Loss to Follow-Up in Intermediate AMD Patients Enrolled in the University of Colorado Age-Related Macular Degeneration Registry

Abstract

Purpose : The purpose of the Colorado AMD registry (started in 2014) was to study systemic and imaging biomarkers of AMD progression using an annual blood draw with multimodal imaging. A concern in every cohort study is loss to follow-up (LTFU), an event known to impact the validity of results in studies. This abstract discusses the methods utilized to minimize LTFU among patients with the intermediate form of AMD (iAMD) and present the cohort’s attrition rate.

Methods : A review of the iAMD cohort is completed every 6 months (most recently May 2023). 5 patient groups are identified (Table 1): Group 1: Active follow-up with visits to our retina clinic; Group 2: Patients who are followed using only the Electronic Medical Record (EMR) with no in-person research visits due to declining health, move to a satellite clinic, or by patient request; Group 3: Complete LTFU - patients withdrawn after enrollment, moved out of state or to another practice; Group 4: Deceased patients; Group 5: Potential LTFU; patients not seen at the retina clinic in the past year with no appointment scheduled.

To address potential LTFU, Group 5 patients received a recall letter and phone call to inform the patient that they need an appointment. Three months after this intervention, another review of group 5 was conducted. The status of Group 5 was updated into Group 5a: appointment made after intervention or Group 5b: no appointment made after intervention. The number of person years contributed by each patient was calculated using the date of enrollment and the date of the last appointment with retina.

Results : The results of the review from May 2023 are shown in Fig 1. 449 patients with iAMD were reviewed. 47 (54.0%) of Group 5a made an appointment within 3 months following the intervention and 40 (46.0%) did not respond to the intervention (Group 5b). Group 5b continues to be monitored for appointments during each 6-month review. The numbers of patient years of follow up are shown in Table 1. Despite some LTFU, these patients contributed data with an average follow-up time of 2.9 years for patients who responded to the intervention, and 1.7 years for patients who did not.

Conclusions : These findings provide estimates of the rate of attrition in an iAMD cohort and demonstrate the importance of ongoing vigilance and review of aging patients in AMD cohorts to minimize the number of patients LTFU.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.