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


Wounds. 2012;24(1) 

In This Article



A 5-year slice of data, March 2005 – July 2010, was selected in order to evaluate the effect of time on outpatient resource utilization. The Intellicure electronic health record (EHR) is certified by the ONC (Office of the National Coordinator) of Health Information Technology as a complete ambulatory care electronic health record in accordance with the certification criteria adopted by the Secretary of Health and Human Services (HHS). More than 200 elements of staff work contribute to the facility acuity scoring system which has been separately published and validated (https://www.intellicure.com/Index/Product_iFAST.aspx).[13] In addition, a "wound care-specific" physician-billing module using the 1997 Center for Medicare and Medicaid Services (CMS) evaluation and Management (E/M) documentation guidelines was developed, which automatically audits the chart using a computer algorithm and then internally calculates the physician charges, including all procedural documentation for interventions, such as debridements or the application of bioengineered skin. The clinician does not "select" the level of service at the completion of the visit. Rather, the EHR informs the clinician of the level of service that is supported by the documentation contained within the chart at the completion of the visit. Thus, compliance between documentation and billed level of service for both the facility and the physician are ensured. Computers are present in every room allowing "point of service" documentation of all aspects of the patient's care in a prospective fashion. All dressing products are selected from menu options based on facility formulary, and the software generates interval dressing orders to home nursing agencies.

Data are maintained on servers hosted by the vendor, accessed through a secure portal using remote desktop protocols. Clinics agree to participate in the US Wound Registry from which facilities receive benchmarking reports for the purpose of quality assurance. There is a well-defined vetting process before clinics can contribute to the Registry. Data must meet specific standards for completeness. After 3 days of intensive onsite training prior to initial "go live," clinics undergo remote chart audits with telemedicine for 6 weeks. For 6 months, charting undergoes a data integrity review process before the site can begin to contribute to the Registry. Periodic chart audits continue and if facilities fail to meet quality standards, contribution to the registry is halted until quality standards are met. Through the registry, de-identified, cumulative data can be evaluated from all centers. While registry information is collected primarily for quality improvement (QI) activities, it can be used for research. The boundary between these two types of activities can be indistinct because they often serve both functions simultaneously. Studies involving human subjects may be exempt from IRB review if the research involves the study of existing data.[14] Furthermore, de-identified data are not protected health information (PHI) and are not subject to the privacy rule if all elements that could be used to identify the individual have been removed. Thus, with the permission of the participating centers, EHR data are HIPAA de-identified and submitted to the US Wound Registry. For this project, 59 hospital-based outpatient wound centers in 18 states using the Intellicure electronic health record (EHR) provided data. While CMS defines "wounds" and "ulcers" as different entities, since a generic term encompassing both does not exist, unless otherwise specified, the authors will use the term "wounds" in this manuscript to indicate all types of chronic wounds and ulcers.

We had access only to outpatient data, so cost information from interval hospitalizations were not available. Furthermore, we did not attempt to include the cost of diagnostic testing (eg, angiograms, bone scans). Elements of cost included the billed advanced practitioner fee for the day's visit; the billed facility fee for the day's visit; billed procedure costs that day (eg, bio-engineered skin application, debridement, compression bandaging); the estimated cost of all interval dressings (based on the frequency of dressings ordered until the next visit) if the patients were performing their own dressing changes; the estimated charges for negative pressure wound therapy (based on an average daily rate, multiplied by the days for which NPWT was documented in the chart); and the billed number of hyperbaric oxygen therapy treatments. When patients received home nursing care, we estimated the cost of this on a daily rate or that specified by the CMS Home Health Prospective Payment System, and assumed this cost included the cost of the applied dressings. This method underestimates the total cost of NPWT and home nursing due to the "billing cycles" used for these services, as addressed more fully in the Discussion. Thus, while most of the costs were actual charges, some were estimated from orders contained within corresponding charts.

Dataset Preparation

Within the 5-year data slice, the initial registry database consisted of 11,664 patients. Since the goal was to assess both outcomes and resource utilization, 759 patients who underwent a consultation only and 1352 patients who were lost to follow-up were excluded. In addition, 484 patients who had no wound (eg, those seen for edema or lymphedema) were deleted, leaving 9069 patients. The data format was then converted from Microsoft SQL Server to PASW 19 (SPSS, Inc., Chicago, IL). Two cases were then found with patient age but no other data, such as wound measurements or assigned outcome. Data for 15 other patients were deleted because of miscoded data pertaining, for example, to body mass index (BMI).

At the wound level of data, some missing data were imputed as follows: 1619 wounds not associated with NPWT, and 451 wounds which were associated with NPWT had no initial tissue depth described at the base of the wound. These missing data were imputed using a maximum likelihood algorithm based on A) maximum depth of tissue exposed at any visit, and/or B) initial depth of wound. The 1204 wounds with incomplete ICD-9 coding were removed, along with 6001 wounds associated with NPWT in which it was too difficult to impute the missing data, leaving 11,740 wounds among the 9069 patients before conversion to PASW 19.

Sixty-one wounds were found with NPWT-type data attached but not coded as having had NPWT; these were recoded to the NPWT category. Forty-eight NPWT cases were found with no associated type of NPWT and were recoded to no NPWT. The following issues also resulted in exclusion of some cases or data: 1) the type of tissue at the wound bed was not recorded at the final visit (5842 values deleted); 2) 12 unknown values for maximum wound surface area were converted to missing values; 3) 175 cases with initial depth of < 0.1 cm were deleted; 4) 2311 cases with an initial wound surface area between 0 and 1 cm2 were also deleted, leaving 9254 wounds to be analyzed. During the merging of patient variables with wound variables, 1775 cases did not have matching keys, (a wound case had been deleted and thus could not be matched to patient variables or vice versa), which resulted in the deletion of 1775 wounds, leaving 7459 wounds in the merged dataset.

Using a boxplot for initial area and initial depth, 6 and 19 unique wounds, respectively, were identified as having exceptionally high values and these cases were deleted after effect on primary wound characteristics had been ascertained (area > 400 cm2 and depth > 9 cm). In addition, 49 cases had no NPWT duration for wounds treated with NPWT (these cases were deleted), and 293 cases had 0–4 days for duration of NPWT treatment (these cases were deleted), leaving 7099 wounds in 5240 patients to be analyzed.


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