Lymphopaenia a Noninvasive and Useful Biomarker for Diagnosing Ocular Sarcoidosis, Study Suggests

Low levels of white blood cells in the blood — a condition known as lymphopaenia — could be a useful, noninvasive biomarker for the diagnosis of ocular sarcoidosis, a study reports.

The study, “Lymphopaenia as a predictor of sarcoidosis in patients with a first episode of uveitis,” was published in the British Journal of Ophthalmology.

Ocular sarcoidosis is a type of sarcoidosis that causes inflammation, swelling, and destruction of eye tissues, a set of symptoms that fall under the general term uveitis. Diagnosis usually involves a biopsy of the affected tissues. However, this procedure is highly invasive and difficult in patients with uveitis suspected to be ocular sarcoidosis.

For this reason, other noninvasive diagnostic techniques, such as chest X-rays and serum biomarkers, are highly sought after.

“However, these tests have limited positive predictive values,” according to the researchers, meaning that sometimes these tests fail to identify true cases of ocular sarcoidosis, which is far from ideal.

In sarcoidosis, white blood cells (lymphocytes) tend to leave blood vessels and start accumulating inside affected tissues, leading to lymphopaenia. For this reason, previous studies have proposed the inclusion of lymphopaenia in the diagnostic criteria of sarcoidosis. However, no study so far has validated its use as a diagnostic biomarker.

Researchers from the Erasmus University Medical Center in the Netherlands have now investigated the potential of using lymphopaenia as a diagnostic tool for sarcoidosis-associated uveitis.

The retrospective study enrolled 191 patients who had experienced their first uveitis episode, but had not received a confirmed diagnosis of sarcoidosis at the beginning of the study.

Out of these patients, 32 (17%) were diagnosed with sarcoidosis-associated-uveitis based on data from biopsies and X-rays. Lymphopaenia was found in 61 patients (32%), of whom 24 (39%) also had confirmed sarcoidosis.

Lymphopaenia was observed more often among patients with sarcoidosis-associated uveitis (75%) than in those who had uveitis not linked to sarcoidosis (23%). In addition, researchers found that when corrected for sex, race, and age at onset of uveitis, the presence of lymphopaenia in a patient correlated with a 12 times higher risk of sarcoidosis.

Further tests also demonstrated that lymphopaenia had a sensitivity of 75% and a specificity of 77% in identifying patients with sarcoidosis-associated uveitis.

“In conclusion, lymphopaenia appears an useful diagnostic biomarker for the diagnosis of sarcoidosis in patients experiencing their first uveitis attack,” the researchers wrote.

“Further avenues of research should concentrate on the development of other non-invasive tests for the diagnosis of ocular sarcoidosis and selecting the optimal combination of available tests,” they added.