Case mix, outcome and length of stay for admissions to adult, general critical care units in England, Wales and Northern Ireland: the Intensive Care National Audit & Research Centre Case Mix Programme Database

Abstract

Introduction: The present paper describes the methods of data collection and validation employed in the Intensive Care National Audit & Research Centre Case Mix Programme (CMP), a national comparative audit of outcome for adult, critical care admissions. The paper also describes the case mix, outcome and activity of the admissions in the Case Mix Programme Database (CMPD).

Methods: The CMP collects data on consecutive admissions to adult, general critical care units in England, Wales and Northern Ireland. Explicit steps are taken to ensure the accuracy of the data, including use of a dataset specification, of initial and refresher training courses, and of local and central validation of submitted data for incomplete, illogical and inconsistent values. Criteria for evaluating clinical databases developed by the Directory of Clinical Databases were applied to the CMPD. The case mix, outcome and activity for all admissions were briefly summarised.

Results: The mean quality level achieved by the CMPD for the 10 Directory of Clinical Databases criteria was 3.4 (on a scale of 1 = worst to 4 = best). The CMPD contained validated data on 129,647 admissions to 128 units. The median age was 63 years, and 59% were male. The mean Acute Physiology and Chronic Health Evaluation II score was 16.5. Mortality was 20.3% in the CMP unit and was 30.8% at ultimate discharge from hospital. Nonsurvivors stayed longer in intensive care than did survivors (median 2.0 days versus 1.7 days in the CMP unit) but had a shorter total hospital length of stay (9 days versus 16 days). Results for the CMPD were comparable with results from other published reports of UK critical care admissions.

Conclusions: The CMP uses rigorous methods to ensure data are complete, valid and reliable. The CMP scores well against published criteria for high-quality clinical databases.

Figure 1

Directory of Clinical Databases' criteria for assessing the coverage and accuracy of a clinical database (adapted from [3,4]).

Figure 2

An example of the Intensive Care National Audit & Research Centre Coding Method – bacterial pneumonia.

Figure 3

Data collection timeline for the Case Mix Programme (CMP). Data are also collected where appropriate at original critical care unit admission (date) and at ultimate critical care unit discharge (date, survival status), which may be before or after admission to/discharge from the hospital housing the CMP unit. APACHE, Acute Physiology and Chronic Health Evaluation; ICU, intensive care unit; MPM, Mortality Probability Model; SAPS, Simplified Acute Physiology Score.

Figure 4

Performance of the Case Mix Programme Database (CMPD) against Directory of Clinical Databases (DoCDat) criteria. CMPD ratings compared with the median (interquartile [IQR] range) from all 154 databases in DoCDat.

Figure 5

Top 10 primary reasons for admission in the Case Mix Programme Database. Expressed as a percentage of the total number of admissions with a primary reason for admission specified (N = 129,452). The numbers within each bar are the numbers of admissions.