Excess length of hospital stay due to healthcare acquired infections: methodologies evaluation.

Background: Healthcare acquired infections (HAI) cause an increase of burden and in particular excess length of hospital stay (LOS) accounts for approximately up to 90% of total costs. Therefore accurate estimation of extra hospital stay due to healthcare acquired infections is very important.
Methods: The authors carried out a review comparing the principal methods internationally used for estimating the excess LOS attributable to healthcare acquired infections.
Results: The methods described and analysed are: 1) Implicit physician assessment; 2) appropriateness evaluation protocol; 3) unmatched case-control; 4) matched case-control; 5) regression analysis; 6) multistate model. The various methodologies are described underlining advantages and limits which researchers need to know before starting any economic analysis.
Conclusions: Overall, studies taking into account the time-dependent nature of HAI show to give more precise and reliable results.