Wound bed score and its correlation with healing of chronic wounds

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Dermatologic Therapy, Vol. 19, 2006, 383390

Printed in the United States All rights reservedCopyright Blackwell Publishing, Inc., 2006

DERMATOLOGIC THERAPY

ISSN 1396-0296

BlackwellPublishing Inc

Wound bed score and itscorrelation with healing of chronic

woundsVINCENT FALANGA

*

, L

ILIANA

J. S

AAP

*, & A

LEXANDER

O

ZONOFF

*

Department of Dermatology and Skin Surgery, Roger Williams MedicalCenter, Providence, Rhode Island,

Departments of Dermatology andBiochemistry and

Department of Biostatistics, Boston University, Boston,Massachusetts

ABSTRACT:

Adequate wound bed preparation is essential for healing of leg ulcers, and consists ofcontrolling exudate and edema, decreasing the bacterial burden, promoting healthy granulationtissue, and removing necrotic tissue. Currently, there is no classification system for wound bed prep-aration that has predictive value. Based on past work and the authors experience, we have nowdeveloped and tested a new classification system that scores the following parameters: healing edges(wound edge effect), presence of eschar, greatest wound depth/granulation tissue, amount of exudateamount, edema, peri-wound dermatitis, peri-wound callus and or fibrosis, and a pink/red woundbed. Each parameter receives a score from 0 (worst score) to 2 (best score), and all the parameterscores are added for a total score. Each wound can have a maximum score of 16 (the best scorepossible), to a minimum score of 0 (the worst score possible). We used this wound bed score (WBS)system in a study of 177 patients with venous ulcers who had been prospectively treated with andrandomized to either conventional therapy (compression alone) or a living bilayered skin construct(BSC). We evaluated serial photographs at baseline to determine whether the results would be predic-

tive of complete wound closure and could validate the WBS. We found that wounds that ultimatelyachieved full closure had a statistically significant higher WBS than those that did not heal(

p =

0.0012). This was also true when separating wounds by treatment modality: standard therapy(

p =

0.044) and treatment with a BSC (

p =

0.011). When dividing the WBS in the following quartilegroups: scores 410, 1012, 1213, and 1316, the percentage of healed wounds correlated with the

WBS (

p =

0.0008). For all wounds, a one unit increase in total WBS resulted on average in a 22.8%increase in odds of healing (OR = 1.228). This WBS seems to have validity in predicting complete

wound closure in wounds treated with either standard therapy or advanced modalities, such as BSC.If confirmed and widely adopted in this and other types of wounds, it could be a useful tool in boththe clinical and research setting.

KEYWORDS:

bioengineered skin, prognosis, skin equivalents, wound, wound bed preparation, woundhealing

Introduction

It is estimated that in the United States, between400,000 and 500,000 patients are affected byvenous leg ulcers. However, the true prevalence isprobably higher and is likely to become largerwith the ever-increasing elderly population.Venous leg ulcers account for 8090% of allchronic wounds of the lower extremity (1). Adequate

Address correspondence and reprint requests to: Vincent

Falanga, MD, FACP, Professor of Dermatology and

Biochemistry, Department of Dermatology, Roger Williams

Medical Center, 50 Maude Street, Providence, RI 02908, or

email: [email protected].

Dr Saap is presently with Affiliated Dermatology Cosmetic

Surgery Center, Dublin, OH.


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wound bed preparation is essential for healingof chronic wounds, and consists of controllingexudate and edema, decreasing the bacterialburden, promoting healthy granulation tissue,and removing necrotic tissue (13). Currently, thereis no classification system for wound bed prepa-

ration that can predict ultimate wound closure(3). In 2000, we pioneered the concept of woundbed preparation and proposed a classificationsystem for it (35). This scoring system consistedof a wound bed appearance score and an exudatescore that were added together to give eachwound a total score (Table 1). For example, a scoreof B2 would signify a granulation tissue between50% and 100% and a moderate amount of exu-date. The appearance score took into account theamount of granulation tissue, fibrinous material,and eschar. That classification system remainsvery useful for describing the wound bed. How-

ever, we wanted to know whether it would alsohave predictive value for ultimate wound closure.Therefore, in further work (6) we applied thatclassification system to venous ulcers treated eitherwith standard therapy or a bilayered bioengineeredskin construct (BSC). The data showed thatminimal exudate and lack of an eschar closelycorrelated with increased healing. However, wefound that the extent of granulation tissue andfibrinous material were not as helpful and did notadd substantially to the predictive value of thatscoring system.

We have now devised a wound bed score (WBS)that reflects our previous work and clinical experi-ence. The WBS includes the following parametersthat are not limited to the absolute wound bed alone

and also includes the surrounding diseased skin:(a) healing edges (wound edge effect); (b) blackeschar; (c) greatest wound depth/granulation tis-sue; (d) amount of exudate, edema, peri-wounddermatitis, peri-wound callus and or fibrosis; and(e) a pink wound bed (Table 2

)

. Each individual

parameter receives a score from 0 (worst score) to2 (best score), and all the parameter scores areadded for a total score. A wound can have amaximum WBS of 16 (the best possible score), toa minimum WBS of 0 (the worst possible score).Some representative examples are shown inFIGS 1 and 2. In this report, we applied this scor-ing system to a group of patients with venousulcers randomized to treatment over a 24-weekperiod with either conventional therapy (com-pression bandages alone) or also receiving a livingBSC. The results of this study are very promising,showing that the WBS is valid in assessing wound

bed preparation and predicting whether ultimatewound closure occurs.

Patients and methods

Patients

The details of the clinical trial used for the presentanalysis of venous ulcers have been previouslypublished (4). We made use of data generatedfrom the pivotal controlled, randomized trial

that led to Food and Drug Administration approvalof a bilayered BSC (also known as Apligraf, Organo-genesis, Inc., Canton, MA) in the treatment venousulcers (4). Photographs from a total of 177 venous

Table 1. Initial Wound Bed Preparation Score Developed in 2000a

Wound bedappearance score

Wound bed characteristics

Granulation tissue (%) Fibrinous tissue Eschar

A 100 B 50100 +

C < 50 + D Any amount + +

Wound exudatescore

Extent ofcontrol

Exudateamount

Dressingrequirement

1 Fully None/minimal No absorptive dressings requiredIf feasible, dressings could stay on for up to a week

2 Partially Moderate amount Dressing changes required every 23 days3 Uncontrolled Very exudative wound Absorptive dressing changes required at least daily

aAdapted from Falanga V. Classifications for wound bed preparation and stimulation of chronic wounds. Wound Rep Reg 2000;

8 : 347352. Copyright V. Falanga, 2000.


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ulcer patients at day 1 were evaluated and scored.Of these patients, 83 were treated with standardaccepted conventional therapy (compression alone)and 94 were treated with BSC. The inclusion criteriafor these patients were the following: ages 1885;venous insufficiency, history of nonhealing venousulcers of longer than 1 months duration; andvenous ulcers extending through the epidermisinto dermal tissue, but without exposed bone ortendon. The main exclusion criteria were: venousulcer size area of less than 1 cm

2

or more than10

20 cm, arterial insufficiency (ABI < 0.65), andmedical conditions known to impair healing (4).Informed consent was obtained of all patientsin accordance to each study centers human

research committee, and the study protocolsconformed to the ethical guidelines of the 1975Declaration of Helsinki.

Treatment and evaluation

Evaluation of the photographs was performed bya blinded observer who had had no involvementin the trial. The photographs to be evaluated were

Table 2. New Wound Bed Score ( WBS) and Its Individual Featuresa

Wound bed scorecharacteristics 0 1 2

Healing edges None 2575% > 75%Black eschar > 25% of wound 025% None

surface area

Greatest wound Severely depressed or Moderate Flushed orDepth/granulation raised when compared to almost evenTissue peri-wound skinExudate amount Severe Moderate None/mildEdema Severe Moderate None/mildPeri-wound Severe Moderate None orDermatitis minimalPeri-wound Severe Moderate None orCallus/fibrosis minimalPink wound bed None 5075% > 75%

aThe total WBS adds each individual score for each characteristic to give a total score. The maximum possible score (best score) is

16. The minimum possible score (worst score) is 0.

FIG. 1. Steep wound edges. This is an example of a venousulcer with pink and adequate granulation tissue but with

steep edges. This feature is strongly associated with impaired

healing. No eschar is present.

FIG. 2. Healing wound edges (edge effect). This is a venousulcer that is going to heal. The thick oval shows a portion of

the wound demonstrating the edge effect whereas the thin

oval shows a part of the wound with no edge effect. This

particular wound has no black eschar. The thick black arrow

points to the wound bed that is raised in comparison to the

peri-wound skin, whereas the thin black arrow points to the

wound bed that is flush with the peri-wound skin. This wound

also shows an excellent example of peri-wound fibrosis as

demonstrated by the blue arrow.


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those taken at day 1 of the study, prior to assign-ment to either of the two treatment arms. Thecontrol venous ulcer patients were treated withstandard therapy consisting of a nonadherentprimary dressing (Tegapore, registered trademark3M Health Care, St Paul, MN), a secondary gauze

pressure bolster, a zinc paste bandage (Unnaboot), and a self-adherent elastic wrap (Coban,3M Health Care); or with the BSC applied directlyto the wound, followed by the nonadherentprimary dressing, cotton gauze dressing foldedas a bolster, and the same elastic wrap. Patientsreceived up to five applications of BSC within thefirst 21 days of the study. Re-application wasperformed if less than 50% of the wound had re-epithelialized (4). The original trial had a total of146 patients treated with the BSC and 129 in thecontrol group. However, evaluable photographsfor the purpose of the present study were only

available from 83 control patients and 94 BSC-treated patients. This was either the result ofpictures not being taken at day 1 or patients leavingthe study prematurely so that healing or lack ofhealing could not be assessed. Patients werefollowed for a total of 12 months, and healing wasdetermined as 100% epithelialization with nowound drainage by week 24.

Statistical analysis

The WBS was applied to each patient photograph,

as explained earlier. Healing percentages for eachscore were determined by using the case reportforms provided for each patient. The independentsamples t

-test was used to compare mean WBSbetween healed and not healed wounds in allpatients, including control and BSC-treatedpatients. This test was also used to compare meanWBS between wounds that healed and those thatdid not heal based on initial wound duration ofeither less than 1 year to greater than 1 year priorto enrollment into the protocol. The Cochran-Armitage trend test was used to evaluate theassociation and trend between the WBS and com-plete wound closure. Logistic regression was usedto model total WBS as a predictor for healing status(as a binary outcome) and to model total WBSprior to treatment as a predictor for the durationof wound. Finally, probability of healing wasmodeled with a stepwise logistic regression model,which includes each individual characteristicone at a time, with an entry/removal thresholdof p

= 0.10. This procedure allowed the presentauthors to assess each individual characteristicfor its predictive power in the model.

Results

As stated earlier, photographs had not been sub-mitted at day 1 for all study participants. There-fore, we were not able to analyze all the patientsinitially enrolled in the study trial. These drop-

outs were not included in the data set for analysisas there was no complete data for these subjectsto analyze. This also means that there was no wayto assess potential differential drop-out rates forany of the subgroups used in the analyses. Forthese reasons, we decided to omit the survivalanalysis, although we examined association betweentime-to-heal and bed score with other methods.Therefore, photographs were evaluated for 177patients at day 1 before any treatment was insti-tuted. Of these 177 patients, 94 were treated withBSC and 83 were treated with standard therapy(control) as described in the methods section.

Using the independent samples t

-test, wefound that the WBS at baseline was higher in thesubjects who healed (WBS = 11.83) compared tothose who did not heal by the 24-week mark(WBS = 10.62; p

= 0.0012). We also saw similarresults after separating the patients according totreatment. Mean WBS score for patients treatedwith BSC was significantly higher in patients whohealed (11.87) versus those patients who did notheal (10.59) (

p =

0.0113). In patients treated withstandard therapy, mean WBS score was also sig-nificantly higher in patients who healed (11.79)

versus those who did not heal (10.66) (

p =

0.0439).We then took the total WBS for all wounds (controland treatment groups) and divided them into thefollowing four groups using roughly equiprobablecut-off values or quartiles: 410, 1012, 1213, and1316. We found a statistically significant trendshowing higher healing percentages for the WBS inthe higher quartiles (

p =

0.0008 Cochran-Armitagetrend test) (FIG. 3).

Using logistic regression to model total WBS(for both control and BSC-treated wounds) as apredictor for healing status, we obtained the oddsratio of 1.228 (

p =

0.002). This can be interpreted asmeaning that one unit increase in total WBSresulted on average in a 22.8% increase in theodds of healing. For example, increasing the totalWBS from 10 to 13 leads to a 1.228 or 1.85-foldincrease in the odds of healing. The odds ratio forwounds treated with BSC alone was 1.253(

p =

0.015) and for standard therapy alone was 1.202(

p =

0.010). Once again, this means that a one unitincrease in WBS leads to a 25.3% and a 20.2%increase in odds of healing for wounds treatedwith BSC and standard therapy, respectively.


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For all patients, regardless of treatment, weevaluated the WBS and correlated it to time toheal. It was found that a higher WBS, although notstatistically significant, did show a trend towardshorter healing time (

r =

0.146, p

= 0.15). We thentook all the patients that did heal and tested theassociation between time to heal and total WBSusing the Wilcoxon rank-sum test. Time to healwas categorized into low (= 8 weeks) and high(> 8 weeks) time to heal groups. Once again, we

found a strong correlation trend between higherWBS and lower time to heal (

p =

0.064).We further evaluated WBS for all wounds and

correlated it to wound duration before treatment.Wounds with a duration of less than 1 year hada higher mean WBS (11.81) than wounds thathad been present for more than a year (10.84)(

p =

0.0086). We estimated an odds ratio of 1.1179(

p =

0.010) when logistic regression was used tomodel total WBS as a predictor for wound healingfor those wounds with a duration of less than 1year. Once again, this can be interpreted as fol-lows: a one-unit increase in total WBS prior totreatment will result in an increase of 17.9% in oddsof healing.

When separating for treatment, wounds treatedwith BSC also showed a statistically significanthigher mean WBS for wounds with less than 1year in duration (12.05) than wounds present formore than a year (10.78) (

p =

0.0128). The odds ratiowas 1.260 (

p =

0.016) for wounds with a healingduration of less than 1 year. For wounds treatedwith standard therapy, there was a trend, althoughnot statistically significant, showing higher WBS

(11.62) in wounds with less than 1 year in durationthan wounds with more than 1 year duration(WBS = 10.92; p

= 0.2156).Noting that wound duration before treatment

is an important factor in predicting ultimatewound closure, we decided to modify the WBS

slightly by adding wound duration (a historicalparameter) as an additional parameter (Table 3).This was done to determine whether this wouldalso have an effect on total WBS and ultimatehealing. Using this modified WBS, we found thatregardless of treatment those wounds that healedstill had a higher mean WBS (13.14) than thosethat did not heal (WBS = 11.15; p

= 0.0001). Logisticregression to model probability of healing estimatedan odds ratio of 1.312 (

p 75%Black eschar > 25% of wound 025% None

surface area

Greatest wound Severely depressed or Moderate Flushed orDepth/granulation raised when compared to almost evenTissue peri-wound skinExudate amount Severe Moderate None/mildEdema Severe Moderate None/mildPeri-wound Severe Moderate None orDermatitis minimalPeri-wound Severe Moderate None orCallus/fibrosis minimalPink wound bed None 5075% > 75%

Wound duration Greater or equal to Less thanPrior to treatment 1 year 1 year

The total WBS adds each individual score for each characteristic to give a total score.

The maximum possible score (best score) is 18.The minimum possible score (worst score) is 0.

Table 4. Characteristics of components in the total WBS with the most predictive value for ultimatewound healing, as assessed by a stepwise logistic regression model

Effect OR High odds group pvalue 95% CI

Edges (2 versus 0) 1.783 2 0.055 (0.63, 5.08)Edges (1 versus 0) 0.744 1 0.133 (0.26, 2.17)P.callus/fibrosis (2 versus 0) 9.335 2 0.006 (2.03, 42.83)P.callus/fibrosis (1 versus 0) 1.998 1 0.334 (0.79, 5.05)Duration in years (= 1 versus > 1) 4.579 = 1 < 0.0001 (2.24, 9.35)

= 0.10 used as stopping threshold for stepwise selection.


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outcome. We have learned about the importanceof these parameters mostly from clinical experi-ence, but there are few clinical trials that haveevaluated the importance of each characteristic(79). Importantly, it remains unclear what spe-cific endpoints in the appearance of the wound

would improve healing or suggest alternativetreatments with advanced therapeutic modalities.About 5 years ago, in formally outlining the

concept of wound bed preparation, we proposeda classification system to evaluate wound bedpreparation (2,10). The published classification isindeed helpful in describing the wound, as itcaptures the state of the epidermis, granulationtissue, and the degree of exudate. In formulatingthat classification, we relied on the traditional viewfrom purely clinical experience that the amountof granulation tissue may be critical. However,either this parameter is not as important as initially

thought, or it might be that other attributes areequally if not more critical to ultimate wound clo-sure. Thus, initial analysis using that classificationsystem showed that some of the parameters,whereas clinically useful in documenting thecourse of the wound, did not have the prognosticsignificance we had hoped for (6) (FIG. 4). Theanalysis showed that exudate control and minimaleschar led to improved healing. However, some-what surprisingly, minimal fibrinous material andmaximal granulation tissue did not necessarilylead to improved healing.

Therefore, we felt that we needed to go back tothe drawing board and use our clinical experienceto identify parameters that seemed to correlate

with healing. The parameters we determined tobe promising were the following: healing edges(wound edge effect), black eschar, greatest wounddepth/granulation tissue, exudate amount, edema,peri-wound dermatitis, peri-wound callus and orfibrosis, and a pale or pink wound bed. It should

be noted that a very red granulation tissue mayoften indicate bacterial infection. The exudateamount and black eschar had been shown in ourprevious analysis to be significant. We have notedthat wounds with an established wound edge effect,that is, a wound edge that has faint epithelial cellsgently sloping towards the wound (no steep edge),have a higher chance of healing. Interestingly,wounds that have fibrinous material may still healas long as the wound is flush with the edges andnot depressed. On the other spectrum, impairedhealing is seen with wounds that have abundantbut raised granulation tissue.

Wound bed exudate is important, but so isperi-wound dermatitis. Peri-wound callus has beenshown to be important in diabetic foot ulcers, andnot in venous ulcers and without the presence ofpressure forces. This is the reason we combinedperi-wound callus with peri-wound fibrosis. Inour clinical experience, wounds with peri-woundfibrosis also have difficulty healing. Finally, awound bed that has a pink, but not red color maybe more desirable. An intensely red granulationtissue may actually reflect increased bacterialcolonization and inflammation. Taken together,

these considerations based on previous analysesand clinical experience led us to propose a newWBS that could be tested for wound bed prepara-tion and prognostic value.

In this report, we found that the new proposedWBS can predict healing. Regardless of whetherthey were treated with compression alone or witha living BSC, wounds with a higher total WBS hada higher probability of complete wound closurehealing. In support of other work and clinicalexperience, wounds with duration of less than 1year also had a higher WBS. Although all the com-bined parameters of the WBS were important inimproving the probability of healing, the follow-ing three parameters had the strongest predictivepower: wound edge effect, peri-wound callus/fibrosis and wound duration prior to initiation oftreatment.

In conclusion, we have devised a WBS that,when used at baseline, appears promising inpredicting ultimate wound bed closure. This WBSmay be useful both in clinical studies and in clini-cal practice to optimize treatment modalities anddesign and test new treatments. Further studies

FIG. 4. Percentage of healed venous ulcers and correlationwith initial the scoring system published in 2000 (2).


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are going to be required to use the WBS prospec-tively in cohorts of patients with different types ofchronic wounds. Ideally, one would like the WBSto be applicable to wound bed preparation ingeneral, regardless of the etiology of the chronicwound.

Acknowledgments

This study was funded by NIH grants AR42936,AR46557, DK067836 (VF), and the Wound Bio-technology Foundation.

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Wound bed score and its correlation with healing of chronic wounds