Validity and reliability of an Italian version of the revised Leeds disability questionnaire for patients with ankylosing spondylitis

E. Lubrano, P. Sarzi Puttini1, W. J. Parsons3, S. D'Angelo, M. A. Cimmino2, F. Serino and N. Pappone

Fondazione Maugeri, IRCCS, Istituto Telese Terme, Rheumatology and Rehabilitation Research Unit, Telese Terme (BN), 1 University Hospital L. Sacco, Rheumatology and Internal Medicine, Milano, 2 University of Genova, Academic Rheumatology Unit, Genova, Liguria, Italy and 3 The Leeds Teaching Hospitals NHS Trust, Research and Development, Leeds, UK.

Correspondence to: E. Lubrano, Fondazione Maugeri, IRCCS, Istituto Telese Terme, Rheumatology and Rehabilitation Research Unit, Telese Terme (BN), Campania, Italy. E-mail: enniolubrano{at}hotmail.com; elubrano{at}fsm.it


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Objective. The purpose of the present study was to produce an Italian version of the Revised Leeds Disability Questionnaire (LDQ) in a group of patients with ankylosing spondylitis, and to examine the psychometric properties of this version, evaluating its internal consistency, external validity and reliability.

Methods. The LDQ was administered to 60 Caucasian patients affected by ankylosing spondylitis (50 males, 10 females, mean age 46.1 ± 14.2 yr, range 22–74, median disease duration 4.5 yr, range 1–24) together with the Italian version of the Stanford Health Assessment Questionnaire (HAQ), and anthropometric measurements. Thirty patients completed the questionnaire after a 10-day interval. Internal consistency was evaluated with Cronbach's {alpha} coefficient of reliability. Construct validity of the LDQ was evaluated using the correlation between the HAQ and anthropometric measurements. Test–retest reliability was assessed with the intraclass correlation coefficient.

Results. All patients completed the validation study. The questionnaire was internally consistent ({alpha}=0.90). A significant correlation was recorded between the LDQ and the HAQ score ({rho}=0.841, P<0.01) and the anthropometric measurements. Test–retest reliability showed a good correlation coefficient (intraclass correlation=0.97).

Conclusion. The Italian LDQ is a valid and reliable instrument for detecting and measuring functional disability in patients with ankylosing spondylitis. Our results confirm the utility of this questionnaire as a valid and feasible functional measure for patients with ankylosing spondylitis.

KEY WORDS: Ankylosing spondylitis, Italian version, Revised Leeds Disability Questionnaire, Validation, Disability


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Ankylosing spondylitis (AS) is a chronic inflammatory disease that may progress to bony ankylosis of the entire spine. It requires a combination of pharmacological therapy and rehabilitation programmes.

Many valid instruments to evaluate function and disability have been successfully developed in recent years, such as the Bath Ankylosing Spondylitis Functional Index (BASFI), the Bath Ankylosing Spondylitis Metrology Index (BASMI) and the Dougados Functional Index [1–3].

In 1994 the Revised Leeds Disability Questionnaire (LDQ) was developed and validated as a self-administered questionnaire for the assessment of specific disability in AS [4]. Four categories of response were available, as in the Stanford Health Assessment Questionnaire (HAQ) [5], and LDQ was similarly scored, providing a range of scores from 0 to 3. The questionnaire was found to be acceptable, understandable and easy to complete and it fulfilled recognized criteria for reproducibility and validity.

The LDQ was used as an instrument to measure the functional ability and outcome in patients with AS in different countries and a few years ago a validated Swedish version of the LDQ was developed [6]. In the Swedish language it also seemed to be a reliable tool to investigate function and disability for patients with AS. Moreover, recently the LDQ was compared with the BASFI with the aim of measuring disability in AS; both instruments were able to provide a unidimensional measure of function in patients with AS [7]. The LDQ has also been reported among the validated AS measures to assess patients' outcomes [8].

The purpose of this study was to produce an Italian version of the LDQ and to examine the psychometric properties of this version using (i) internal consistency, (ii) external validity, by comparison with the Italian version of the HAQ and anthropometric measures, and (iii) test–retest, using the intraclass correlation coefficient (ICC).


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Patients
This was a multicentre study involving three Italian rheumatology units. Sixty patients affected by AS were enrolled (50 males, 10 females, mean age 46.1 ± 14.2 yr, range 22–74). The diagnosis of AS was based on the revised New York criteria [9]. The disease's median duration was 4.5 yr (range 1–24). The study was carried out at the out-patient clinics for patients with AS or during a 3-week intensive in-patient admission for rehabilitation, in order to include a broad spectrum of the disease. All patients gave their written informed consent and the study protocol was approved by the local ethics committee. Consent was obtained with a pre-administered letter emphasizing the anonymous and confidential nature of each question.

All patients were invited to fill in the questionnaire as a self-administered one and to return it to the nurse or to the physiotherapist when it was completed. Patients recruited were keen to take part in the validation study.

Thirty of the participants, randomly chosen, were invited to complete the questionnaire again after a 10-day interval.

Translation
Two rheumatologists (E.L., M.A.C.) translated the questionnaire from English to Italian as a first draft; then they sent it to two native English speakers with good knowledge of Italian but without any knowledge of either questionnaire (the original in English and the Italian one) for their revision. They also back-translated the Italian version of the questionnaire and no significant cultural adaptations were made.

LDQ questionnaire
The LDQ is an instrument to measure physical function and disability in patients with AS. It is a self-administered questionnaire including four categories of response, and like HAQ, it was scored from 0 = no difficulty, to 3 = unable to do it. Four areas of function (mobility, bending down, reaching up and neck movements, and posture) are evaluated with four questions in each category (total number of questions = 16) (see supplementary data, available at Rheumatology Online).

Respondents were asked to indicate their level of ability during the previous week. Each individual item was scored 0–3 and within each section the highest score was recorded. Section scores were added and the total score was divided by the number of sections answered, giving an overall score between 0 and 3. Higher scores reflect greater disability.

HAQ questionnaire
The assessment of functional impairment was also collected with this instrument in all patients recruited. HAQ is the most frequently validated scale used for measuring disease-specific physical disability among patients with rheumatic disease. The HAQ has been translated into many languages and an Italian version was validated some years ago [10]. It consists of 20 items divided into eight categories: dressing and grooming, arising, eating, walking, personal hygiene, reaching, gripping, and other activities. Each item is rated from 0 to 3, with 0 = no difficulty and 3 = unable to do, and the highest score within a category is used as the category score.

Anthropometric measures
Cervical spine movements were measured in three planes using a 360° goniometer, with a wide (10 cm) base [11]. Tragus-to-wall distance was the mean distance between right and left sides. Chest expansion was measured at the level of the xiphisternum [12]. Lumbar movement was assessed with (i) a modified Schober's test in flexion and extension using distraction 15 cm apart, the upper 10 cm above and the lower 5 cm below the lumbosacral junction, and (ii) lateral flexion measuring the separation of 10 cm marks placed along the midaxillary line with the upper mark at the level of the xiphisternum [13]. Finger-to-floor distance was measured with a steel ruler from the fingertips to the floor without warm-up.

All measurements were carried out in the early afternoon to avoid morning stiffness, with the help of a senior physiotherapist trained in the rehabilitation of rheumatic disorders, when available.

Statistical analysis
Internal consistency was assessed with Cronbach's {alpha} coefficient.

The external validity of the questionnaire was assessed by comparing the LDQ score with the gold standards taken into account (i.e. the Italian HAQ score and the anthropometric measurements), using Spearman's correlation.

The test–retest reliability was evaluated with a 10 day interval between measurement points and was investigated by computing the ICC.

Statistical analysis was carried out using the SPSS package (version 11.5).


    Results
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
All patients carried out the validation study. All demographic data and the LDQ total score are reported in Table 1. The median value for the total LDQ score was 1.5 (range 0–3), while the median value for the categories mobility, bending, and neck movements were 2 and that for posture was 1.5 (range 0–3). The median value of the total score of the HAQ was 1 (0–3).


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TABLE 1. Demographic, clinical data and LDQ scores of the recruited patients

 
Internal consistency was evaluated with Cronbach's {alpha} coefficient. The overall LDQ was internally consistent ({alpha} = 0.90).

In testing the external validity by comparison of the questionnaire with the HAQ and anthropometric measures, the LDQ score showed a good correlation with HAQ ({rho} = 0.841, P<0.01). Moreover, when single items of the LDQ were compared with the HAQ score a correlation coefficient ranging from 0.67 to 0.72 was observed throughout. When comparing the LDQ with anthropometric measures, a good correlation was observed between the score and the single measures taken into account. Table 2 reports all the correlations computed. In particular, the functional measurements regarding neck movement and reaching up showed a strong correlation with the cervical measurements, and the item regarding mobility did not show any significant correlation with lumbar side flexion, due to a small influence of this movement on the functional score. On the other hand, no correlation was found between the item neck movement and finger-to-floor distance, but this is not surprising because neck movements and reaching up are not correlated with lumbar movements. Moreover, the ‘bending down’ questions showed a good correlation with all anthropometric measurements, indicating the good construct validity of the questionnaire.


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TABLE 2. Correlation with Spearman's correlation coefficient ({rho}), between LDQ functional scores and anthropometric measurements

 
Thirty patients completed the questionnaire again after a 10 day interval and the test–retest reliability showed a good ICC (0.97; 95% confidence interval 0.94–0.98).

Interestingly, LDQ showed a good linear correlation with the disease duration (Spearman's {rho} = 0.556, P<0.01).


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
This study aimed to validate in Italian the LDQ, a useful instrument to assess physical function and disability in patients with AS. The LDQ was developed and validated for the assessment of specific disability in AS and it was found to be acceptable, understandable and easy to complete, fulfilling recognized criteria for reproducibility and validity [4]. Then, the LDQ was used as an instrument to measure the functional ability and outcome in patients with AS [14, 15]. The LDQ was also investigated as a disease-specific measure of health outcome in AS and it was deemed an acceptable and reliable instrument [16]. Finally, it was reported among the AS measures in a review of all validated instruments to define patient outcomes [8].

Most of the questionnaires designed as disease-specific health outcomes in conditions like AS are unidimensional, and a multidimensional approach to evaluate disability has been recommended recently [17]. In fact, LDQ has been shown to address physical function and disability as domains of disease impact, and when it was recently compared with the BASFI questionnaire it showed a unidimensional measure of function with a floor effect [7].

In our study the LDQ score was compared with two gold standards, namely the Italian version of the HAQ and some anthropometric measurements. The choice of the HAQ as a comparator may not have been ideal: in fact an AS-specific instrument, such as BASFI or the Dougados functional index, would have been more appropriate. When the present study was carried out no AS-specific instrument had been translated into the Italian language. However, the HAQ questionnaire is the most frequently validated scale used for measuring disease-specific physical disability among patients with rheumatic diseases. It was developed to assess disability resulting from impairment of peripheral joints in diseases such as rheumatoid arthritis. It was designed for groups of functional limitations of the lower and upper extremities, but it might be less responsive to change than other instruments, especially among individuals with very low or very high levels of disability [18]. Therefore, with the aim of assessing function in diseases that predominantly affect the axial skeleton, such as AS, which may produce a different range of disability, the LDQ was eventually developed. A few years ago, a Swedish version of the questionnaire was validated and it also seemed to be, in the translated language, a reliable tool to investigate function and disability for patients with AS [6].

Moreover, anthropometric measurements have been demonstrated to be useful instruments to evaluate the effectiveness of rehabilitation programmes in AS and to measure outcome in long-term clinical trials [19, 20]. Therefore, these measurements were adopted for the validation study and they showed a strong correlation with the questionnaire.

In this paper we have shown the results of a validation study of the questionnaire translated into a different language. A good correlation with HAQ score was recorded, either with the global score of the LDQ or with single items. Moreover, the Italian LDQ showed a good correlation with anthropometric measurements, either as a global score or as single categories.

The Italian LDQ did not require any major cultural adaptation in the translation process and in many cases a simple literal translation was necessary. It was easy to understand by the patients and quick to complete. In fact, many questions such as those about bending down (‘putting on and taking off your socks’, ‘cutting your toenails’) and those about reaching up and neck movements (‘looking both ways before crossing the road’ and ‘drinking from a small glass or can’) were found very appropriate by the patients, reflecting the potentially severe impairment related to the disease. In other words, this confirms that also the Italian LDQ was able to assess physical function and disability in AS.

Finally, we correlated the LDQ score with the disease duration and we found a strong correlation, showing how the questionnaire reflects the natural course of the disease and showing that a longer disease duration is associated with greater disability.

Our results show that the Italian LDQ is a valid instrument to measure function and disability in AS patients, even when translated.


    Acknowledgments
 
We would like to thank Miss Zoe Waring and Miss Lisa Long for their kind help in the translation.

The authors have declared no conflicts of interest.

Supplementary data

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    Supplementary data are available at Rheumatology Online.


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 

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Submitted 16 December 2004; revised version accepted 14 January 2005.



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