Background/Purpose: Hydroxychloroquine (HCQ) retinopathy after 10 years or more of use is more frequent than previously appreciated. This led to new ophthalmology guidelines that changed the recommended dosing from 6.5 mg/kg to 5 mg/kg. However, it is not clear that the lower dose of hydroxychloroquine will have the same efficacy for SLE activity or the same protective role against cardiovascular risk factors and thrombosis. We asked whether hydroxychloroquine blood levels could help identify those at greater future risk of retinopathy.

Methods: We analyzed data on 477 SLE patients from a clinical cohort who had repeated assessments of HCQ blood concentrations, and were evaluated one or more times for retinopathy (306 single retinopathy exam, 115 two and 58 three or more assessments). The patients were 93% female and 42% Caucasian. Hydroxychloroquine blood levels were performed as previously described. In our analysis, HCQ toxicity was defined dichotomously by a retina expert: all those with a value of “No” or “Possible” were categorized as not having HCQ toxicity, and those who had a “Yes” were categorized as having it. Mean and maximum HCQ blood concentration over all cohort visits prior to the final retinopathy assessment were calculated. Risk of HCQ toxicity was then assessed in tertiles defined by these variables. The duration of hydroxychloroquine use (years in tertiles by distribution) and its association with HCQ toxicity were also examined.

Results: The risk of HCQ toxicity is shown in Table 1.

Table 1. Risk of HCQ retinal toxicity by variable.

Patients had a variety of retinal testing done, with optical coherence testing most frequent. Table 2 shows the concordance of a test abnormality with the retina expert opinion.

Table 2 – Performance of retinal imaging modalities relative to expert diagnosis

OCT Sensitivity = 85%, Specificity = 92%

ERG Sensitivity = 100%; Specificity = 60%

MP1 Sensitivity = 100%; Specificity = 76%

FAF Sensitivity = 76%; Specificity = 76%

Conclusion: Our data show that the risk of HCQ retinopathy increases in men, Caucasians, older patients and with duration (but the frequency was less than in other publications). For the first time, out data show the utility of HCQ blood levels in predicting retinopathy. This would allow clinicians to either decrease dose or increase monitoring in those with high blood levels. Our data also show the need for ophthalmologists with retinopathy expertise to interpret retina testing, as screening tests can be abnormal due to causes other than HCQ retinopathy. Stopping HCQ based on an abnormal test without confirmation from a retinopathy expert could needlessly deprive an SLE patient of an important medication.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/hydroxychloroquine-blood-levels-show-significant-trend-test-for-risk-of-retinopathy/