Sex differences in crude mortality rates and predictive value of intensive care unit-based scores when applied to the cardiac intensive care unit

Abstract

Background: Limited data exists regarding sex differences in outcome and predictive accuracy of intensive care unit-based scoring systems when applied to cardiac intensive care unit patients.

Methods: We reviewed medical records of patients admitted to cardiac intensive care unit from 1 January 2011-31 December 2016. Sex differences in mortality rates and the performance of intensive care unit-based scoring systems in predicting in-hospital mortality were analyzed. Calibration was assessed by the Hosmer-Lemeshow test and locally weighted scatterplot smoothing curves. Discrimination was assessed using the c statistic and receiver-operating characteristic curve.

Results: Among 6963 patients, 2713 (39%) were women. Overall in-hospital and cardiac intensive care unit mortality rates were similar in women and men (9.1% vs 9.4%, p=0.67 and 5.9% vs 6%, p=0.88, respectively) and in age and major diagnosis subgroups. Of the scoring systems, Acute Physiology and Chronic Health Evaluation III and Sequential Organ Failure Assessment had poor calibration (Hosmer-Lemeshow p value <0.001), while Simplified Acute Physiology Score II performed better (Hosmer-Lemeshow p value 0.09), in both women and men. All scores had good discrimination (C statistics >0.8). In the subgroups of acute myocardial infarction and heart failure patients, all scores had good calibration (Hosmer-Lemeshow p>0.001) and discrimination (C statistic >0.8) while in diagnosis subgroups with highest mortality, the calibration varied among scores and by sex, and discrimination was poor.

Conclusions: No sex differences in mortality were seen in cardiac intensive care unit patients. The mortality predictive value of intensive care unit-based scores is limited in both sexes and variable among different subgroups of diagnoses.

Keywords: Sex differences; cardiac intensive care unit; mortality; prediction.

Figure 1.

Locally weighted scatterplot smoothing (LOESS) calibration curves for overall CICU patients: (a) women and (b) men. Blue line: Acute Physiology and Chronic Health Evaluation (APACHE); red line: Simplified Acute Physiology Score (SAPS); green line: Sequential Organ Failure Assessment (SOFA). Model calibration that has complete concordance between estimated and observed risk (dashed line).

Figure 2.

Locally weighted scatterplot smoothing (LOESS) calibration curves for patients with cardiogenic shock: (a) women and (b) men. Model calibration that has complete concordance between estimated and observed risk (dashed line). Blue line: Acute Physiology and Chronic Health Evaluation (APACHE); red line: Simplified Acute Physiology Score (SAPS); green line: Sequential Organ Failure Assessment (SOFA).