Wound Care Outcomes and Associated Cost Among Patients Treated in US Outpatient Wound Centers

Data From the US Wound Registry

Caroline E. Fife, MD, CWS; Marissa J. Carter, PhD, MA; David Walker, CHT; Brett Thomson, BS

Disclosures

Wounds. 2012;24(1) 

In This Article

Results

In the prepared dataset the 5240 patients exhibited 7099 wounds for an average of 1.3 wounds per patient. These patients made 119,786 visits over the time 5-year time frame, a mean of 16.8 visits per wound, but the range was very large (1–374). The mean patient age was 61.7 years (standard deviation [SD]: 17.42; range 19–103 years) with 52.3% of the dataset being male, 47.7% female. The preponderance of patients were Caucasian (73.1%) with Hispanics representing 10.7%, African-Americans 9.3%, and other races 1.7%. As might be expected from the age data, the majority of patients were Medicare beneficiaries (52.6%), with healthcare coverage for the remainder provided by private insurance in 36.2%, Medicaid in 3.2%, and worker's compensation or self pay in 8.0%. These 5240 patients accrued a total "cost to the system" of $29,249,500 for their outpatient care.

The average number of serious comorbid conditions per patient was 1.8 (range 0–9). The most common serious comorbid condition was diabetes, present in 46.8% of patients (including 33.1% of patients who had ulcers not identified as diabetic foot ulcers). A surprising 71.3% of patients were classified as obese or overweight (BMI > 25), and 51.3% had diagnoses indicating cardiovascular or peripheral vascular disease. Of note, 7.5% of patients were on dialysis or had undergone renal transplantation, and 8.5% of patients were taking prednisone, a drug likely to inhibit normal healing processes.

The distribution of wound and ulcer types is depicted in Figure 1. Nonhealing surgical wounds represent the largest category at 20.8% of the total, followed by pressure ulcers on the body (eg, sacrum, trochanter, ischium) at 19.2%. Pressure ulcers on the heels represented 3.8% of the total dataset, with these data being maintained separately due to their association with peripheral vascular disease. Diabetic foot ulcers were the next most common ulcer type at 13.7% of the total, followed by traumatic wounds or chronic ulcers which are not otherwise classified (12.8% and 12.1%, respectively). These traumatic wounds were often associated with diabetes or vascular disease, and the generic "chronic ulcers" were often due to sickle cell anemia, scleroderma, vasculitis, or other disease states, but the ICD-9 classification system does not allow providers to identify ulcers as being caused by these diseases so they remain in a nonspecific class. Venous ulcers represented 7.8% of the dataset, and arterial ulcers and nonhealing amputations 1.5% each.

Figure 1.

Distribution of wound types.

Almost two-thirds of wounds (65.8%) had an "outcome" of "healed" or the measurements in the chart indicated that the wound was no longer present at the final visit. The average time to heal in those wounds that healed was 15 weeks (107 days; SD: 150.29) but the range was very large (< 1 week to 5 years) with 10% of wounds taking 33 weeks or more to heal. The average wound surface area was 19.5 cm2 (SD: 39.71; range: 1–480 cm2). An outcome of "amputated" was found for 1.38% of wounds (highest for diabetic foot ulcers at 6.4%, but also high for arterial ulcers at 4.0%), leaving 31.2% of wounds whose benefit from treatment was unclear despite considerable resource utilization. Of note, 1.63% of patients died in service or within 4 weeks of the last visit.

Half of the wounds that healed did so with only the use of moist wound care (50.8%) and without the need for advanced therapeutics (AT) defined as hyperbaric oxygen therapy (HBOT), bioengineered skin (eg, Apligraf or Dermagraft), or negative pressure wound therapy (almost exclusively provided in this dataset by the V.A.C.®, KCI, San Antonio, TX). Moist wound care in these clinics consisted of a variety of sophisticated dressing products (eg, alginates, hydrocolloids, hydrofibers, antimicrobial and collagen-containing dressings), but these were not considered "advanced" wound care. However, when advanced therapeutics were utilized, they represented significant cost drivers since these interventions are relatively expensive with 19.7% of patients receiving HBOT, 34.4% receiving NPWT, and 5.3% receiving bioengineered skin; the corresponding percentages of wounds receiving these advanced therapeutics were 21.9% with HBOT, 31.0% with NPWT, and 5.9% with bioengineered skin.

The distribution of major cost drivers for healed wounds is depicted in Figure 2. Although hyperbaric oxygen therapy charges and bioengineered skin are both usually billed as part of hospital-based outpatient wound center charges, we have separated them here in order to visualize how these advanced therapeutics contribute to outpatient costs. We see that one of the most significant cost contributors is home nursing (18.4% of total cost) because so many patients are unable to perform self-care. These costs were estimated based on the weeks over which orders for home health appeared in the chart and the frequency of visits ordered. Physician charges represent 12.5% of resource utilization, with dressings at only 7.7%. In this dataset, bioengineered skin ("Bioskin" in the graph) also represented a relatively small percentage of resource utilization (less than 6% of total charges).

Figure 2.

Breakdown of cost to heal by various factors.

There were wide variations in resource utilization among wounds which healed when analyzed by wound type. The average cost to heal per wound was $3927. Jeopardized flaps and grafts were the most expensive wound type with a mean cost to heal per wound of $9358. Diabetic foot ulcers were the most expensive type of chronic ulcer and were twice as expensive as other types with an average cost per patient of $5391. The average cost per wound for pressure ulcers was $3349.

The final General Linear Model predicted a significant portion of the variance in wound healing outcomes, with an r2 = 0.348, and an overall model P value of < .0001. However, there was a significant limitation in the model due to violation of Levene's test of equality of error variances, meaning that the variance between groups for several factors was significantly different. Significant factors that increased cost to heal included the presence of diabetes (P = .007), the need for systemic antibiotics (P = .003), renal failure (particularly if prescription narcotic pain medication was required; P = .028), immunocompromise (eg, use of prednisone or medications associated with organ transplantation; P = .02), and current smoking (P = .02). When patients had 0 or 1 comorbidity the cost to heal the wound was significantly less than when they had 2 comorbidities (mean: $3601 vs $4282; [SD: 5226.96 and 5727.59]; P = .000024).

For those wounds that did not heal, the average time in service was 16 weeks. This suggests that the majority of patients who failed to achieve healing did not continue to be followed in the outpatient wound center. However, 10% of patients who failed to heal were still being followed at 39 weeks. Among patients followed for long periods, the cost of care increased as treatment duration lengthened. Figure 3 shows the cumulative cost of care in relation to years in treatment where these data were available. Although 2-year data were available in only 30 patients, the cost of care per patient was more than $18,000.

Figure 3.

Cost of unhealed wounds increases with longer length of time in service. Numbers in boxes represent number of wounds for each column. P values for difference between means: 0–0.5 years and 0.51–1.0 years: < .0001; 0–0.5 years and 1.01–2.0 years: < .0001; 0–0.5 years and ≥ 2.0 years: .005; 0.51–1.0 years and 1.01–2.0 years: .022; 0.51–1.0 years and ≥ 2.0 years: .045; 1.01–2.0 years and ≥ 2.0 years: .291.

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