Predicting Patient Outcome

Dear Readers: What if your patients could tell you whether or not they would respond to your current wound therapy by healing? Would you listen? How would you use this information? A growing body of information suggests that patients are telling us they are likely or unlikely to heal, and we are learning how to listen to their messages. Below are two recent articles that illustrate two different ways of “listening” to your patients to identify diabetic foot ulcers at risk of nonhealing and those likely to heal during 12 weeks of care. As you read them, ask yourself, “What would I do differently to diagnose and remove the cause of tissue deterioration for a patient at risk of nonhealing? How could I use this information to improve my patients’ outcomes?” Does this predictability extend to other kinds of wounds? The beginnings of answers are in the evidence you are about to read. Laura L. Bolton, PhD Department Editor Percent Change in Diabetic Foot Ulcer Area Over Four Weeks of Care Predicts 12-Week Healing Reference: Sheehan P, Jones P, Caselli A, Giurini J, Veves A. Percent change in wound area of diabetic foot ulcers over a 4-week period is a robust predictor of complete healing in a 12-week prospective trial. Diabetes Care 2003;26(6):1879–82. Rationale: Foot ulcers in patients with diabetes that do not heal expediently are believed more likely to become infected, to cause patient hospitalization, and to be amputated, resulting in less acceptable outcomes with increased costs. Objective: This study assessed the capacity of diabetic foot ulcer four-week healing rates to predict complete healing over a 12-week period. Methods: Wound area measurements were made on enrollment and after four weeks of care on 203 patients among 276 enrolled with Wagner Grade I-II diabetic foot ulcers at least 1cm2 in area and of at least 30-days duration. All foot ulcers were uncomplicated by infection or ischemia and randomized to receive 12 weeks treatment with either moist saline gauze or a collagen/oxidized regenerated cellulose dressing in conjunction with treatment recommended by the Consensus Development Conference on Diabetic Foot Wound Care.[1] Results: Patients whose ulcers healed at 12 weeks had a mean four-week percentage reduction in area of 82 percent as compared with 25 percent for those unhealed at 12 weeks (pConclusions: If uncomplicated Wagner Grade I-II diabetic foot ulcers fail to decrease in size to half of their original area during the first four weeks of care, there is a high likelihood that they will not heal during 12 weeks of care using the current protocol. Debridement Performance Index as a Predictor of Diabetic Foot Ulcer Healing Reference: Saap L, Falanga V. Debridement performance index and its correlation with complete closure of diabetic foot ulcers. Wound Repair Regen 2002;10:354–9. Rationale: Debridement has long been considered standard care in diabetic foot ulcers and has been correlated with wound closure, yet the predictive validity of wound debridement has not been proved owing largely to lack of a standardized measure of adequacy or extent of debridement. Objective: This prospective cohort study measured the predictive validity for healing outcomes of a new system to score the extent of diabetic foot ulcer debridement relative to wound need, called the Debridement Performance Index (DPI). Methods: The DPI score ranges from 0 to 6. It is the sum of the following scores: 0 if debridement was needed but not done; 1 if it was needed and done; and 2 if it was not needed for each of the following three types of tissue: (a) callus, (b) skin undermining, and (c) wound bed necrotic tissue. Observers blinded to treatment evaluated the DPI of full-thickness neuropathic diabetic foot ulcers on 143 patients based on digital ulcer photographs taken before and after debridement. All patients had been enrolled in a multicenter randomized controlled study comparing healing outcomes for noninfected, nonischemic ulcers dressed with standard therapy versus those dressed with a Biologic Skin Construct. Correlations and logistic regression evaluated the degree of association between DPI and complete wound closure after 12 weeks of care. Results: There was a significant association between DPI score and complete wound closure after 12 weeks on the protocol (p=0.03), with lower DPI scores associated with lower incidence of complete 12-week wound closure. Patients whose ulcer DPI scores were 3 to 6 were 2.4 times more likely to achieve complete closure during 12 weeks than those with DPI scores 0 to 1, an effect independent of the treatments compared in the study. Ulcer DPI scores of 3 to 6 correctly predicted complete 12-week healing 55 percent of the time (positive predictive value). DPI score 0 to 2 correctly predicted 12-week nonhealing in 65.5 percent of the ulcers (negative predictive value). From Table 2 of this reference one can also calculate the sensitivity of the DPI score as the percent of healed ulcers correctly diagnosed by DPI score 3 to 6 = 63/73 or 86.3 percent. Similarly, its specificity is the percent of ulcers nonhealed at 12 weeks correctly diagnosed by DPI scores of 0 to 2 = 19/70 or 27.1 percent. Conclusions: The authors conclude that the DPI may be useful in standardizing debridement interventions and in reminding clinicians of the need for thorough debridement. Clinical Perspective Of the two measures, four-week percentage wound area reduction appears to have the greater diagnostic and predictive value in differentiating healing from nonhealing diabetic foot ulcer patients. Does this predictability extend to other kinds of wounds? Recent literature suggests that at least 39-percent reduction in ulcer area during the first two weeks of care predicts more expedient healing of full-thickness pressure ulcers[2] while at least a 30-percent reduction in two-week wound area serves the same function in full-thickness venous ulcers.[3] The prognostic value of three-week[4] and four-week[5] percentage change in wound area for up to 24-week[5] healing outcomes has also been confirmed more generally in venous ulcers. Simple measurements of the wound’s longest length x width to estimate percent wound reduction in area[6] during 2 to 4 weeks of care is an effort well spent, enabling clinical professionals to heed and respond appropriately to nature’s early warning that the patient’s wound is not progressing toward healing.