Establishment of a candidate reference method and verification of reference intervals for serum copper in pregnant and non-pregnant women

Abstract

Background

Serum copper is an essential trace element, and accurate quantification is important for assessing copper status in pregnancy and supporting early clinical interventions. However, current serum copper assays face several challenges, including potential inaccuracy, poor comparability between methods, and difficulties in transferring reference intervals (RIs) between populations. This study aimed to establish a simple inductively coupled plasma mass spectrometry (ICP-MS)-based candidate reference method for serum copper to strengthen the reference measurement system, and to verify whether recently proposed multicenter RIs for serum copper can be transferred to a Chinese population.

Methods

Cobalt was used as the internal standard. After digestion with Optima-grade ultrapure nitric acid, samples were diluted 100-fold with ultrapure water. The ⁶³Cu/⁵⁹Co ratio was measured in helium collision mode, with the gas flow rate set to 5 mL/min. Analytical performance was validated, and serum copper RIs in pregnant and non-pregnant women were subsequently verified.

Results

A candidate reference method was established. The method demonstrated excellent linearity, with a correlation coefficient (R) exceeding 0.99998 over the range 0–13.75 μg/g. The total precision ranged from 0.30% to 0.40%. The spike recovery was 100.06% (99.95–100.14%). Trueness was confirmed by measurements of NIST SRM 1598a, which fell within the certified value and its stated uncertainty. The RI for healthy non-pregnant women was transferable to healthy Chinese women, whereas the pregnancy-specific RI for serum copper was not fully transferable and requires further adjustment for Chinese women.

Conclusion

A highly sensitive and specific candidate reference method for serum copper was established, strengthening the reference measurement system and contributing to the standardization and harmonization of serum copper assays. Pregnancy-specific RIs for serum copper in Chinese women should be established.