• Stefan J Cano, Donna L Lamping, Luke Bamber, and Sarah Smith.
• Department of Clinical Neuroscience, Peninsula College of Medicine and Dentistry, Room N16 ITTC Building, Tamar Science Park, Davy Road, Plymouth, Devon, PL6 8BX, UK. stefan.cano@pcmd.ac.uk
• Health Qual Life Out. 2012 Jan 1; 10: 120.

BackgroundThe Anti-Clot Treatment Scale (ACTS) is a 15-item patient-reported instrument of satisfaction with anticoagulant treatment. It includes a 12-item ACTS Burdens scale and a 3-item ACTS Benefits scale. Its role in clinical trials and other settings should be supported by evidence that it is both clinically meaningful and scientifically sound. The aim of the study was to evaluate the measurement performance of the ACTS (Dutch, Italian, French, German and English language versions) in patients with venous thromboembolism based on traditional psychometric methods.MethodsACTS Burdens and Benefits scale data from a large clinical trial (EINSTEIN DVT) involving 1336 people with venous thromboembolism were analysed at both the scale and item level. Five key psychometric properties were examined using traditional psychometric methods: acceptability, scaling assumptions, reliability (including internal consistency reliability, test-retest reproducibility); validity (including known groups and discriminant validity); and responsiveness. These methods of examination underpin the US Food and Drug Administration recommendations for patient-reported outcome instrument evaluation.ResultsOverall, the 12-item ACTS Burdens scale and 3-item ACTS Benefits scale met the psychometric criteria evaluated at both item and scale levels, with the exception of some relatively minor issues in the Dutch language version, which were just below reliability criteria (i.e. alpha = 0.72, test-retest intraclass correlation = 0.79). A consistent finding from item-level evaluations of aggregate endorsement frequencies and skewness suggested that response scales may be improved by reducing the number of response options from five to four.ConclusionsBoth the ACTS Burdens and ACTS Benefits scales consistently satisfied traditional reliability and validity criteria across multiple language datasets, supporting it as a clinically useful patient-reported instrument of satisfaction with anticoagulant treatment in clinical trials.Trial Registration NumberNCT00440193.

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