Development of an Adherence to Anticoagulant Therapy Scale: A Validity and Reliability Study

Purpose: Anticoagulants are an important group of drugs used by many patients with different diseases. There are general adherence scales that measure adherence to treatment in the literature. However, the correct use of the drug alone is not sufficient for adherence with warfarin therapy. To develop Anticoagulant Therapy Adherence Scale for use in patients on warfarin and to examine psycholinguistic and psychometric properties. Methods: The research was of a methodological and consisted of 170 patients. The validity of the scale was tested by using content validity, explanatory and confirmatory factor analysis. The reliability of the scale was examined by utilizing item-total scale correlations and Cronbach’s alpha. Results: After the scale items were created, opinions were received from twenty experts and content validity indexes were found to be above 0.80. In the explanatory factor analysis, a 3-factor structure with factor loads between 0.30 and 0.81 was obtained. Fit indices obtained in the confirmatory factor analysis were as follows: χ2 = 181.116, df = 116 χ2/df value 1.561, Root Mean Square Error of Approximation (RMSEA) = 0.058, Comparative Fit Index (CFI): 0.88 and Goodness Fit Index (GFI): 0.88. Item-total scale correlation coefficients were found to range between 0.57 and 0.25. The Cronbach's alpha reliability coefficient was 0.74 for the overall scale and 0.63, 0.77 and 0.65 for its subscales. Conclusions: ATAS was found to be a valid and reliable measurement tool in Turkish population. The scale can be used by healthcare professionals to evaluate patients' use of warfarin in a standard way.