Healthcare processes of laboratory tests for the prediction of mortality in the intensive care unit: a retrospective study based on electronic healthcare records in the USA

OBJECTIVES: Healthcare process carries important prognostic information for patients, but the healthcare processes of laboratory tests have not yet been investigated for patients in the intensive care unit (ICU). The study aimed to investigate the effect of healthcare processes of laboratory tests on hospital mortality, with the hypothesis that the addition of healthcare processes could improve the discrimination for mortality outcome. DESIGN: The study included 12 laboratory tests. There were two dimensions for each laboratory test. One was the pathophysiology value; and the other was the healthcare process variables including the clock hour, the number of measurements and the measurement time from ICU admission. Generalised additive model was employed to investigate the effect of continuous variables on mortality. Generalised linear models with and without healthcare process variables were compared for their discrimination power. SETTING: ICUs in an US-based hospital. PARTICIPANTS: Adult patients included in the critical care big data Medical Information Mart for Intensive Care. PRIMARY AND SECONDARY OUTCOME MEASURES: The hospital mortality was the primary outcome. RESULTS: A total of 52 963 adult patients with complete ICU stay information were included for analysis. The mortality rate was 12.3%. Lower number of tests such as 1–3 times were associated with the lowest mortality for most laboratory tests. However, the hematocrit, glucose and potassium required 6–10 measurements for the first 24 hours to reach the lowest mortality rate. In n of the 12 prediction models involving laboratory tests, the addition of healthcare process variables was associated with significantly increased area under receiver operating characteristics. CONCLUSIONS: The study showed that healthcare processes of laboratory tests were independently associated with hospital mortality. The addition of healthcare processes to the pathophysiology value could increase the discrimination for mortality outcome.