Poster Topical Area: Vitamins and Minerals
Location: Hall D
Poster Board Number: 491
Objective: To assess the added value of plasma zinc level as a mortality risk biomarker in the critically ill.
Design: Over a 4-year period, in 2 ICUs, 2 patient cohorts were recruited; one with severe chronic liver disease (CLD) and the other without CLD (non-CLD), sex, age and weight matched. Predictors of overall 6-month outcome (as hazard ratios (HR)) were 3 determined by Cox regression (Figure 1). The added value of plasma zinc (normal range: 9-21 µmol/L) was estimated via time-dependent receiver operating characteristic (ROC) curves (Figure 2), and risk-reclassification measures: (continuous) net reclassification index (NRI>0) and integrated discrimination improvement (IDI) for survival data.
Results: The data-set comprised 142 patients, of mean (SD) age 54(12.3) years, APACHE III score 80.2(34.0) and SOFA score 6.5(4); 63% were male and overall 6-month mortality was 35.2 % (53.6 % in the CLD and 17.8 % in the non-CLF cohort). Plasma zinc was 5.3(2.2) µmol/L in the CLD cohort (n=69) and 8.1(2.9) µmol/L in the non-CLD cohort (n=73). Three predictors of 6-month outcome were SOFA score (HR1.30, 95% CI: 1.20, 1.41), ICU-site (HR0.51: 0.38, 0.90) and plasma zinc (0.78: 0.74, 0.94); Cox-model R2 was 0.57, 95%CI: 0.45, 0.70. Time-dependent ROC curves showed superiority of the model including plasma zinc, up to 100 days of follow-up. Similarly, the addition of plasma zinc produced significant risk reclassification over time: NRI>0: 0.692 (0.006, 0.982), P=0.013 and IDI: 0.066(0.009, 0.150), P=0.013; and median improvement in risk score: 0.041 (0.006, 0.131), P=0.020.
Conclusions: Plasma zinc levels were independently associated with mortality and demonstrated added-value as an over-time risk biomarker.
Key Words: plasma zinc, mortality, risk biomarker, critical illness
Consultant ICU and Consultant
Queen Elizabeth Hospital and Lyell McEwin Hospital
Adelaide, South Australia, Australia