Poster Topical Area: Vitamins and Minerals

Location: Hall D

Poster Board Number: 491

P26-030 - Added value of plasma zinc as a mortality risk biomarker in the critically ill

Sunday, Jun 10
8:00 AM – 6:00 PM

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



Funding Source: Only funding received was for plasma zinc determinations in the match control group of patients. The funding came from the Department of Intensive Care at the Lyell McEwin hospital, Haydown Road, Elizabeth Vale South Australia 5112.
Figure 1. Graphic display of predicted survival curves from the Cox model, with 95% CI, for various covariate combinations over all patients.

Figure 2. The added value of zinc as assessed by the area under time dependent ROC curves. Superiority of the model including plasma zinc levels up to 100 days follow up.

CoAuthors: John Moran – The Queen Elizabeth Hospital, Adelaide, South Australia; Mrudula Kanhere – Lyell McEwin Hospital, Adelaide, South Australia; Peter Zalewski – Basil Hetzel Institute, University of Adelaide, South Australia; Garry Nind – Lyell McEwin Hospital, Adelaide, South Australia ; John Santamaria – St Vincents Hospital, Melbourne, Victoria, Australia

Sydney Jacobs

Consultant ICU and Consultant
Queen Elizabeth Hospital and Lyell McEwin Hospital
Adelaide, South Australia, Australia