A Retrospective, Longitudinal Study to Evaluate Healing Lower Extremity Wounds in Patients with Diabetes Mellitus and Ischemia Using Standard Protocols of Care and Platelet-Rich Plasma Gel in a Japanese Wound Care Program
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Thirty-three of the 40 wounds (83%) healed completely in an average of 145.2 days (SD: 21.29), which was statistically significant (P = .00002). Mean changes over time in area (P = 5.0 x 10-7), depth (P = 1.2 x 10-6), and volume (P = 7.3 x 10-5) were all statistically significant (see Figure 1). The mean number of PRP gel treatments was 6.1 (SD: 3.88; median: 5; range: one to 17). Of the 24 DM/ASO wounds, 19 (79%) healed during an average of 108.1 days (SD: 107.2). Figures 2 through 5 show typical treatment outcomes seen during the study.
Of the seven individuals who did not heal, two died (due to non study-related comorbidities), two terminated treatment, two transferred out of treatment/clinic, and one underwent amputation.
Survival distributions (time to healing) between the run-in and treatment time periods were significantly different (Mantel-Cox Log rank, P = 0.00002) (see Figure 6).
Cox regression analysis of time to healing showed that smoking (Yes or No) and other comorbidities were highly correlated values with other variables within the correlation matrix. Inclusion of these variables also led to unstable beta coefficients with very high ORs. Their removal tended to stabilize any model. Consequently, they were not included in model refinement. Three factors (hypertension, revascularization, and number of PRP gel treatments) had marginally significant time dependence but were not modeled with respect to time as plots showed that these issues were caused by the relatively small sample numbers in one of the levels of the factors. The final regression model had two covariates and four factors with a –2 log likelihood of 136.67, chi square = 47.54, P = 4.4 x 10-8 (see Table 2).
Use of ORs for variables determined the odds of healing to occur. The OR for area at first visit for PRP application (T2) was 0.429, meaning that for every increase in an order of magnitude of area, the odds of healing diminish by 0.429 (see Table 2). Likewise, the OR for age of wound at T2 was 0.106, meaning that for every increase in an order of magnitude of time, the odds of healing decrease by 0.106. Having hypertension diminished the odds of healing by 0.005, but having revascularization increased the odds of healing by 5.02, meaning that a prior revascularization procedure increases the odds of healing. An increase in the number of PRP gel treatments decreased the odds of healing (OR = 0.499 [four to eight treatments] and 0.060 [fewer than eight treatments]); this corroborates the data that showed wounds that received more treatments had an increase in severity and had more comorbidities. The OR for severe infection level/Wagner grade IV compared to an infection level of moderate/Wagner grade III was 14.62, which means that the odds of healing were increased by 14.62 when moderate infection level/Wagner grade III wounds were used a reference.
An independent t-test was performed on the percent change in wound area at 4 weeks for healed and unhealed wounds to determine the predictive value for complete healing. The percent change in wound area at 4 weeks for healed wounds was 62.3% (SD: 44.41) and 10.1% (SD: 37.76) for nonhealed wounds (P = 0.006).