Background: To identify the factors associated with a higher risk of inappropriate days of stay.
Material and method: Crude and adjusted inappropriateness rates were calculated using negative binomial regression to obtain information about the relative risk of each variable. The Appropriateness Evaluation Protocol (AEP) was applied to collect information about patients' hospital stays.
Results: A total of 34.17% (95%CI, 33.28-35.08) of the stays were inappropriate. Women, age older than 65 years, elective admission, and stays in medical services showed the highest inappropriateness risk. Lack of correct patient follow-up in the medical record increased the risk of inappropriateness to 36%.
Conclusions: Lack of continual registration of the patient's clinical course increased the risk of inappropriate days of stay in the hospital. The use of the negative binomial is a valid and simple option for analysis of this type of phenomenon.