Purpose:
To evaluate clinical and paraclinical parameters for the indirect diagnosis of tuberculosis-related uveitis (TRU). To investigate binary classification tests and concordance between tuberculosis skin test (TST) and QuantiFERON®-TB Gold (QF).
Methods:
Prospective 2-year study in a tertiary referral center in Spain. Patients with clinically suspected TRU were recruited consecutively. Demographical and clinical data were recorded. After thorough examination by an uveitis expert, QF, TST and chest X-ray were performed. Other possible uveitis etiologies were ruled out by ancillary tests. Further investigations were also performed case by case after consultation with an internist. TST was considered positive if strongly reactive (≥15mm) and QF interpreted according to the manufacturer instructions. After final assessment standard anti-tuberculosis therapy was started if TRU was considered highly probable. Finally, diagnosis of TRU was established according of Gupta & Gupta criteria and set as Gold Standard. Strength of association for TRU was determined by odds ratio and compared by Chi square test, Student's t-test or Fisher exact test. Concordance was assessed using kappa coefficients and binary classification tests included sensitivity (S) and specificity (Sp).
Results:
The study included 102 patients, 54 males and 48 females. Mean age at diagnosis was 44 years (10-88). Sixty nine (67.6%) patients were Spanish-born and 33 (32.3%) were foreign-born (16 from Asia: Pakistan, India and the Philippines). Final diagnosis included 31 (30.3%) cases of TRU and 71 (69.6%) cases with other diagnoses. Asian origin (OR 2.25 p<0.0001), previous tuberculosis (TB) contact (OR 2.38 p=0.047), TB in the past (OR 6.85 p=0.002), intermediate uveitis (IU) (OR 2.82 p=0.046) and vasculitis (OR 8.92 p<0.0001) were significantly related to TRU. S and Sp of the TST (≥15mm) and QF for this clinically selected uveitis population did not differ significantly (S 87% vs 90.3% and Sp 85.9% vs 81.6%, respectively) with excellent agreement between both tests (k=0.843). However, parameters improved when both tests were taken together (S 100%, Sp 90.1%).
Conclusions:
In a Western urban multi-ethnic population with a medium TB incidence, patients from Asia, TB history or contact in the past, IU and vasculitis are at higher risk of TRU. TST or QF are both equivalent and not mutually exclusive, with enough S and Sp to support the diagnosis.
Keywords: uveitis-clinical/animal model • inflammation • bacterial disease