The Attributable Burden and Costs of Infections Caused by Antibiotic-Resistant Gram-Negative Bacteria in Dutch Hospitals

This study addresses the following three aims:

1. To provide a more accurate estimate than currently available of the incremental disease burden and attributable costs of antibiotic-resistant as compared to antibiotic-sensitive gram-negative bacteria (i.e. Enterobacteriaceae and non-fermenters). This analysis is focused on gram-negative infections for which patients are hospitalized. In a less detailed manner, the same analysis of disease burden and costs can be performed for acquiring a gram-negative infection during hospitalization.
2. To identify determinants associated with resistance in gram-negative infections, to the extent that they are confounders of the relation between resistance and outcome.
3. To adapt and optimize existing methodology to measure the burden of resistance, among others by calculating disability-adjusted life years (DALYs) which incorporate not merely mortality, but also morbidity.

GRAND-ABC is designed as a prospective parallel matched cohort, which will run for a year in each of the eight participating hospitals. The primary cohort is a random sample of all Gram-negative infections occurring in a participating hospital during the study period. This cohort can be divided on the basis of the primary determinant status (whether the Gram-negative pathogen is resistant or not based on Dutch guideline for multi-drug resistant organisms; Werkgroep Infectiepreventie (WIP). Bijzonder resistente micro-organismen (BRMO). December 2012. http://www.wip.nl/free_content/Richtlijnen/130424_BRMO.pdf) into two parallel subcohorts. Each patient in each of the subcohorts will be matched to one patient without a gram-negative infection. Together these will form the secondary cohort of non-infected patients: patients admitted to the hospital during the study period who are within the same risk set as the infected patients.

For all patients data collection will be performed by review of medical files, which will cover the entire admission during which they were included in the study, and all cause 30 day mortality. Data collection for the hospital stay covers confounders and effect modifiers of the associations studied, and feeds into the outcomes costs, DALYs and length of stay. For the cohort with gram-negative infections, data on infection parameters and antibiotic treatment parameters are also collected.

In addition, the subcohort with infections by multi-drug resistant organisms and a random 20% of the subcohort with infections by sensitive organisms will be selected for follow-up, consisting of sending questionnaires and renewed medical file review 30 days after the index culture date. In the case of ongoing sequelae of the gram-negative infection, this procedure is repeated 90 days after the index culture date. These questionnaires will feed into the outcomes costs, DALYs and quality-adjusted life years (QALYs).