The influence of missing components of the Acute Physiology Score of APACHE III on the measurement of ICU performance.
OBJECTIVE
To determine the impact of missing Acute Physiology Score (APS) values on risk-adjusted mortality.


METHODS
Retrospective review of prospectively collected Acute Physiology and Chronic Health Evaluation (APACHE) III database.


METHODS
The intensive care units (ICUs) of an academic medical center.


METHODS
38,411 patients admitted to ICU between October 1994 and December 2003.


RESULTS
Data were collected on ICU type, missing first ICU day APS values, predicted and observed hospital mortality, standardized mortality ratio (SMR), 95% confidence interval (CI), odds ratio (OR). The overall observed and predicted hospital mortality rates were 8.7% and 10.8%, respectively, with SMR of 0.806 (95% CI 0.779-0.834). Complete data were available in 829 (2.2%). Vital signs were missing in almost none and serum albumin and bilirubin in over 80% of the patients. The number of missing variables was higher in less sick and surgical ICU patients. Logistic regression analysis showed that the risk of dying in the hospital was significantly associated with the number of missing APS variables (OR 1.058, 95% CI 1.027-1.090) when adjusted for the severity of illness. The risk of death was also associated with the type of missing variables.


CONCLUSIONS
Since missing APS values may lead to underestimation of the predicted mortality rates, the number and type of missing variables should be taken into consideration when assessing the performance of an ICU. Unless data collection is standardized, future prognostic models should use variables that are routinely measured in most critically ill patients without sacrificing statistical precision.
Afessa
Bekele
B
Division of Pulmonary and Critical Care, Department of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Afessa.Bekele@mayo.edu
Keegan
Mark T
MT
Gajic
Ognjen
O
Hubmayr
Rolf D
RD
Peters
Steve G
SG
D018806:APACHE; D004282:Documentation; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000592:standards*; D007591:Joint Commission on Accreditation of Healthcare Organizations; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D011787:Quality of Health Care; D012189:Retrospective Studies; D014481:United States