The usefulness of interferon-gamma release assay for diagnosis of tuberculosis-related uveitis in Korea

Abstract

Purpose: To evaluate the usefulness of the interferon-gamma release assay (IGRA) for diagnosing tuberculosis (TB)-related uveitis (TRU).

Methods: Records from 181 patients with ocular signs and symptoms suggestive of TRU and intraocular inflammation of unknown etiology were reviewed. All subjects underwent clinical and laboratory testing, including IGRA, to rule out presence of underlying disease. A diagnosis of presumed TRU was made based on an internist's TB diagnosis and a patient's response to anti-TB therapy. Sensitivity, specificity, and positive predictive values of IGRA for TRU diagnosis were calculated. Clinical characteristics were compared between patients with positive and negative IGRA results.

Results: The sensitivity and specificity of IGRA for TRU were 100% and 72.0%, respectively. Mean age, percentage of patients with retinal vasculitis, and the anatomic type of uveitis were significantly different between patients with positive and negative IGRA results (all p ≤ 0.001). Positive IGRA rates and false-positive rates were significantly different between age and anatomic type groups (both p = 0.001). The positive predictive value of the IGRA among patients with intraocular inflammation was high (70%) when all of younger age (≤ 40 years), posterior uveitis, and retinal vasculitis were present.

Conclusions: The IGRA is useful for diagnosing TRU in the Korean population, especially when it is used as a screening test. Clinical characteristics, including younger age (≤ 40 years), posterior uveitis, and retinal vasculitis in IGRA-positive patients, increase the likelihood of the patient having TRU.

Keywords: Age; Interferon-gamma release tests; Retinal vasculitis; Tuberculosis; Uveitis.

Fig. 1

Diagnosis of presumed tuberculosis (TB)-related uveitis. (A) Fundus photograph (left) and early (middle) and late (right) phase fluorescein angiogram (FA) images from the right eye of an 18-year-old man at the initial clinical visit. Temporal retinal vasculitis with vascular sheathing, exudate, retinal hemorrhage, and vitreous haze were noted. The patient had a positive interferon-gamma release assay result and was referred to a pulmonologist, who made a diagnosis of pulmonary TB, confirmed with a positive Mycobacterium tuberculosis culture and high-resolution computed tomography. (B) Fundus photograph and FA image of the right eye showing remission after scatter laser therapy and 6 months of anti-tuberculosis medication.

Fig. 2

Interferon-gamma release assay (IGRA)-positive rates (A) and false-positive rates (B) among the five age groups examined. Both rates were significantly different among age groups (all p-values <0.001). p-values were obtained by chi-square tests for trend.

Fig. 3

Interferon-gamma release assay (IGRA)-positive rates among the four anatomic types of uveitis and between patients with and without retinal vasculitis. (A) The IGRA-positive rates were significantly different among the four anatomic groups (p = 0.001). (B) Patients with retinal vasculitis had higher positive IGRA rate (p < 0.001) than those without retinal vasculitis. p-values were obtained using chi-square tests.

Fig. 4

Positive predictive values of the interferon-gamma release assay for presumed tuberculosis-related uveitis in patients with intraocular inflammation (A) in the age groups and (B) in the anatomic type subgroups.