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Pilot Evaluation of an Instrument to Measure Quality of Life in British Children With Inflammatory Bowel Disease

Ogden, Cassandra Anne*; Abbott, Janice*; Aggett, Peter*; Derkx, Bert H; Maity, Santanu; Thomas, Adrian G

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Journal of Pediatric Gastroenterology and Nutrition: January 2008 - Volume 46 - Issue 1 - p 117-120
doi: 10.1097/01.mpg.0000304467.45541.bb
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Abstract

In addition to physical symptoms associated with inflammatory bowel disease (IBD), there may be psychosocial effects (1–3). Children with IBD are more likely to have psychiatric morbidity (4) and impaired psychosocial functioning (5) than children with other chronic disorders. The World Health Organization defines health as a state of complete physical, mental, and social well-being (6). Health-related quality of life (HRQoL) research assesses how health, disease, or impairment affects physical, mental, cultural, environmental, and economic aspects of living (7). Outcome measures in IBD trials have traditionally relied on disease activity indices (8), but these measures fail to give a subjective view of the patients' experience. HRQoL instruments provide data that are meaningful to health professionals, patients, and their families (9–11). They complement information from disease activity indices and can evaluate how treatments affect patients' lives. HRQoL instruments for adults with IBD include the IBD Questionnaire (8) and the Rating Form of IBD Patients' Concerns (12), but these are unsuitable for and have not been validated in children.

The first HRQoL instrument for children with IBD (the IMPACT instrument) was developed in Canada by interviewing 82 children and adolescent subjects with IBD (13). An item reduction list was constructed from 94 issues or concerns identified by the children, in addition to 2 additional issues from the IBD Questionnaire. The 96 issues were ranked in order of importance by a further 117 Canadian children with IBD. The top 50 issues formed the 33 item IMPACT questionnaire consisting of 6 domains: bowel symptoms, body image, functional/social impairment, emotional impairment, test/treatments, and systemic impairment. The IMPACT instrument was subsequently validated in Canada (14).

A cross-cultural comparison showed a significant correlation between the concerns of British and Canadian children with IBD (15), but British and Dutch children found the original Canadian IMPACT instrument too complicated and/or upsetting. The IMPACT questionnaire was translated and adapted for Dutch children with IBD. A time scale was inserted, the questions were simplified, and the modified 35-item Dutch version of the IMPACT instrument was validated (16). Seventy-two children with IBD—41 from Canada, 11 from Amsterdam, the Netherlands; and 20 from Manchester, UK—completed the original IMPACT instrument and the modified version. Forty-two children stated a preference for one of the instruments, with 30 preferring the modified version of the IMPACT instrument (17). A Dutch study on the use of response scales (18) showed that children preferred a Likert scale because it was easier to complete than a visual analog scale (VAS). It was suggested that the IMPACT questionnaire may benefit from a Likert scale rather than a VAS.

The present study aimed to identify changes needed to adapt the IMPACT instrument for use in British children with IBD and to see whether children preferred the Likert scale or the VAS.

MATERIALS AND METHODS

The simplified Dutch version of the IMPACT instrument was translated back into English by 2 independent translators and any differences were resolved by consensus. The final resulting version (IMPACT-UK) was checked by the original Canadian developers of IMPACT, the Dutch researchers, and the present investigators to ensure that the original concepts were maintained. These researchers, which included 3 quality of life methodologists and an IBD research nurse, formed a multidisciplinary committee (including several members fluent in Dutch and English) who agreed on the methodology for validation and translation (as proposed by Guillemin et al (19)) of the IMPACT questionnaire. Although the Dutch and UK versions of the IMPACT instrument retained the original concepts of the Canadian IMPACT questionnaire, it was believed that because of the modifications described, further validation would be required in both countries.

Two versions of the IMPACT-UK instrument incorporating different response scales (VAS and Likert scale) were used to determine which scale British children preferred. The VAS consisted of a 10-cm line with 2 extreme response options at each end whereas the Likert scale had 5 discrete points. Twenty children with IBD completed both versions of the IMPACT-UK questionnaire immediately after one another in random order. They were asked which response scale they preferred and why, whether they had any difficulty understanding the questions or response options, whether they thought the questions were relevant, and how they could be improved. Four respondents had cognitive interviews and were asked to “think aloud” about their understanding of the questions and the reasons for their answers. Any words or phrases that the children had difficulty in understanding would be modified before formal validation of the IMPACT-UK instrument. To compare the Likert scale and VAS versions of the IMPACT-UK instrument, the overall mean scores and domain scores of each version were calculated and transformed. The domains had previously been identified by Loonen et al (16). The Likert scale was coded from 0 to 4 on each item (total IMPACT score, 0–140). The scores were translated to a scale of 0 to 100 by totalling all item scores for the domain, dividing by the total possible score for that domain, and then multiplying by 100. The VAS was scored by measuring the distance in millimeters between the leftmost point of the line to the respondent's mark. All item scores for the domain were added together and then divided by the total number of items in the domain. The χ2 test was used to see which scale the children preferred.

The study was approved by the Salford and Trafford Research and Ethics Committee. Children were recruited from the gastroenterology outpatient clinic at Booth Hall Children's Hospital, Manchester, UK.

RESULTS

Characteristics of the children who participated are shown in Table 1. All children believed all the questions were relevant. Five children (ages 8–12 years; 3 with Crohn disease, 1 with ulcerative colitis, and 1 with indeterminate colitis) had difficulty understanding certain words. They did not know what “restrictions” meant, they knew what inflammatory bowel disease was but not the abbreviation “IBD,” and they understood the word “diarrhea” when spoken aloud but could not read it as “diarrhoea.” “Moderate” was a response option in the Likert scale and some children only guessed that it meant “in the middle” because of its positioning on the scale. Participants distinguished between the responses in the Likert scale and related their answers to the response options proficiently. Eight respondents had difficulty with question 35, “Has your school been on a break during the past 2 weeks? If not, during those past 2 weeks how often could you go to school?” They thought the question was asking if their school had lunch and play breaks. By the end of the study, no new problems were being reported by the subjects, suggesting that the sample size was adequate.

TABLE 1
TABLE 1:
Characteristics of study sample

Fifteen participants preferred the Likert scale because they believed it was quicker and easier to complete, whereas those who preferred the VAS believed it was more accurate. The mean overall scores for the 2 scales were similar, but there were significant differences in the body image and IBD symptom domains (Table 2).

TABLE 2
TABLE 2:
Likert and VAS scores for all respondents

DISCUSSION

The cross-cultural comparison by Richardson et al (15) showed that British children with IBD had similar concerns as Canadian children with IBD. The aim of this study was to identify the changes needed to adapt the IMPACT instrument for use in children with IBD in the UK and to determine the preferred response scale.

Certain words or phrases caused difficulty for some of the children. We propose the following changes to make the questionnaire more child-friendly: “restrictions” to be changed to “limits,” “moderate” to be replaced with “quite a bit,” “diarrhoea” to be followed by the explanation “loose or frequent bowel movements,” “IBD” to be replaced by “inflammatory bowel disease,” and the question about school attendance to be rephrased, “How often are you able to go to school?”

As in the previous Dutch study (18), most children preferred the Likert scale and believed it was easier to complete. It is therefore proposed to use this in the IMPACT-UK questionnaire to facilitate self-completion. Calculation of scores from a VAS is time-consuming and laborious, whereas the Likert scale options have a preassigned values, facilitating calculation of the score. The mean overall scores of both versions of the IMPACT instrument were similar, but there were significant differences in the body image and IBD symptom domains, thus confirming the need for further psychometric validation of the IMPACT-UK instrument.

The present study shows that the IMPACT instrument needs modifications in language, phrasing, and response scale for British children to fully understand the instrument and complete it by themselves. With the proposed modifications, it should be suitable for British children with IBD but further psychometric evaluation is needed to ensure that the instrument is reliable and valid. The IMPACT-UK questionnaire could then be used to assess patients in the clinical setting and as an outcome measure in clinical trials. Its development for use in the UK will also help contribute to our understanding about the effects of IBD on affected children.

Acknowledgment

The authors acknowledge the considerable help of Dr Hester van Der Zaag Loonen in the planning of this study.

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Keywords:

Crohn disease; IMPACT instrument; Inflammatory bowel disease; Health-related quality of life

© 2008 Lippincott Williams & Wilkins, Inc.