All patients in a Norwegian tertiary care university hospital were screened for hospital
acquired infection (HAI) on six dates during 2005 and 2006. The hospital costs for all patients
were estimated according to a national standard. A total of 159 patients with HAI and 2689
control patients were identified. The median hospital cost for HAI patients was found to be
NOK 381 716 (EUR 45 547) compared to NOK 153 512 (EUR 19 122) for controls.
The excessive costs for patients with HAI were most pronounced in the second and third cost
quartiles. In the fourth quartile, calculated hospital costs were lower for patients with HAI
compared to controls. However, the uncertainty of the cost calculation increased with rising
hospital cost. Median length of stay (LOS) was 20 days and three days respectively, but
median LOS before appearance of HAI was six days, suggesting that the two groups of
patients were not directly comparable. This was corroborated by the diagnosis related groups
(DRG) weights which were 2.5 times higher among patients with HAI. When patients with
LOS shorter than four days were excluded from the analysis, the cost difference between the
two groups was eliminated.