Clinical relevance of trace element measurement in patients on initiation of parenteral nutrition

Background and Aims Serum zinc, copper and selenium are measured in patients prior to commencing on parenteral nutrition; however, their interpretation can be difficult due to acute phase reactions. We assessed (i) the relationship of raised C-reactive protein with trace elements and albumin (ii) benefits of measuring trace elements when C-reactive protein is raised in patients requiring short-term parenteral nutrition. Methods Samples were collected for zinc, copper, selenium and albumin at baseline and then every two weeks and correlated with C-reactive protein results in patients on parenteral nutrition. Results were categorized into four groups based on the C-reactive protein concentrations: (i) <20mg/L, (ii) 20-39mg/L, (iii) 40-79mg/L and (iv) 80mg/L. Results In 166 patients, zinc, selenium and albumin correlated (Spearman's) negatively with C-reactive protein; r=-0.26, P<0.001 (95% CI -0.40 to -0.11), r=-0.44, P<0.001 (-0.56 to -0.29) and r=-0.22 P=0.005 (-0.36 to -0.07), respectively. Copper did not correlate with C-reactive protein (r=0.09, P=0.25 [-0.07 to 0.25]). Comparison of trace elements between the four groups showed no difference in zinc and copper (both P>0.05), whereas selenium and albumin were lower in the group with C-reactive protein>40mg/L (P<0.05). Conclusion In patients on short-term parenteral nutrition, measurement of C-reactive protein is essential when interpreting zinc and selenium but not copper results. Routine measurement of trace elements prior to commencing parenteral nutrition has to be considered on an individual basis in patients with inflammation.