Knee osteoarthritis pre-screening questionnaire (KOPS): cross-cultural adaptation and measurement properties of the brazilian version-KOPS Brazilian version

Background Despite the criteria already established for the classification of knee osteoarthritis (OA), a radiographic and/or clinical knee OA diagnosis usually occurs in cases of fully manifest or more advanced disease, which can make health promotion, prevention, and functional rehabilitation in more advanced stages of the disease less effective. In addition, radiographic knee OA can generate more financial costs for health services. Therefore, developing and validating screening instruments to assess the probability of development and progression of knee OA would be of great value for both clinical practice and science. Objective To cross-culturally adapt and investigate the measurement properties of the Knee OA Pre-screening Questionnaire Brazilian version. Methods A total of 250 individuals of both sexes aged between 35 and 92 years [(mean (standard deviation): 63 (11) years old; 74.1 (15.1) kg; 1.59 (0.09) m; 29.38 (5.44) kg/m(2)] participated in this study. The cross-cultural adaptation and analyses of the measurement properties of the KOPS Brazilian version included: (1) assessment of conceptual and item equivalence; (2) assessment of semantic equivalence; (3) assessment of operational equivalence; and (4) assessment of measurement equivalence, reliability, and validity. Results Cronbach's alpha for the internal consistency among the six components of the KOPS Brazilian version was 0.71. The test-retest 72 h apart for each component resulted in a coefficient correlation intraclass ranging from 0.74 to 1.00. The probability of an individual randomly chosen from the population having KL >= 1 and KOPS Brazilian version >= 21 points was 0.74 (area under the curve of the Receiver Operating Characteristic - AUC of ROC); furthermore, the AUC for KL >= 2 and the KOPS Brazilian version >= 23 points was 0.77. Conclusion The KOPS Brazilian version is a reliable and valid instrument for early screening of knee OA in individuals aged 35 years and over in the Brazilian context.