Abstract
Background
The main French language scales evaluating functioning after lower-limb amputation have not undergone exhaustive psychometric validation.
Objective
A transcultural validation of the Special Interest Group in Amputee Medicine (SIGAM) mobility grades questionnaire, with 21 closed questions, as an administered questionnaire.
Methods
The questionnaire translation, back-translation and original-author validation was followed by a pretest with 5 patients to check comprehension. The psychometric properties of the scale were validated with 49 patients at the definitive prosthesis stage by an investigator via telephone. Criterion validity was evaluated by comparison with the Houghton Scale score and construct validity by correlation between the questionnaire scores and convergent dimensions (performing everyday activities and performing transfers on a numerical rating scale [NRS], 2-min walk test) and divergent dimensions (managing medication and stump skin care on an NRS). Internal consistency was assessed by the Kuder–Richardson Formula 20 (KR-20) coefficient and test–retest reproducibility by the Cohen kappa coefficient.
Results
The resulting questionnaire was validated by the original author after the back-translation. It showed good psychometric properties when administered by an investigator as a self-reporting questionnaire, excellent criterion validity ( r = 0.89, P < 0.01), excellent reproducibility (kappa coefficient 0.87) and satisfactory construct validity. The KR-20 coefficient was 0.67.
Conclusion
The French version of the SIGAM mobility grades questionnaire (SIGAM-Fr) has satisfactory psychometric properties and can be administered in clinical practice.
1
Introduction
Major amputation of the lower limb(s) is a health problem in many countries: in France, 4202 trans-femoral amputations and 3640 amputations at the knee or trans-tibia were performed in 2007 . The estimated incidence of all-cause amputations is 1.4/10,000 people in Brazil and 3.4 and 1.7/10,000 people for men and women, respectively, in the United States . The profile of patients undergoing lower-limb amputations has evolved, with amputations for vascular disease predominant , mainly in older frail patients, who require personalised program in terms of interventions and surveillance because of their potential comorbidities (mood status, cardiac impairment). Beyond these physical aspects, the participation of amputees in everyday life activities may be restricted depending on their psychological state, environmental factors, and prosthesis-related aspects.
The choice of the prosthesis depends on the patient’s objectives, especially the possibility of walking and its quality, which is a crucial element for autonomy and quality of life. The evaluation of walking ability is thus essential to achieve optimal management during rehabilitation.
We have many ways to evaluate deficiencies and limitations of activity resulting from amputation (locomotion problems, difficulties in performing transfers [e.g., from bed to wheelchair], etc.). Clinical tests used for evaluations include balance tests and standardized walking tests (e.g., 2-min walk test, get-up-and-go test). These tests can be refined by instrumental evaluations (stabilometry, quantified gait analysis) that provide objective quantitative data resulting from specialised professional and technological resources, which are often time-consuming and expensive. Other evaluations involve questionnaires and scales. Such tools are subjective but are easy to administer in routine clinical practice, as a self-reporting or administered questionnaire. Certain generic questionnaires are available (e.g., Barthel index, Functional Independence Measure) but are of limited use because they are not specific to lower-limb amputees .
Questionnaires that are specific to functional limitations in amputees fitted with a prosthesis have shown good metrological qualities . However, only 2 have been validated in French: the Houghton Scale and the Prosthetic Profile of Amputees. The Houghton Scale is an administered questionnaire in which walking ability carries considerable weight . It can be used to evaluate the results of prosthetic fitting by considering use of the prosthesis, walking outside and stability of the patient on different surfaces. This scale has been validated in French, even though its criterion validity was moderate as compared with the Barthel index . The Prosthetic Profile of the Amputee is a global questionnaire that takes into account patients’ physical condition, satisfaction, use of the prosthesis, and interactions with the physical and social environment. This questionnaire features good validity and satisfactory reproducibility in French. It also includes a mobility index as a subscale, which aims to objectively analyse the functional capacities of patients with their prosthesis. However, it is time-consuming and difficult to use, which, despite its many advantages, limits its use in everyday clinical practice.
Because these questionnaires provide limited analysis or are too complex for everyday clinical practice, other tools are necessary. A transcultural validation of the Special Interest Group in Amputee Medicine (SIGAM) mobility grades questionnaire may be an alternative . Indeed, this scale, proposed by the British Society of Rehabilitation Medicine, is a self-administered questionnaire comprising 21 closed questions (yes or no responses). It evaluates walking in terms of help from others, walking aids, walking distance and ability to walk on different surfaces and in different meteorological conditions ( Appendix A ). This questionnaire can be analysed simply by using a defined algorithm ( Appendix A ) that provides perfect reproducibility of analysis . This questionnaire also shows good validity as compared with the Timed Walking Test and the Rivermead Mobility Index and good sensitivity to change. Therefore, the scale seems appropriate to obtain an objective clinical description of functional mobility in patients with lower-limb amputation. Given its ability to provide a simple, quick and comprehensive evaluation of functioning and walking for such patients, this detailed self-reporting questionnaire deserves to be translated into French . The transcultural validation of a measurement instrument is a crucial process before its widespread use in international clinical trials . The instrument’s first validation was in Dutch and it has been used in British and Dutch research protocols for evaluating activity limitations for lower-limb amputees.
The aim of this work was to undertake the transcultural translation of the SIGAM mobility grades questionnaire into French, then validate its psychometric properties by investigator administration of the questionnaire.
2
Methods
This was a single-centre prospective study approved by our institutional ethics committee and conformed to the principles outlined in the Declaration of Helsinki. The study was in 2 parts: transcultural translation and transcultural validation. Patients who helped validate the instrument gave their informed oral consent to be in the study.
2.1
Transcultural translation
We followed international recommendations for this type of work . We requested permission to develop a French version of the SIGAM mobility grades questionnaire from the original author of the scale (Dr. N.H. Ryall) and asked him to take part in the instrument validation as an expert. Then, 2 bilingual native French-speaking translators translated the questionnaire into French. One of the translators is a physical medicine and rehabilitation physician and thus knew the concepts measured by the scale. The second does not work in the field of medicine, so the initial translations would not be affected by the medical culture, thus limiting the use of medical terms, which could be ambiguous or incomprehensible to patients. The committee of native French-speaking experts met to compare the 2 translations. Disagreements were resolved by discussion. Then, a bilingual native French-speaking translator, who had not taken part in the first translation and did not know the initial questionnaire, back-translated the questionnaire. This translator was neither a physician nor an expert in the field. The back-translation was presented to the original author of the questionnaire (Dr. N.H. Ryall) to determine whether it agreed with the original questionnaire from a conceptual point of view. Then the questionnaire was tested on a small sample of amputees patients ( n = 5) to assess its feasibility.
2.2
Transcultural validation
2.2.1
Population and protocol
Patients included were consulting at the prosthesis-fitting centre at Dijon CHU following single-limb or double-limb trans-tibial or trans-femoral amputation. We excluded patients < 18 years old, with a prosthesis for < 6 months or recent modification of the prosthesis < 4 months (other than renewal of the socket), who were unable to complete the questionnaire because of cognitive disorders (Mini-Mental State Examination score < 23 ) or had language barriers.
2.2.2
Variables measured
For each patient, we recorded age, sex, level of amputation, reason for the amputation, score on the Hospital Anxiety and Depression Scale (HADS) , the Houghton Scale score and self-evaluation of the following items by a Numerical Rating Scale (NRS) from 0 to 10: performing everyday activities, satisfaction with the prosthesis, performing transfers independently, care of the skin around the stump, managing medication and evaluating phantom pain. The SIGAM-Fr was administered by an investigator by telephone as a self-reporting questionnaire.
2.2.3
Psychometric validation
2.2.3.1
Criterion validity
We assessed the concurrent validity of the SIGAM-Fr score by its correlation with the score for the French version of the Houghton Scale, the reference scale in France, by Spearman’s correlation coefficient.
2.2.3.2
Construct validity
To assess construct validity, we evaluated convergent validity and divergent validity of the attributed grade. To assess convergent validity, we measured correlations between the SIGAM-Fr grades and values for variables that a priori reflected similar dimensions or concepts. For divergent validity, we examined correlations between the SIGAM-Fr grades and values for variables that a priori reflected dimensions or concepts that differed from those evaluated by our questionnaire. Hence, we hypothesized that the SIGAM-Fr score 1 would correlate closely with patient NRS scores for performing everyday activities (0: “inability to practice activities”; 10: “easy to practice activities”), performing transfers (0: “inability to perform transfers”; 10: “perfect performance of transfers”) and performing the 2-min walk test (data from previous consultations) and 2 would not correlate with NRS scores for managing medication (0: “unable to manage medications by self”; 10: “perfect management of medications by self”) and stump skin care (0: “no care of stump skin”; 10: “daily care of stump skin”). We used the NRS because of its ease of use and good understanding by patients. Furthermore, this method allowed us to cover areas not explored by other scales used for lower-limb amputees.
2.2.3.3
Reliability
We analysed the internal consistency of the questionnaire by the Kuder–Richardson Formula 20 (KR-20) because it deals with dichotomous variables (yes or no) and examined its test–retest reproducibility by calculating the Cohen kappa coefficient . Each patient completed the SIGAM-Fr twice at an interval of 2 weeks as an administered questionnaire during telephone interviews with an investigator. Patients were considered lost to follow-up after 3 unsuccessful attempts to contact them by telephone at day 14.
2.2.3.4
Evaluation of confounding factors
We chose several confounding factors that might modify the SIGAM-Fr score. We assessed the correlation between these factors and the SIGAM-Fr score by the Spearman’s correlation coefficient. Confounding factors were NRS scores for phantom pain (0: “permanent phantom pain”; 10: “no phantom pain”) and satisfaction with the prosthesis (0: “not satisfied at all with prosthesis”; 10: “perfect satisfaction with prosthesis”) and the HADS score.
Phantom pain, present in many patients, can have an important role in the mood of these patients. Moreover phantom pain is commonly reduced by the use of the prosthesis. Because mood can modify patient’s walk, we considered it a confounding factor. Satisfaction with the prosthetic material, whether justified or not, determines the use of the prosthesis.
The HADS score is a validated score that measures anxiety and depression. Mood can interfere with the patient’s motivation and induce an incorrect SIGAM-Fr score. The HADS score comprises 14 items scored from 0 to 3. Seven items explore anxiety with a threshold score of 12 and 7 explore depression with a threshold score of 8. The HADS is a self-reporting questionnaire that was administered by telephone by an investigator. To validate the use of the HADS score as an administered questionnaire, we evaluated its test–retest reproducibility at 2-week intervals by calculating the intra-class correlation coefficient (ICC) for patients for whom the reproducibility of the SIGAM-Fr was evaluated as an administered questionnaire.
2
Methods
This was a single-centre prospective study approved by our institutional ethics committee and conformed to the principles outlined in the Declaration of Helsinki. The study was in 2 parts: transcultural translation and transcultural validation. Patients who helped validate the instrument gave their informed oral consent to be in the study.
2.1
Transcultural translation
We followed international recommendations for this type of work . We requested permission to develop a French version of the SIGAM mobility grades questionnaire from the original author of the scale (Dr. N.H. Ryall) and asked him to take part in the instrument validation as an expert. Then, 2 bilingual native French-speaking translators translated the questionnaire into French. One of the translators is a physical medicine and rehabilitation physician and thus knew the concepts measured by the scale. The second does not work in the field of medicine, so the initial translations would not be affected by the medical culture, thus limiting the use of medical terms, which could be ambiguous or incomprehensible to patients. The committee of native French-speaking experts met to compare the 2 translations. Disagreements were resolved by discussion. Then, a bilingual native French-speaking translator, who had not taken part in the first translation and did not know the initial questionnaire, back-translated the questionnaire. This translator was neither a physician nor an expert in the field. The back-translation was presented to the original author of the questionnaire (Dr. N.H. Ryall) to determine whether it agreed with the original questionnaire from a conceptual point of view. Then the questionnaire was tested on a small sample of amputees patients ( n = 5) to assess its feasibility.
2.2
Transcultural validation
2.2.1
Population and protocol
Patients included were consulting at the prosthesis-fitting centre at Dijon CHU following single-limb or double-limb trans-tibial or trans-femoral amputation. We excluded patients < 18 years old, with a prosthesis for < 6 months or recent modification of the prosthesis < 4 months (other than renewal of the socket), who were unable to complete the questionnaire because of cognitive disorders (Mini-Mental State Examination score < 23 ) or had language barriers.
2.2.2
Variables measured
For each patient, we recorded age, sex, level of amputation, reason for the amputation, score on the Hospital Anxiety and Depression Scale (HADS) , the Houghton Scale score and self-evaluation of the following items by a Numerical Rating Scale (NRS) from 0 to 10: performing everyday activities, satisfaction with the prosthesis, performing transfers independently, care of the skin around the stump, managing medication and evaluating phantom pain. The SIGAM-Fr was administered by an investigator by telephone as a self-reporting questionnaire.
2.2.3
Psychometric validation
2.2.3.1
Criterion validity
We assessed the concurrent validity of the SIGAM-Fr score by its correlation with the score for the French version of the Houghton Scale, the reference scale in France, by Spearman’s correlation coefficient.
2.2.3.2
Construct validity
To assess construct validity, we evaluated convergent validity and divergent validity of the attributed grade. To assess convergent validity, we measured correlations between the SIGAM-Fr grades and values for variables that a priori reflected similar dimensions or concepts. For divergent validity, we examined correlations between the SIGAM-Fr grades and values for variables that a priori reflected dimensions or concepts that differed from those evaluated by our questionnaire. Hence, we hypothesized that the SIGAM-Fr score 1 would correlate closely with patient NRS scores for performing everyday activities (0: “inability to practice activities”; 10: “easy to practice activities”), performing transfers (0: “inability to perform transfers”; 10: “perfect performance of transfers”) and performing the 2-min walk test (data from previous consultations) and 2 would not correlate with NRS scores for managing medication (0: “unable to manage medications by self”; 10: “perfect management of medications by self”) and stump skin care (0: “no care of stump skin”; 10: “daily care of stump skin”). We used the NRS because of its ease of use and good understanding by patients. Furthermore, this method allowed us to cover areas not explored by other scales used for lower-limb amputees.
2.2.3.3
Reliability
We analysed the internal consistency of the questionnaire by the Kuder–Richardson Formula 20 (KR-20) because it deals with dichotomous variables (yes or no) and examined its test–retest reproducibility by calculating the Cohen kappa coefficient . Each patient completed the SIGAM-Fr twice at an interval of 2 weeks as an administered questionnaire during telephone interviews with an investigator. Patients were considered lost to follow-up after 3 unsuccessful attempts to contact them by telephone at day 14.
2.2.3.4
Evaluation of confounding factors
We chose several confounding factors that might modify the SIGAM-Fr score. We assessed the correlation between these factors and the SIGAM-Fr score by the Spearman’s correlation coefficient. Confounding factors were NRS scores for phantom pain (0: “permanent phantom pain”; 10: “no phantom pain”) and satisfaction with the prosthesis (0: “not satisfied at all with prosthesis”; 10: “perfect satisfaction with prosthesis”) and the HADS score.
Phantom pain, present in many patients, can have an important role in the mood of these patients. Moreover phantom pain is commonly reduced by the use of the prosthesis. Because mood can modify patient’s walk, we considered it a confounding factor. Satisfaction with the prosthetic material, whether justified or not, determines the use of the prosthesis.
The HADS score is a validated score that measures anxiety and depression. Mood can interfere with the patient’s motivation and induce an incorrect SIGAM-Fr score. The HADS score comprises 14 items scored from 0 to 3. Seven items explore anxiety with a threshold score of 12 and 7 explore depression with a threshold score of 8. The HADS is a self-reporting questionnaire that was administered by telephone by an investigator. To validate the use of the HADS score as an administered questionnaire, we evaluated its test–retest reproducibility at 2-week intervals by calculating the intra-class correlation coefficient (ICC) for patients for whom the reproducibility of the SIGAM-Fr was evaluated as an administered questionnaire.
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