Cross-cultural adaptation and assessment of the reliability and validity of the Core Outcome Measures Index (COMI) for the Brazilian-Portuguese language

Abstract

Purpose The use of patient-orientated questionnaires is of utmost importance in assessing the outcome of spine surgery. Standardisation, using a common set of outcome measures, is essential to aid comparisons across studies/in registries. The Core Outcome Measures Index (COMI) is a short, multidimensional outcome instrument validated for patients with spinal disorders. This study aimed to produce a Brazilian-Portuguese version of the COMI. Methods A cross-cultural adaptation of the COMI into Brazilian-Portuguese was carried out using established guidelines. 104 outpatients with chronic LBP ([3 months) were recruited from a Public Health Spine Medical Care Centre. They completed a questionnaire booklet containing the newly translated COMI, and other validated symptomspecific questionnaires: Oswestry Disability Index (ODI) and Roland Morris disability scale (RM), and a pain visual analogue scale. All patients completed a second questionnaire within 7-10 days to assess reproducibility. ResultsThe COMI summary score displayed minimal floor and ceiling effects. On re-test, the responses for each individual domain of the COMI were within 1 category in 98% patients for the domain 'function', 96% for 'symptom-specific well-being', 97% for 'general quality of life', 99% for 'social disability' and 100% for 'work disability'. The intraclass correlation coefficients (ICC 2,1 ) for COMI pain and COMI summary scores were 0.91-0.96, which compared favourably with the corresponding values for the RM (ICC, 0.99) and ODI (ICC, 0.98). The standard error of measurement for the COMI was 0.6, giving a ''minimum detectable change'' (MDC95%) of approximately 1.7 points i.e., the minimum change to be considered ''real change'' beyond measurement error. The COMI scores correlated as hypothesised (Rho, 0.4-0.8) with the other symptom-specific questionnaires. Conclusions The reproducibility of the Brazilian-Portuguese version of the COMI was comparable to that of other language versions. The COMI scores correlated in the expected manner with existing but longer symptom-specific questionnaires suggesting good convergent validity for the COMI. The Brazilian-Portuguese COMI represents a valuable tool for Brazilian study-centres in future multicentre clinical studies and surgical registries.

Cross-cultural adaptation and validation of the Polish version of the Core Outcome Measures Index for low back pain

“…Just one COMI item ''work disability'' exceeded the ideal range of \15-20 % [1,20,21]. Similar findings have been reported in the French [12], Norwegian [14] versions, Brazilian-Portuguese [13] and Italian [1] had even higher rates of ceiling effect also for the ''social disability'' item. This lower proportion of more ''healthy'' patients in our study can be explained by the high ratio of surgical candidates included.…”

“…The floor effect was more prominent and affected three items: ''symptom-specific well-being'', ''social disability'' and ''work disability''; however, none of the values exceeded 70 %-the value considered adversely affecting the results [1,13,19]. High ratio of floor effect for the ''symptom-specific well-being'' was also noted for French [12], Brazilian [13] and Norwegian [14] versions. Relatively high values for the ''social disability'' and ''work disability'' were also reported in the French [12] version.…”

“…In such situation, no significant deterioration or improvement of their disability can be detected [1,13]. Floor and ceiling effects [70 % are considered to be adverse for the study [1,13,19] and \15-20 % ideal [1,20,21]. Floor and ceiling effects for all core items of COMI were evaluated.…”

“…The possible values for ICC are within the range 0.00-1.00; values of 0.60-0.80 are considered to indicate good reliability and above 0.80 excellence [23]. Standard error of measurements (SEM agreement ) was used to establish the absolute measurement error [13,24] and to calculate the minimum detectable change (MDC 95% ) for the evaluated questionnaire. The MDC 95% indicates the minimum change of score considered by patient a ''real change'', greater than the instruments' measurement error [25].…”

“…The psychometric properties of COMI have been assessed by several independent research groups [6][7][8][9][10], proving it to be a valid and highly responsive instrument. It has been adapted and validated for the use in German [8,11], Spanish [7], French [12], Italian [1], Brazilian-Portuguese [13] and Norwegian [14] versions. Analogous version of COMI for patients with neck pain and related disorders was developed, adapted and validated for use in German [15] and English [9] versions.…”