The Development and Validation of a New Coeliac Disease Quality of Life Survey (CD-QOL)
The Development and Validation of a New Coeliac Disease Quality of Life Survey (CD-QOL)
Background Previous studies on coeliac disease (CD)-related quality of life (QOL) have been limited by their use of a 'generic' rather than coeliac disease-specific assessment instruments.
Aim To develop and psychometrically validate a new coeliac disease-specific instrument, the CD-QOL.
Methods Through a series of focus groups, we elicited items from patients that related to the specific nature of their disease and its impact on their basic needs. Through expert review, cognitive debriefing with patients and pilot testing, a scale was developed, refined and administered to 387 patients on a gluten-free diet from both community-based support groups and a tertiary care referral centre. Finally, a formal validation study was conducted to assess the psychometric properties of the CD-QOL.
Results The final CD-QOL has 20 items across four clinically relevant subscales (Limitations, Dysphoria, Health Concerns, and Inadequate Treatment). The CD-QOL has high internal consistency, reliability, and psychometric validation indicates both convergent and discriminate validity.
Conclusions The CD-QOL is a reliable and valid measure of coeliac disease related QOL. As a new disease-specific instrument, it is likely to be a useful tool for evaluating patients with this disorder.
Coeliac disease is a chronic disorder that can impact patients in many ways including their health-related quality of life (HRQOL). Several studies on HRQOL in coeliac disease (CD) have been conducted, but show variable results. In European studies, compared with the general population, patients with coeliac disease suffer a reduced HRQOL. Conversely, a Canadian survey suggested that the HRQOL of those with coeliac disease is similar to that of the general population. In the U.S., studies have not focused on HRQOL in coeliac disease, but rather on its clinical spectrum and the patient's perspective of its diagnosis and treatment. Nonetheless, because at the time of these studies there was no coeliac disease-specific HRQOL instruments, each of these studies used 'generic' assessment instruments. These generic functional status and symptom-based questionnaires may not adequately capture those attitudes, perceptions and needs that specifically relate to coeliac disease. This may result in findings that are less sensitive or responsive to treatment. Furthermore, because of the variable clinical presentation of individuals having this disease from asymptomatic to severely impaired, differences in the results may also reflect the clinical heterogeneity of the populations studied.
Accordingly, we developed a CD-specific QOL instrument, the CD-QOL. The methodology was similar to that used by our group to create other QOL measures. Furthermore, given the clinical heterogeneity of this population, we focused on developing and standardizing a measure that has clinical relevance, by targeting both those patients in the community who were members of local Coeliac disease support groups and patients seeking treatment for their symptoms at a major referral centre for coeliac disease. In this article, we report the results of a study to develop and assess the psychometric properties of the CD-specific QOL measure (CD-QOL) including conceptual and measurement model (subscale structure), reliability (internal consistency) and validity (content validity as well as convergent and discriminant construct validity).
Abstract and Introduction
Abstract
Background Previous studies on coeliac disease (CD)-related quality of life (QOL) have been limited by their use of a 'generic' rather than coeliac disease-specific assessment instruments.
Aim To develop and psychometrically validate a new coeliac disease-specific instrument, the CD-QOL.
Methods Through a series of focus groups, we elicited items from patients that related to the specific nature of their disease and its impact on their basic needs. Through expert review, cognitive debriefing with patients and pilot testing, a scale was developed, refined and administered to 387 patients on a gluten-free diet from both community-based support groups and a tertiary care referral centre. Finally, a formal validation study was conducted to assess the psychometric properties of the CD-QOL.
Results The final CD-QOL has 20 items across four clinically relevant subscales (Limitations, Dysphoria, Health Concerns, and Inadequate Treatment). The CD-QOL has high internal consistency, reliability, and psychometric validation indicates both convergent and discriminate validity.
Conclusions The CD-QOL is a reliable and valid measure of coeliac disease related QOL. As a new disease-specific instrument, it is likely to be a useful tool for evaluating patients with this disorder.
Introduction
Coeliac disease is a chronic disorder that can impact patients in many ways including their health-related quality of life (HRQOL). Several studies on HRQOL in coeliac disease (CD) have been conducted, but show variable results. In European studies, compared with the general population, patients with coeliac disease suffer a reduced HRQOL. Conversely, a Canadian survey suggested that the HRQOL of those with coeliac disease is similar to that of the general population. In the U.S., studies have not focused on HRQOL in coeliac disease, but rather on its clinical spectrum and the patient's perspective of its diagnosis and treatment. Nonetheless, because at the time of these studies there was no coeliac disease-specific HRQOL instruments, each of these studies used 'generic' assessment instruments. These generic functional status and symptom-based questionnaires may not adequately capture those attitudes, perceptions and needs that specifically relate to coeliac disease. This may result in findings that are less sensitive or responsive to treatment. Furthermore, because of the variable clinical presentation of individuals having this disease from asymptomatic to severely impaired, differences in the results may also reflect the clinical heterogeneity of the populations studied.
Accordingly, we developed a CD-specific QOL instrument, the CD-QOL. The methodology was similar to that used by our group to create other QOL measures. Furthermore, given the clinical heterogeneity of this population, we focused on developing and standardizing a measure that has clinical relevance, by targeting both those patients in the community who were members of local Coeliac disease support groups and patients seeking treatment for their symptoms at a major referral centre for coeliac disease. In this article, we report the results of a study to develop and assess the psychometric properties of the CD-specific QOL measure (CD-QOL) including conceptual and measurement model (subscale structure), reliability (internal consistency) and validity (content validity as well as convergent and discriminant construct validity).
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