The study convincingly validates the OPTIMAL-confidence scale; however, the high percentage of “not applicable” responses for items like squatting, kneeling, and bending raises concerns about the questionnaire’s comprehensiveness across diverse patient profiles. Could the authors elaborate on how these missing responses were accounted for in the analysis and whether they considered adapting the questionnaire to accommodate varying functional capacities? The study focuses predominantly on primary care settings in Spain; could the findings differ in populations with distinct cultural or healthcare contexts?
The comment raises relevant points regarding the comprehensiveness and applicability of the OPTIMAL-confidence questionnaire. My understanding is that the high percentage of “not applicable” responses for items such as squatting, kneeling, and bending may reflect functional limitations specific to the chronic low back pain population included in the study. These responses might have been addressed through statistical techniques, such as imputation or sensitivity analysis, to ensure they did not bias the overall validation results. Additionally, while the study was conducted in primary care settings in Spain, the psychometric methods used appear robust and could potentially be generalized to other cultural or healthcare contexts with minor adaptations.
Could the authors clarify whether adjustments for “not applicable” responses were applied and if cross-cultural validation efforts are planned or feasible?