Studies have shown the importance of including the user's experience in measuring the usability of medical devices. Still, the user's assessment depends on the context of use for the treatment received. To measure the usability in such a way as to separate these effects and understand the sources affecting users' perceptions, the article proposes an analytical strategy that assesses the effect of the context of use on measuring the device's usability. Next, we create indicators that are free of these effects to understand the overall assessment of the device. Multivariate analysis of variance and exploratory factor analysis are used to achieve the objectives. The study is illustrated by means of a survey of 200 hemodialysis patients in hospitals and clinics in Porto Alegre, Rio Grande do Sul State, Brazil. The results suggest that assessment of the medical device differs (p < 0.05) according to the setting, fistula site, and patient's sex, age, and schooling. The setting influenced the most variables, including the degree of trust in the procedures. Three indicators were created: procedures, treatment setting, and device characteristics. The indicators allowed assessing which equipment brands, types of procedures, and treatment settings provide the best results. The method can be replicated in the assessment of medical devices, training health administrators, and assessing usability through summary indicators, besides identifying aspects to improve usability in medical treatment.