Prognosis of the infected diabetic foot ulcer: a 12-month prospective observational study

Abstract

Aims: To determine clinical outcomes and explore prognostic factors related to ulcer healing in people with a clinically infected diabetic foot ulcer.

Methods: This multicentre, prospective, observational study reviewed participants' data at 12 months after culture of a diabetic foot ulcer requiring antibiotic therapy. From participants' notes, we obtained information on the incidence of wound healing, ulcer recurrence, lower extremity amputation, lower extremity revascularization and death. We estimated the cumulative incidence of healing at 6 and 12 months, adjusted for lower extremity amputation and death using a competing risk analysis, and explored the relationship between baseline factors and healing incidence.

Results: In the first year after culture of the index ulcer, 45/299 participants (15.1%) had died. The ulcer had healed in 136 participants (45.5%), but recurred in 13 (9.6%). An ipsilateral lower extremity amputation was recorded in 52 (17.4%) and revascularization surgery in 18 participants (6.0%). Participants with an ulcer present for ~2 months or more had a lower incidence of healing (hazard ratio 0.55, 95% CI 0.39 to 0.77), as did those with a PEDIS (perfusion, extent, depth, infection, sensation) perfusion grade of ≥2 (hazard ratio 0.37, 95% CI 0.25 to 0.55). Participants with a single ulcer on their index foot had a higher incidence of healing than those with multiple ulcers (hazard ratio 1.90, 95% CI 1.18 to 3.06).

Conclusions: Clinical outcomes at 12 months for people with an infected diabetic foot ulcer are generally poor. Our data confirm the adverse prognostic effect of limb ischaemia, longer ulcer duration and the presence of multiple ulcers.

Figure 1

Participant flow diagram. *Other reasons for exclusion: consent was not attained for unknown reasons (11 participants); lacked capacity to consent (2 participants); provided incomplete consent (1 participant); declined to consent (1 participant); consented but case note review not completed (1 participant).

Figure 2

Healing estimates and cumulative incidence functions of the time to healing in the presence of competing risks of death or amputation. *This refers to the number of participants left in the ‘risk’ set consisting of those uncensored without an event (healing, death, or amputation).