RetINal Toxicity And HydroxyChloroquine Therapy (INTACT): protocol for a prospective population-based cohort study

Area of Science:

• Ophthalmology
• Rheumatology
• Pharmacovigilance

Background:

• Hydroxychloroquine (HCQ) is a crucial medication for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
• Concerns regarding HCQ-induced retinal toxicity are increasing, necessitating updated risk assessments.
• Current guidelines recommend revised screening protocols for HCQ users.

Purpose of the Study:

• To re-evaluate the incidence rate of hydroxychloroquine (HCQ) retinal toxicity.
• To identify key risk factors associated with HCQ retinopathy.
• To describe the clinical course and progression of retinal toxicity after HCQ discontinuation.

Main Methods:

• Prospective, population-based cohort study of 5508 adult SLE and RA patients in British Columbia, Canada, on HCQ for ≥5 years.
• Annual/biannual retinal screening using spectral domain-optical coherence tomography (SD-OCT) over 5 years, following American Academy of Ophthalmology guidelines.
• Standardized imaging, diagnosis, and severity staging by masked reviewers; incidence calculated with competing risk of death; hazard ratios for risk factors determined.

Main Results:

• The study is designed to calculate the incidence of HCQ retinal toxicity.
• It will identify and quantify risk factors for HCQ retinopathy.
• The progression of retinal toxicity over a 5-year period will be estimated.

Conclusions:

• This research will provide updated data on HCQ retinal toxicity incidence and risk factors.
• Findings will inform clinical practice regarding HCQ monitoring in rheumatic diseases.
• Understanding the progression of toxicity is crucial for patient management and long-term outcomes.