Three methods for estimating days of hospitalization because of hospital-acquired infection: a comparison

The objective of this study is to compare the three methods internationally used for estimating days of hospitalization attributable to hospital infections by applying them to the same population. The methods are: (1) unmatched comparison group; (2) matched control method-based; and (3) Appropriateness Evaluation Protocol method. A study of the prevalence of infections was performed among patients during hospitalization for an ordinary single sampling department. The survey was completed within eight working days between 15 and 24 October 2007. All patients admitted at least 24 hours to the survey day in each department were included in the study, as well as patients discharged/transferred to another hospital or department. During the prevalence study 621 patients were observed, 70 of which with infection (equal to 11.27%).

The 70 uninfected patients needed for comparison using method 1 were selected through a procedure based on propensity score on demographic variables and clinical trials of patients. The Shapiro-Wilk test was used to verify the normality of quantitative variables. In comparing the three methods Kruskall-Wallis test was used (alpha = 0.05), while comparisons between pairs of methods were performed with the Mann-Whitney test (alpha = 0.017).

Estimation results of recovery days with infection using the three comparison tests showed that there is a statistically significant difference between the three methods (P = 0.016) and there is a significant difference between 1 versus 3 (P = 0.013) and between 2 and 3 (P = 0.017), whereas between 1 and 2 no difference was found (P = 0.82).

In conclusion, the three methods are not showing the same estimations and thus may not be exchangeable.