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An Instrument to Measure Healing in Pressure Ulcers

Development and Validation of the Pressure Ulcer Scale for Healing (PUSH)

^a School of Nursing, University of California–San Francisco
^b Plastic Surgery Research, University of Virginia Medical Center, Charlottesville
^c Division of Geriatrics, Saint Louis University, Missouri
^d College of Nursing, University of Iowa, Iowa City
^e University of Alabama–Birmingham
^f Sussman Physical Therapy, Inc., Torrance, California
^g University of California–Los Angeles
^h College of Nursing, University of Nebraska, Omaha
ⁱ Harper Hospital/Detroit Medical Center, Detroit, Michigan

Nancy A. Stotts, University of California–San Francisco, School of Nursing, 2 Koret Way, Room 631, Box 0610, San Francisco, CA 94143-0610 E-mail: nancy.stotts{at}nursing.ucsf.edu.

Decision Editor: John E. Morley, MB, BCh

	Abstract

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Background. Currently, there is no instrument that provides an accurate and simple method of monitoring pressure ulcer healing in clinical practice. This article reports the two studies that were conducted to assess the validity of the Pressure Ulcer Scale for Healing (PUSH) as a tool to monitor healing of stage II–IV pressure ulcers.

Methods. Subjects in both studies (N = 103 and N = 269) were elderly (mean Study 1, 75 years, mean Study 2, 80 years), and the majority were women (Study 1, 51%, Study 2, 70%). Study data were extracted from patients' permanent records.

Results. Principal components analysis confirmed that the PUSH tool accounted for 58% to 74% of the wound healing variance over a 10-week period in Study 1 and 40% to 57% of the wound healing variance over a 12-week period in Study 2. In addition, multiple regression analysis, used to measure the sensitivity of the model to total healing, showed PUSH accounted for 39% of the variance in 6 weeks and 31% of the variance over 12 weeks (p < .001; Studies 1 and 2, respectively).

Conclusions. Data from these two studies confirmed that the PUSH tool, with the components of length times width, exudate amount, and tissue type, is a valid and sensitive measure of pressure ulcer healing. It is a practical approach that provides clinically valid data regarding pressure ulcer healing. Further testing is needed to confirm these findings.

PRESSURE ulcers are common ^(1)(2)(3), costly (⁽⁴⁾,⁽⁵⁾), and associated with pain, suffering, and decreased quality of life ⁽⁶⁾. Moreover, pressure ulcers are extremely slow to heal. Measuring progress toward healing has been recommended to occur on a weekly basis ⁽⁷⁾. Currently, there is no instrument that provides a uniform, simple method of tracking pressure ulcer healing.

Data indicate that changes in ulcer size over a 2-week period are associated with the ulcer's likelihood of healing completely ⁽⁸⁾⁽⁹⁾. However, the change in size of an ulcer alone may not be a sufficiently sensitive indicator of progress toward healing. Other characteristics that are valid indicators of ulcer healing include the quantity or quality of exudate, presence of necrotic tissue, and an increase in the amount of granulation tissue ^(10)(11).

Measurement of progress in healing requires the wound be evaluated at more than one setting and that improvement or deterioration in wound status be identified. Although tools exist that allow for overall wound assessment ^(11)(12), no tool exists to track healing that is accurate, easy to use, and sensitive to change ⁽¹³⁾. Thus, the National Pressure Ulcer Advisory Panel developed the Pressure Ulcer Scale for Healing (PUSH) tool to track healing in stage II to IV pressure ulcers ⁽¹⁴⁾.

The PUSH tool consists of three parameters: length times width, exudate amount (none, light, moderate, and heavy), and tissue type (necrotic tissue, slough, granulation tissue, epithelial tissue, and closed). Each parameter is scored, and the sum of the three yields a total wound status score. Observation of the changes in the direction and magnitude of the score over time indicates whether wound healing is occurring. When developed, the PUSH tool explained 55% to 60% of the variance (p < .01) at Weeks 1 through 8. Because the PUSH tool involves only three parameters, it is easy to use and takes less than a minute to complete.

The PUSH tool was presented at a national conference, "Monitoring Pressure Ulcer Healing: An Alternative to Reverse Staging." Participants provided input regarding parameters, which included definitions, scoring, and directions for use during a structured forum. The recommendations included the following: the addition of tunneling, undermining, and volume; labeling size as length times width; describing exudate characteristics, as well as quantifying the amount; and scoring a healed ulcer as a 0 ⁽¹⁵⁾. The concept of PUSH was accepted with the understanding that an additional validation study with a larger number of patients would be conducted to address the recommended modifications. Data files of patients with pressure ulcers containing routine quantitative assessment of wound parameters were solicited for a validation study of the tool. This study reports the additional testing that has been conducted to validate the PUSH for tracking healing of stage II–IV pressure ulcers.

	Methods and Results

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Study 1
After the study was approved by the Committee on Human Research at the University of California-San Francisco, a convenience sample was recruited for this study that included subjects who were adults with a stage II–IV pressure ulcer, about which at least 4 weeks of data were available. Subjects were recruited from 10 sites that included clinics, nursing homes, research study sites, and home care settings. One ulcer per patient was selected.

A standardized data collection tool was created that included demographic variables and a weekly wound assessment. Study terms were operationally defined and provided in the instructions for the data collection tool. The staging system recommended by the Agency for Health Care Policy and Research's Pressure Ulcer Guideline Panel was utilized ⁽¹⁶⁾. Study forms were completed and submitted by each site. Data were scanned or manually entered into a computer program, and statistical analyses were performed.

Data were analyzed using SAS for Windows, version 6.12 (Statistical Analysis Institute, Inc, Cary, NC). Principal components analysis was used to answer the question of whether the PUSH items of surface area, exudate amount, and predominant tissue provided the most efficient measure of healing of pressure ulcers over time ⁽¹⁷⁾. Multiple regression was utilized to determine the sensitivity of the tool to measure healing over a 12-week period.

Study 1: Findings
The sample was composed of 273 subjects from 10 sites in eight states (Alabama, California, Connecticut, Iowa, Oregon, Missouri, Nebraska, and Pennsylvania) whose mean age was 74.6 years (SD, 15.0), about half of whom were women (50.7%). Eighty-one percent of the subjects were white, 17% were black, and 2% other. Complete data for 10 weeks or more were available for 103 subjects and were used for testing the PUSH tool. At baseline, stage III ulcers were recorded most frequently (47.4%), followed by stage II (34.9%) and stage IV (11.0%). A small portion (6.6%) of ulcers could not be staged. The mean ulcer area was 7.3 cm² (SD, 11.8), and the mean ulcer volume was 5.5 cm³ (SD, 14.8). The variables available for analysis were as follows: surface area, surface appearance, wound volume, exudate amount, exudate quality, tunneling, undermining, and wound edge characteristics.

Principal components analysis confirmed the PUSH variables of surface area, exudate amount, and surface appearance provided the best model of healing and accounted for 58% to 74% of the variation across the 10 weeks. Insertion of the other variables into the analysis did not significantly enhance the model.

To examine how well the model identified changes suggestive of healing over time, pairwise comparisons were done. Healing at baseline, measured by total PUSH score, was significantly different (p .05) from the total scores at each week (Weeks 1–10), as well as Week 1 versus Weeks 2 to 10, Week 2 versus Weeks 3 to 10, Week 3 versus Weeks 5 to 10, Week 4 versus Weeks 5 to 10, and Week 5 versus Weeks 7 to 10. Scores at Weeks 6 through 10 were not statistically different from each other, indicating the ulcers were healed or nearly healed. Multiple regression techniques indicated that the three variables explained 39% of the variance in healing in the first 6 weeks (p < .001).

Pilot Testing
After validation in Study 1, the PUSH tool was pilot tested in a long-term care facility. The results indicated that the existing five categories of wound size did not accurately reflect the larger pressure ulcers that are routinely encountered. In addition, the existing definition for scoring predominant tissue was not sensitive to the clinical concerns about the presence of any necrotic tissue. To address the size issue, the decision was made to expand the size variable into 10 categories and test it to see whether these divisions increased the tool's sensitivity. To address the issue of the sensitivity of tissue type, this parameter was modified so a higher score was given for the presence of any necrotic tissue. These new definitions are found in the Table A1 1. Thus, the original tool has been changed in three ways: (i) two instrument item titles have been refined (size was renamed "length x width," predominant tissue type was renamed "tissue type"); (ii) the length-times-width category has been expanded from five to 10 categories; (iii) the scoring has been simplified (the categories are no longer weighted, so the potential error in calculating a score has been reduced; the tissue-type item provides a mechanism to acknowledge the importance of any slough or necrotic tissue, not just when it covers more than 50% of the wound).

Study 2
The sample was composed of nursing home residents who were participating in the National Pressure Ulcer Long-term Care Study (NPULS) ⁽¹⁸⁾. This study was a secondary analysis of an existing data set and was utilized with no subject identifiers and so was exempt from review by the institutional review board. This study included residents who met the following criteria: aged 18 years or older, a resident of a long-term care facility for at least 14 days, and either at risk for or currently experiencing a pressure ulcer. One ulcer per subject was utilized. Only residents who had at least three complete ulcer assessments within 12 weeks were included in our study.

Dedicated personnel were trained in data extraction from the NPULS. Agreement among the personnel was greater than 95%. Data from NPULS were electronically downloaded to a central computer, and data for the PUSH analyses were selected. These data were analyzed using SAS for Windows, version 6.12 (Statistical Analysis Institute, Inc, Cary, NC). Principal components analysis was used to answer the question of whether the PUSH components as modified were validated in this sample. Multiple regression was utilized to determine the sensitivity of the model to measure healing over a 12-week period.

Study 2: Findings
The NPULS included 2490 residents, of whom 1274 had a pressure ulcer at initial assessment or developed a pressure ulcer during the subsequent 12-week study period. The mean age of the sample was 80 years (range, 18–102 years). There were 1746 (70%) women and 744 (30%) men. Residents came from 111 long-term care facilities. At baseline, stage II ulcers were reported most frequently (n = 1196), followed by stage I (n = 316), stage III (n = 219), and stage IV (n = 201). The remainder were not staged. Distribution of ulcer size is shown in Fig. 1. These ulcer sizes were used to increase the size categories in the PUSH tool from 5 to 10. The ulcers were located on the sacrum/coccyx (47%), heels (21%), buttocks (19%), and other sites (13%), including the iliac crests and trochanters. Two hundred sixty-nine subjects met the PUSH study inclusion criteria and were the sample for this testing. Utilizing one ulcer per subject (n = 269), 137 healed, and 132 did not heal.

View larger version (44K): [in this window] [in a new window]   Figure 1. Percentage of National Pressure Ulcer Long-term Care Study ulcers in each dectile by size (cm2).

Pairwise comparisons were performed to explore how well the model discriminated healing over time. Findings showed the total PUSH score at baseline was significantly different (p .05) from the total score at the following: all weeks, Week 1 versus all, Week 2 versus Weeks 3 to 12, Week 3 versus Weeks 5 to 12, Week 4 versus Weeks 5 to 12, and Week 6 versus Weeks 10 to 12. The other scores were not statistically different from each other, suggesting that the PUSH score in smaller ulcers or at terminal healing velocity is not as sensitive to change as it is in larger ulcers. Multiple regression analysis was used to determine the sensitivity of the tool to measure healing over the 12-week period. The total PUSH score was the dependent variable, and healed and not healed were the independent variables. Data showed that PUSH accounted for 31% of the variation (p < .001).

	Discussion

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A tool to measure healing must accurately reflect clinical reality. The tool must be consistent with outcome, that is, its score increases in wounds that deteriorate and decreases in wounds that heal. The tool must be sensitive to change, that is, the observer can see the progression of healing over time. The tool must demonstrate validity when tested on different populations. To be clinically useful, the tool must be simple to use. The PUSH tool has demonstrated these characteristics in the initial testing and has been revalidated in this study.

The PUSH model provides an accurate, simple, and clinically useful way to measure progress toward wound healing. Assessment of the ulcer characteristics of surface area, exudate amount, and surface appearance will provide the clinician with an indication of the healing of pressure ulcers over time. As scores decrease, healing is taking place.

The validated PUSH tool is shown in the Table A1 1. Surface area is measured as length times width. Surface area is expressed in dectiles, rather than as a continuous measure, as this reduces error due to slight differences in measurement. Exudate is estimated as the amount present, scored as none, light, moderate, or heavy. Tissue type refers to the types of tissue present in the ulcer bed. If there is any necrotic tissue present, it is scored as a 4, and if necrotic tissue is absent but any slough is present, it is scored as a 3. Granulation tissue receives a score of 2, and a superficial wound that is reepithelializing receives a 1. The closed wound receives a score of 0.

Other wound characteristics, such as exudate quality, initial ulcer stage, and wound edge status, have been suggested as markers for wound healing. Wound undermining or tunneling has been postulated to give additional information about progress toward healing. However, these variables were not present frequently enough that they added to the sensitivity of the tool. Further work may be needed to validate how often they occur and whether they contribute to the explained variance in healing.

The validation sample may have certain limits. Retrospective data were used in these analyses, and the findings are limited by what was documented. In many ways, these analyses represent real-world data and may more closely approximate clinical practice than that of highly controlled situations. Also, the tool is more sensitive to change early in healing but is accurate for monitoring healing throughout the repair trajectory. As wounds heal, there is a greater change in surface area initially than when the wound is almost completely closed ^(8)(19). The total score loses some of its discriminatory function as the ulcer closes. This expected loss of sensitivity is due to the difficulty of distinguishing small changes with integer numbers.

Further, preliminary analyses using dectiles and revised definitions show that these modifications did not detract from the ability of the original PUSH model ⁽¹⁴⁾ to explain healing. It is conceivable that the failure of PUSH version 3.0 to provide more explanatory power is due to the short period of time in which healing was monitored. The wounds in Study 2 were large (by design), and large wounds require a longer time to reach complete closure than do small wounds. More power may be obtained when large ulcers are studied if they are followed for a longer period.

The PUSH tool demonstrates the best combination of pressure ulcer characteristics that measure progress toward healing. This tool, as any other, is not intended to replace clinical judgment. The PUSH tool does allow a consistent, evidence-based methodology for communicating wound status toward healing among health care providers.

It is important to note that the PUSH Score is not designed as a comprehensive assessment paradigm for pressure ulcers and should not be used for that purpose. It is intended to provide a method for ongoing monitoring of healing. Other dimensions of assessment may be the basis for treatment decisions ⁽¹⁹⁾. Furthermore, the PUSH tool is not a research tool for measuring healing. It is a clinical tool to assist clinicians with routine evaluation of healing in day-to-day practice.

We recommend that PUSH be used to document healing of pressure ulcers as an alternative to reverse staging. Further refinement of the PUSH tool will likely result from prospective clinical studies. However, in its present form, it represents a practical alternative to reverse staging that will provide clinically valid data regarding pressure ulcer healing. Additional testing is needed to confirm these preliminary findings.

	Acknowledgments

 
This study was funded by the National Pressure Ulcer Advisory Panel. We thank the following individuals for providing subjects for this study: Janet Cuddigan and Joyce Black, Omaha, Nebraska; Catherine Eager and Deann Edgers, McMinnville, Oregon; Rita Frantz, Iowa City, Iowa; Gloria Lott, Hazelwood, Missouri; Cathy Milne and Lisa Corbett, Bristol, Connecticut; Patricia Pasceri, Norristown, Pennsylvania; Ginny Paulick, Bethel Park, Pennsylvania; Fran Schuda, Philadelphia, Pennsylvania; Jan Stanfield, Santa Clarita, California; David Thomas, Saint Louis, Missouri; Anne Voss and the Ross Products Division, Abbott Laboratories, Columbus, Ohio; and the National Pressure Ulcer Long Term Care Study Group.

Received January 25, 2001

Accepted February 14, 2001

	Appendix

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	References

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