[Completeness of ICU activity reports sent to French healthcare authorities]

[ICU performance: results of a French study involving 80,000 ICU stays]

OBJECTIVE

The Standard Mortality Ratio (SMR), comparing the observed in-hospital mortality to the predicted, may measure the intensive care units (ICU) performance.

STUDY DESIGN

Multicentric retrospective national study.

METHODS

A probability model using a severity score such SAPS II calculated the predicted mortality rate. A national French study has been undertaken to compare the SMR of ICUs and looked for explanation.

RESULTS

One hundred six units, 34 were medical (32%), 18 surgical (17%) and 57 medical/surgical (51%) participated to the study. Forty-six ICUs (43%) were located in teaching hospitals. The SMR of the 87,099 stays was 0.84 (0.82-0.85). The SMR of ICUs varied from 0.41 to 1.55. Ten units had a SMR>0.85, which suggested a low performance. They had more stays for cardiovascular failures, as compared with others. The best units (SMR<0.82) had more stays for drug overdose. The SMR increased with the number of organ failures, from 0.47 with zero failure to 1.11 with 4 or more organ failures. The stays with cardiovascular failure, either unique or associated, had a higher SMR. The 7935 stays with a drug overdose had a SMR of 0.12 (0.10-0.14), which suggested a bad calibration of the model in theses cases.

CONCLUSION

The case mix must be taken in account when comparing the ICUs performance by the mean of SMR, particularly when the units admitted a lot of drug overdoses.

Mortality prediction using SAPS II: an update for French intensive care units

INTRODUCTION

The standardized mortality ratio (SMR) is commonly used for benchmarking intensive care units (ICUs). Available mortality prediction models are outdated and must be adapted to current populations of interest. The objective of this study was to improve the Simplified Acute Physiology Score (SAPS) II for mortality prediction in ICUs, thereby improving SMR estimates.

METHOD

A retrospective data base study was conducted in patients hospitalized in 106 French ICUs between 1 January 1998 and 31 December 1999. A total of 77,490 evaluable admissions were split into a training set and a validation set. Calibration and discrimination were determined for the original SAPS II, a customized SAPS II and an expanded SAPS II developed in the training set by adding six admission variables: age, sex, length of pre-ICU hospital stay, patient location before ICU, clinical category and whether drug overdose was present. The training set was used for internal validation and the validation set for external validation.

RESULTS

With the original SAPS II calibration was poor, with marked underestimation of observed mortality, whereas discrimination was good (area under the receiver operating characteristic curve 0.858). Customization improved calibration but had poor uniformity of fit; discrimination was unchanged. The expanded SAPS II exhibited good calibration, good uniformity of fit and better discrimination (area under the receiver operating characteristic curve 0.879). The SMR in the validation set was 1.007 (confidence interval 0.985-1.028). Some ICUs had better and others worse performance with the expanded SAPS II than with the customized SAPS II.

CONCLUSION

The original SAPS II model did not perform sufficiently well to be useful for benchmarking in France. Customization improved the statistical qualities of the model but gave poor uniformity of fit. Adding simple variables to create an expanded SAPS II model led to better calibration, discrimination and uniformity of fit, producing a tool suitable for benchmarking.