Background <p>Guideline-concordant screenings for hydroxychloroquine retinopathy (HCQ-R) are essential for safe long-term use of HCQ. We assessed adherence to the HCQ-R screening recommendations among patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) and evaluated patient- and health system-level predictors of adherence.</p> Methods <p>We conducted a longitudinal population-based cohort study (1997–2023) using linked British Columbia administrative health data capturing all physician and hospital encounters, tests billed, pharmacy-dispensed medications, and demographics. Using previously published algorithms, we identified all adults with SLE or RA who initiated HCQ after diagnosis and remained on therapy continuously for ≥ 1 year. Guideline-concordant (valid) screening was defined as a retinal visit (ICD-9 362.xx) with spectral domain optical coherence tomography and/or visual field-testing fee(s) (22067/02043) within a ± 30-day window, from baseline (HCQ initiation) until 31-Dec-2023, HCQ cessation, or censoring. Population-level adherence was assessed based on baseline and annual rates of valid screening. Patient-level adherence was assessed as the mean cumulative count of valid screenings received by each year of follow-up, with 95% CIs. Predictors of annual valid screening, including physician-care patterns (continuous vs. noncontinuous rheumatology vs. family-physician care), health authority regions, socioeconomic status (SES) and baseline screening, were assessed via multivariable generalized estimating equations adjusted for demographics and comorbidities.</p> Results <p>Of the 28,301 eligible patients for screening, 24% completed a valid baseline screening within year 1; during years 2–25, the annual rate of valid screenings ranged from 20 to 35%, and 70% remained unscreened on average. By 15 years, patients received on average 2.7 (95% CI, 2.6–2.8) valid screenings compared with at least 12 expected by this time, as recommended by the guidelines. Having a baseline screening was the strongest predictor of subsequent annual screenings (adjusted odds ratio [aOR] 5.71; 95% CI: 4.89–6.67). Compared with continuous rheumatology care, family physician care had lower odds of screening (aOR, 0.59; 0.49–0.72). Most regions had lower screening rates than did Vancouver Coastal Health (9.50%-24.57%), with the lowest screening rate in Island Health (aOR, 0.39; 0.30–0.51). SES was not significantly associated with the odds of receiving annual screening.</p> Conclusions <p>Guideline-recommended HCQ-R screening adherence was consistently low within a publicly funded health-care system; on average, one-fourth of patients on long-term HCQ, completed a valid screening annually. Strategies to strengthen guideline-based practices and reduce regional disparities are needed.</p>