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Clinical significance of an equivocal interferon γ release assay result
  1. Marcus Ang1,2,
  2. Wong Wanling2,3,
  3. Soon-Phaik Chee1,3
  1. 1Singapore National Eye Centre, Singapore
  2. 2Singapore Eye Research Institute, Singapore
  3. 3Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
  1. Correspondence to Associate Professor Soon-Phaik Chee, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751; chee.soon.phaik{at}


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.

  • Tuberculosis
  • interferon γ release assay
  • uveitis
  • infection

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  • Funding Singapore National Eye Centre Health and Research Endowment Fund.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval This study was approved by the Singapore Health Services Institutional Review Board in accordance with their guidelines.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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