Diagnosis of tuberculous uveitis: clinical application of an interferon-gamma release assay

To determine the role of the QuantiFERON-TB Gold In-Tube (QFT) (Cellestis Inc., Carnegie, Australia) assay in the diagnosis of tuberculosis (TB) uveitis.

Retrospective cohort study.

The study included 157 patients with suspected TB uveitis seen over an 18-month period (August 1, 2006, to February 31, 2007) at the Singapore National Eye Center (SNEC) uveitis clinic.

We identified all cases of suspected TB uveitis in the above-mentioned time period and reviewed all medical records of the cases. Clinical findings, type of treatment instituted, response to treatment, and results of investigations such as QFT, tuberculin skin test (TST), and chest x-rays were recorded. A novel method of using treatment response to determine the presumed diagnosis of TB was used to estimate the accuracy of QFT and TST.

The positive likelihood ratio (LR+), negative likelihood ratio (LR-), and area under the receiver operator characteristic curve (ROC) of the investigations were estimated.

QFT is not superior to the TST in sensitivity as a screening test or first-line study in TB-related uveitis; however, QFT is more specific than the TST in identifying infections by Mycobacterium tuberculosis. Negative QFT tests should be interpreted with caution, because they do not exclude the diagnosis.

The new QFT is only slightly superior to the TST in the diagnosis of TB uveitis. Thus, there is an important role for interpreting the QFT together with the TST. This is the first and largest study of its kind to evaluate the use of QFT in the clinical diagnosis of TB uveitis.