Recurrence rates suggest delayed identification of plantar ulceration for patients in diabetic foot remission

Introduction Foot ulcers are a common and costly complication of diabetes, and delays in treatment can result in impaired healing, infection, hospitalization, and lower extremity amputation. Research design and methods We aimed to determine whether patterns in plantar diabetic foot ulcer (DFU) recurrence coincided with typical intervals between routine preventive care appointments, which would suggest that delays exist between ulcer development and identification. We completed an analysis of existing data from two multicenter studies in 300 total participants. We analyzed unadjusted counts of DFU binned in weekly intervals and defined 'exam periods' as intervals from 2 to 4 weeks, from 6 to 8 weeks, within 1 week of 3 months and within 1 week of 6 months. We tested whether recurrence rates during exam periods were equivalent to rates outside exam periods. We estimated the delay between DFU development and DFU identification such that the rate of development would have been constant. Results During exam periods, a total of 43 DFUs were identified (43/86=50%) despite the fact that these periods represent only 23.5% of follow-up in aggregate. Accounting for censoring, the annualized incidence during exam periods was 0.68 DFU/year (CI 0.48 to 0.89) in contrast to 0.25 DFU/year (CI 0.18 to 0.32) outside exam periods (incidence ratio=2.8, CI 1.8 to 4.3). We estimated delays between DFU occurrence and identification to average 15.3 days (IQR 7.4-23.7 days). Conclusions These findings have potential implications for practice, particularly related to the value of telehealth and in-home monitoring of patients in diabetic foot remission. Additionally, there are implications for study design, which should consider the impact of interval censoring and attempt to control for confounders related to frequency and timing of exams.