Clinical significance of an equivocal interferon γ release assay result

Br J Ophthalmol. 2012 Feb;96(2):284-8. doi: 10.1136/bjo.2011.204578. Epub 2011 May 10.


Aim: To identify clinical risk factors for obtaining an 'equivocal' T-SPOT.TB result in patients consistent with tuberculosis (TB)-associated uveitis (TAU).

Methods: Prospective cohort study of consecutive new patients, with ocular signs consistent with TAU at a single tertiary centre enrolled over 15 months. All subjects underwent ocular and systemic evaluation, and investigations to rule out underlying disease. Subjects with underlying disease and interdeterminate T-SPOT.TB results were excluded. Patients were followed up for 1 year from enrolment.

Results: 15 of 155 subjects (9.67%) obtained 'equivocal' T-SPOT.TB results. Mean age was 52.2 (range 12-77) years. Most of the subjects were Chinese (n=8, 53.3%) with no sex dominance (seven male, eight female). None were immunocompromised. Patients aged <13 or >55 years old were found to be more likely to have an 'equivocal' T-SPOT.TB result (OR 21.2; 95% CI 3.7 to 121.6; p=0.001), while adjusting for possible confounders including sex, race, history of diabetes mellitus, disease duration, type of uveitis and tuberculin skin test positivity. These patients are more likely to be QuantiFERON-TB Gold In-tube negative (OR 14.7; 95% CI 1.2 to 179.9; p=0.035).

Conclusion: An 'equivocal' T-SPOT.TB result is associated with patients aged >55 years. Such patients are likely to have a negative QuantiFERON-TB Gold In-tube result.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Female
  • Follow-Up Studies
  • Humans
  • Interferon-gamma / blood*
  • Male
  • Middle Aged
  • Prospective Studies
  • Risk Factors
  • T-Lymphocytes / immunology
  • Tuberculin Test*
  • Tuberculosis, Ocular / diagnosis*
  • Uveitis / diagnosis*
  • Young Adult


  • Interferon-gamma