Validity of a Venezuelan version of the Bath Ankylosing Spondylitis Functional Index and Bath Ankylosing Spondylitis Disease Activity Index

Introduction: Spondyloarthropathies (SpA) are disabling diseases with a prevalence of 1.9% in the general population. The indices designed for monitoring the disease should be valid, reliable and cross-culturally adapted for decision-making concerning the appropriate treatment. Changing an adjective or pronoun in a self-administered questionnaire could be the big difference in condensing an idea in a few words and transmitting that concept to all those who share the same language. Objectives: To develop a Venezuelan version of the original English version of the BASDAI/BASFI and to evaluate its reliability and validity in Venezuelan patients with SpA. Methods: Certified linguists were needed for the translation of a Venezuelan version of the BASDAI/BASFI. The evaluation of reliability and validity was performed by calculating correlation coefficients in addition to Cronbach's alpha correlation between the BASDAI score and the clinical parameters (for example: erythrocyte sedimentation rate, C-reactive protein, modified Schöber test, occiput-to-wall distance and enthesis count). Results: We studied 40 patients including 31 men (77.5%) and 9 women (22.5%). The mean age was 35.9 years ± standard deviation (SD) 12.01 and the disease duration was 11.5 years (± SD 9.5). The most common diagnoses were undifferentiated spondyloarthritis (45%), ankylosing spondylitis (27.5%) and psoriatic arthritis (20%). The incidences of reactive arthritis, ankylosing spondylitis and juvenile Reiter's syndrome were 2.5% each. The test-retest reliability of the BASDAI and BASFI was high (R = 0.99 and 0.99, respectively; P<.0001). The internal consistency for the BASDAI was high (Cronbach's alpha = 0.88; P=.002) and the intraclass correlation coefficient for internal consistency: 0.9867 (P=.001). Internal consistency for the BASFI: Cronbach's alpha = 0.7985 (P=.002), intraclass correlation coefficient for internal consistency: 0.9055 (P=.001). Construct validity of the BASDAI was high for general well-being of the patient (R = 0.84) and for enthesis count (R = 0.84). Low back pain showed moderate correlation with BASDAI (R = 0.69; P<.0001) and the erythrocyte sedimentation rate showed a low correlation (R = 0.39683; P=.0112). Conclusion: The Venezuelan version of the BASDAI/BASFI could be used in clinical research to assess and evaluate the course of disease activity in Venezuelan SpA patients.