers. The high apparent conversion rate in some studies of interferon-gamma release assays is puzzling given the claimed high specificity of these tests. OBJECTIVE: To understand how test-retest variability, specificity, and underlying LTBI prevalence affect observed outcomes of repeated testing for LTBI. DESIGN: Mathematical model assuming constant test sensitivity and specificity over time and no new infections. RESULTS: Test-retest variability had a large effect on the observed proportion of conversions (initial negative test, followed by a positive test) and reversions (initial positive test, followed by a negative test). For example, a test with 70% specificity and 5% test-retest variability would be associated with a conversion rate of 3.7% and a reversion rate of 7.7%, while a test with 95% specificity but 10% test-retest variability would be associated with a conversion rate of 5.5% and a reversion rate of 57%, assuming that both tests are 80% sensitive and underlying LTBI prevalence was 5%. CONCLUSION: Test-retest variability is a key parameter that should be reported for tests used for serial screening for LTBI. Reducing test-retest variability can reduce false-positive and false-negative results.

Full Text

Duke Authors

Cited Authors

  • Stout, JE; Belknap, R; Wu, Y-J; Ho, CS

Published Date

  • May 1, 2018

Published In

Volume / Issue

  • 22 / 5

Start / End Page

  • 518 - 523

PubMed ID

  • 29663956

Pubmed Central ID

  • PMC9132738

Electronic International Standard Serial Number (EISSN)

  • 1815-7920

Digital Object Identifier (DOI)

  • 10.5588/ijtld.17.0650


  • eng

Conference Location

  • France