B-165 Establishment of a Labile Bound Copper and Labile Bound Copper Ratio Reference Interval in a Healthy Adult Population

Abstract

Abstract Background While clinical tests are available to aid in the diagnosis of Wilson’s Disease (WD), some such as total copper determination lack sensitivity and specificity, while others such as liver tissue copper assessment are costly and invasive. WD affects copper metabolism and is known to cause low serum copper concentrations. In addition, an elevated percentage of total serum copper exists as non-protein bound or labile bound copper (LBC). Previous studies have shown that measuring the ratio of labile bound copper to total serum copper may aid in the diagnosis of WD. To support the utility of a laboratory developed test using serum LBC ratios to aid in the diagnosis of WD, serum samples from healthy donors were used to establish a reference range for LBC and the ratio of LBC to total copper in adults. Methods Serum samples were collected in trace metal free tubes from 214 donors (n = 110 male, n = 104 female) between the ages of 19–80 years old, selected against pre-determined exclusion criteria including acute hepatitis, chronic hepatitis, renal failure, biliary cirrhosis, celiac disease, and leukemia. Prior to analysis, samples went through a centrifugation-based preparation process to isolate the LBC fraction using molecular weight size exclusion filters and EDTA chelation. Samples were then analyzed via ICP-MS in kinetic energy discrimination (KED) mode to directly measure the LBC and total copper concentrations. LBC ratio values were determined from the LBC/total copper concentrations. Results Preliminary reference ranges were developed for both LBC and the LBC ratio based on the 2.5th and 97.5th percentiles with 95% confidence intervals. Established sex specific reference intervals for total copper were deemed acceptable per CLSI guidelines in document EP28-A3c, with ≤10% of results from this sample set falling outside of the established intervals. No statistically significant relationship was found in the mid-95th percentile between LBC concentration or ratio with age or sex. The reference intervals for LBC concentration were calculated as 13.41–104.66 and 11.69–106.50 ng/mL for females and males respectively. The reference intervals for LBC ratio were calculated as 1.04–8.12 and 1.17–10.48 for females and males respectively. Conclusions A reference range of LBC and LBC ratio has now been determined for the healthy adult population. Further testing can now be done on disease state populations to determine the sensitivity and specificity of LBC ratio in the detection, monitoring, or diagnosis of WD.