To ascertain the false positive rate of red Amsler grid screening in an outpatient rheumatologic setting.
Red Amsler grid screening was performed on 170 consecutive patients presenting with rheumatoid arthritis or systemic lupus erythematosus. Patients with abnormal screening results were referred for ophthalmologic evaluation and formal visual field testing.
Nineteen patients identified scotomata on red Amsler grid. Despite numerous recall attempts, only 9 of the 19 patients with scotomata presented for ophthalmologic evaluation. The positive predictive value was 5-58%. Roughly 6-11% of all patients screened had a false positive screening test.
While red Amsler grid screening may allow rheumatologists to identify patients who are more likely to have hydroxychloroquine ocular toxicity, an abnormal red Amsler grid screening is in itself an unreliable predictor of toxicity.