Patients' assessment of quality of life instruments: a randomised study of SIP, SF-36 and SEIQoL-DW in patients with amyotrophic lateral sclerosis
Introduction
Quality of Life (QoL) is now regarded as a fundamental goal of medical care [15]. In amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of the motor system leading to progressive weakness of voluntary muscles and death within 3 years [36], the evaluation of this parameter plays an increasingly important role in clinical research, drug trials [9], [24], and palliative care [7]. However, most of the QoL scales employed so far are heavily weighted toward functional status [32], thus confronting ALS patients with their progressive loss of function. Traditional, so-called “health-related” QoL questionnaires are also frequently based on a fixed, external, health-based value system [16] and may therefore not reflect the patients' individual QoL accurately [12], [17]. In our clinical experience such questionnaire-based scales may actually impart considerable distress to patients with ALS. Two typical representatives of these health-related QoL instruments are the Sickness Impact Profile (SIP) [4] and the Short Form-36 (SF-36) [40]. The SIP has been frequently used in ALS drug trials [3], [5], [6], [21], while the SF-36 was the main outcome measure in a recent European collaborative study on QoL of ALS patients and carers [19].
In the last decade a new approach to QoL assessment was developed which focuses on the individual aspect of QoL, the Schedule for the Evaluation of Individual QoL - Direct Weighting (SEIQoL-DW) [18]. This instrument, which has been validated in a number of patient populations and healthy subjects [11], [18], [34], [39], allows the patients to name and rate, from their own perspective, the areas of life which are most important to their overall QoL.
In order to identify patients' preferences concerning these different approaches to QoL measurement, we performed a randomised trial of SIP, SF-36 and SEIQoL-DW in patients with ALS, asking the patients themselves to evaluate the scales in terms of subjectively perceived validity and distress.
Section snippets
Patients and methods
Patients with a probable or definite diagnosis of ALS according to the El Escorial criteria [10] referred consecutively to the Motor Neuron Outpatient Clinic of the Department of Neurology, Ludwig-Maximilians-University, Munich, Germany between April 1998 and May 1999 were asked to participate in the study. All participants had to meet the following criteria: fluency in German or English, absence of dementia, ability and willingness to come to our clinic every 2 months, absence of serious
Demographic data
Out of 62 eligible patients, 51 (82%) agreed to take part in the study and gave their informed consent. Nine patients (18%) did not complete the study due to death, withdrawal of consent and progression of disease. Study completion (at least three assessments at two-monthly intervals) was achieved by 42 patients (21 each in the SIP/SEIQoL-DW and the SIP/SF-36 subgroups). In 24 cases it was possible to perform five or more assessments (analysis of longitudinal data is forthcoming). The
Discussion
In this study, patients with ALS were asked to complete QoL assessments with the SIP and either the SF-36 or the SEIQoL-DW, and to then rate each of the instruments in terms of subjectively perceived validity and emotional distress inflicted by the completion of the scale. The data show that the SEIQoL-DW is considered to be significantly more valid than either SIP or SF-36. The SIP was found to impart significantly more emotional distress to patients than the SEIQoL-DW and (in one visit) the
Acknowledgements
We thank S. Clarke for helpful comments and Dr. P. Kolyschkow for assistance with the statistical analyses. Our warmest thanks go to our patients for their willingness to participate in the study.
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Present address: Department of Neurology, Ernst-Moritz-Arndt-University, Greifswald, Germany.