DEVELOPMENT OF A NEW FAECAL INCONTINENCE SCALE

The Wexner Continence Grading Scale4 has become a widely used for the assessment of severity of faecal incontinence. It is simple to use and easily understood by patients. We felt that there were three areas in which this scale could be improved. Firstly, the scale does not take account of faecal urgency, which can be present without overt faecal incontinence. Secondly, the need to wear a pad is given equal weighting to the occurrence of incontinence. However the use of a pad may not be a measure of the severity of faecal incontinence, but rather reflect the patient’s degree of fastidiousness. The use of a pad also often relates to the presence of coexistent urinary leakage. Finally, in the comparison of degree of incontinence preoperatively and postoperatively, the introduction of antidiarrhoeal drugs should be taken into account. These are often given as a part of the treatment package and a failure to recognise this could give a false impression of the surgical success rate. In developing a new scale, we felt that the Wexner scale formed an excellent basis, but with these modifications.

Our new scale (see table 4) has introduced an assessment of the ability to defer defecation and an additional score for the use of antidiarrhoeals, and reduced the emphasis on the need to wear a pad.

STUDY 1—CORRELATION OF SCORING SYSTEMS WITH CLINICAL ASSESSMENT

Twenty three consecutive patients (21 females, median age 57 years, range 30–78 years) with faecal incontinence, referred for anorectal physiological testing, were prospectively evaluated. It was calculated that a sample size of 23 would be sufficient to detect a correlation of 0.55 or better at the 5% significance level with 80% power. Eight had passive incontinence, seven had urge incontinence, and eight had both passive and urge incontinence. A further healthy female volunteer, aged 57 years, without faecal incontinence, was added to the group as a negative control. This was mainly for the purpose of ensuring that all questions were unambiguous.

We chose the most recently developed and commonly used scores for evaluation: the Pescatori3 (table 1), Wexner4(table 2), American Medical Systems (AMS)5 (table 3), and our new scale (table 4).

Two investigators (CJV and EC) independently took a detailed history from each patient and had access to examination findings, anorectal physiological tests, and the endoanal ultrasound. Each then gave the patient a “clinical score”, on the scale of 0 to 20, designed to reflect the severity of faecal incontinence based on the clinical information without use of a formal scoring systems. A third investigator (JAC) did not take a history or have access to clinical information but assisted the patients with the written incontinence scoring systems. All three investigators were blinded to each other’s results.

As a separate measure, each patient was sent home with a 28 day scored diary (fig 1). Items were each allocated a numerical value based on our perceived estimate of the severity of a particular symptom, ranging from 0.5 to 2, with a possible maximum score of 10 each day, and a possible maximum for the 28 days of 280.

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Figure 1

Diary card. The patients were sent home with 28 of these diary cards and requested to fill out one each night for four weeks. Each positive answer resulted in a numerical score as listed. Maximum score per day = 10 = worst incontinence.

STUDY 2—TEST-RETEST RELIABILTY OF SCORING SYSTEMS

Retesting using each of the four scoring systems was performed on a randomly selected subset of 13 of the 24 patients at a median of 14 days (range 8–20 days) after the first test. Retesting 13 patients allowed estimation of correlation of 0.7% or better at the 5% significance level with 80% power.

STUDY 3—PREOPERATIVE AND POSTOPERATIVE ASSESSMENTS (SENSITIVITY OF SCALES TO CHANGE)

A further 10 female patients (median age 57 years, range 31–64), were prospectively evaluated using the four scoring systems before and six weeks after surgery for faecal incontinence. The improvement in incontinence scores was then correlated with the investigators’ assessment of improvement. Five patients underwent an overlapping anterior sphincter repair7 for obstetric damage and five underwent implantation of an artificial bowel sphincter.8

STATISTICAL METHODS

To compare the clinical assessment with the four incontinence scales and the diary card, all scores were converted to percentages. The data were found to be normally distributed using the Shapiro Francia W′ test. Statistical analysis by pairedt test compared the mean of the clinical impression scores of investigators 1 (CJV) and 2 (EM). Analysis of variance (ANOVA) was used to determine interobserver reliability using the variance between observers, between patients, and error. The mean of the clinical impression scores for the two observers was then correlated with each of the incontinence scoring systems using the Pearson correlation. The test-retest reliability was calculated as the proportion of the total variability (patients + occasions + error) due to variation between patients. A value of p<0.05 was considered significant.

STUDY 1—CORRELATION OF SCORING SYSTEMS WITH CLINICAL ASSESSMENT

Table 5 details the clinical and grading scale scores. Eighteen of 23 patients (78%) completed and returned the 28 day diary card. The mean (SD) diary score was 91 (59), range 0 to 205. There was no significant difference between the mean clinical impression scores of investigators 1 and 2 (difference in means 4.2, 95% confidence interval −0.8 to 9.1, p=0.09, paired ttest). There was no significant bias between the two observers. The interobserver reliability was 0.88 (ANOVA). The mean of the two clinical impression scores was correlated with each of the incontinence grading scales. Table 6 summarises correlation coefficients. The control scored zero on clinical assessment and on all of the scoring systems evaluated. There were significant correlations between the mean clinical impressions and all the incontinence grading systems. The highest correlation was with our newly devised scale and the Wexner scale, and the lowest with the AMS score.

STUDY 2—TEST-RETEST RELIABILITY OF SCORING SYSTEMS

Table 7 summarises the estimated variance components and test-retest reliability of the four scales. Values of zero equated to occasions where there was a negative value for variance components. The newly devised scale had the highest test-retest reliability.

STUDY 3—PREOPERATIVE AND POSTOPERATIVE ASSESSMENTS (SENSITIVITY OF SCALES TO CHANGE)

There were significant changes for all scores except for the AMS score, but the largest and the most significant change was for the newly devised scale (table 8). There were significant correlations between all incontinence grading systems and the investigators’ assessment of improvement, the highest correlation being for the newly devised scale and the lowest for the AMS scale (table9).