Association between tissue loss type and amputation risk among Medicare patients with concomitant diabetes and peripheral arterial disease.
Academic Article
Overview
abstract
OBJECTIVE: Prior studies have described risk factors associated with amputation in patients with concomitant diabetes and peripheral arterial disease(DM/PAD). However, the association between the severity and extent of tissue loss type and amputation risk remains less well-described. We aimed to quantify the role of different tissue loss types in amputation risk among patients with DM/PAD, in the context of demographic, preventive, and socioeconomic factors. METHODS: Applying ICD-9 and ICD-10 codes to Medicare claims data(2007-2019), we identified all patients with continuous fee-for-service Medicare coverage diagnosed with DM/PAD. Eight tissue loss categories were established using ICD-9 and ICD-10 diagnosis codes, ranging from lymphadenitis(least severe) to gangrene(most severe). We created a Cox proportional hazards model to quantify associations between tissue loss type and one- and five-year amputation risk, adjusting for age, race/ethnicity, sex, rurality, income, comorbidities, and preventive factors. Regional variation in DM/PAD rates and risk-adjusted amputation rates was examined at the hospital referral region(HRR) level. RESULTS: We identified 12,257,174 patients with DM/PAD(48% male, 76% White, 10% prior myocardial infarction, 30% chronic kidney disease). While 2.2 million patients(18%) had some form of tissue loss, 10.0 million patients(82%) did not. The one-year crude amputation rate(major and minor) was 6.4% in patients with tissue loss, and 0.4% in patients without tissue loss. Among patients with tissue loss, one-year any amputation rate varied from 0.89% for patients with lymphadenitis to 26% for patients with gangrene. One-year amputation risk varied from two-fold for patients with lymphadenitis(aHR 1.96, 95%CI 1.43-2.69) to 29-fold for patients with gangrene(aHR 28.7, 95%CI 28.1-29.3), compared to patients without tissue loss. No other demographic variable including age, sex, race, or region incurred a hazard ratio for one- or five-year amputation risk higher than the least severe tissue loss category. Results were similar across minor and major amputation, and one- and five-year amputation outcomes. At a regional level, higher DM/PAD rates were inversely correlated with risk-adjusted five-year amputation rates(R2=0.43). CONCLUSION: Among 12 million patients with DM/PAD, the most significant predictor of amputation was presence and extent of tissue loss, with an association greater in effect size than any other factor studied. Tissue loss could be used in awareness campaigns as a simple marker of high-risk patients. Patients with any type of tissue loss require expedited wound care, revascularization as appropriate, and infection management to avoid amputation. Establishing systems of care to provide these interventions in regions with high amputation rates may prove beneficial for these populations.
