[Translation, cross-cultural adaptation, and content validity of the Taxonomy of the Measurement Properties and the COSMIN Risk of Bias Tool for Brazil].

The absence of Brazilian Portuguese versions of the Taxonomy of Measurement Properties and the COSMIN Risk of Bias Tool limits the standardization of methodological evaluations in studies on reliability and measurement error in Brazil. This research aimed to translate, cross-culturally adapt, and evaluate the content validity of these tools for Brazil. This methodological study was conducted according to international guidelines. It included independent double translation, synthesis, back-translation, technical appreciation by the COSMIN team, and expert evaluation via two-round modified Delphi. Content validity was examined using a quantitative (item content validity index - I-CVI, and content validity coefficient - CVC) and qualitative approach (based on its relevance, comprehensiveness, and comprehensibility). In total, six experts participated in the first round and five in the second. In the first round, the I-CVI found problems of clarity, whereas the CVC detected a greater number of items in need of revision. Main adjustments involved statistical terminology, textual standardization, and writing simplification. After the revisions, all items reached acceptable values in the second round. The final mean CVC totaled 0.915 for the Taxonomy of Measurement Properties and 0.934 for the COSMIN Risk of Bias Tool. The Brazilian Portuguese versions of both tools showed satisfactory evidence of content validity, with adequate clarity, relevance, comprehensiveness, and comprehensibility. These versions provide a standardized methodological basis for evaluating studies on reliability and measurement error in the Brazilian context.