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A calibration study of SAPS II with Norwegian intensive care registry data
Author(s) -
HAALAND Ø. A.,
LINDEMARK F.,
FLAATTEN H.,
KVÅLE R.,
JOHANSSON K. A.
Publication year - 2014
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/aas.12327
Subject(s) - medicine , confidence interval , calibration , receiver operating characteristic , intensive care unit , intensive care , norwegian , standardized mortality ratio , interval (graph theory) , saps ii , statistics , apache ii , intensive care medicine , mathematics , linguistics , philosophy , combinatorics
Background Mortality prediction is important in intensive care. The S implified A cute P hysiology S core ( SAPS ) II is a tool for predicting such mortality. However, the original SAPS II is poorly calibrated to current intensive care unit ( ICU ) populations because it draws on data, which is more than 20 years old. We aimed to improve the calibration of SAPS II using data from the N orwegian I ntensive C are R egistry ( NIR ). This is the first recalibration of SAPS II for Nordic data. Methods A first‐level customization was applied to improve calibration of the original SAPS II model (Model A ). NIR data used covered more than 90% of adult patients admitted to ICUs in N orway from 2008 to 2010 ( n = 30712). Results The modified SAPS II , Model B , outperformed the original Model A with respect to calibration. Model B gave more accurate predictions of mortality than Model A ( H osmer– L emeshow's C : 22.01 vs. 689.07; Brier score: 0.120 vs. 0.131; C ox's calibration regression: α = −0.093 vs. −0.747, β = 0.921 vs. 0.735, (α|β = 1) = −0.009 vs. −0.630). The standardized mortality ratio was 0.73 [95% confidence interval ( CI ) of 0.70–0.76] for Model A and 0.99 (95% CI of 0.95–1.04) for Model B . Discrimination was good for both models (area under receiver operating characteristic curve = 0.83 for both models). Conclusions As expected, Model B is better calibrated than Model A , and both models have similar uniformity of fit and equal discrimination. Introducing Model B into Norwegian ICUs may improve precision in decision‐making. Units will have a more realistic benchmark for the assessment of ICU performance. Mortality risk estimates from Model B are better than previous SAPS II estimates have been.