Portuguese version of the standardized Nordic musculoskeletal questionnaire: cross cultural and reliability

Background The self-administered questionnaires are fundamental for clinical assessment and research. The accessibility and constant use of recognized questionnaires in different languages facilitates the compilation of reliable data in international multicentre studies. Aim The purpose of this study was to carry out a cross-cultural adaptation of the standardized Nordic musculoskeletal questionnaire for Portuguese workers and to investigate the psychometric properties of the Portuguese version. Methods Sixty warehouse workers completed the questionnaire booklet containing the newly translated version of the standardized Nordic musculoskeletal questionnaire (NMQ) and the Oswestry disability index (ODI). After a week, to test reliability, all the individuals completed the standardized Nordic musculoskeletal questionnaire for a second time. The study is in accordance with the ERGHO guidelines for cross cultural adaptation. Results The Kendall's tau-b correlation coefficient demonstrated existence of association to the upper back region variable last 7 days (0.350 to p<0.01), low back region variable last 7 days (0.290 to p<0.05), and low back region variable limitations in daily activities (0.479 to p<0.01). These results showed a moderate correlation between the NMQ and ODI. Through the Kappa agreement correlation coefficient, we observe that the majority of the correlation coefficients were between 0.8 and 1, showing the existence of a strong to a very strong association, indicative of good levels for test-retest reliability. The Kuder-Richarson coefficient of reliability showed a correlation coefficient of 0.855 indicative of good internal consistency. Conclusion The Portuguese version of the standardized Nordic musculoskeletal questionnaire for Portuguese workers seems to be valid revealing good coefficients of reliability.