Establishment and verification of chromium and cobalt concentrations in joint fluids from a reference population

This study aims to establish joint fluid reference levels for Chromium (Cr) and Cobalt (Co) in a reference population of available fluid types. Method performance was evaluated on an existing urine matrix calibration method using inductively coupled plasma-mass spectrometry. Method performance characteristics, including intra- and inter-assay imprecision, accuracy, linearity, AMR (analytical measurement range), sensitivity, and carryover were determined in accordance with clinical laboratory standards. Additionally, analytical and clinical recoveries were assessed to investigate comparability between available joint fluid types and existing calibrators prepared in urine to demonstrate acceptability of a matrix-substitution design. 124 de-identified joint fluid samples submitted for unrelated testing were used to establish the reference levels. Reference levels were determined, by using the 97.5th percentile, to be <20.4 µg/L for Cr and <29.9 µg/L for Co. In addition, the presented method overcomes the lack of an ample volume of joint fluid to use for matrix matched calibrators by employing a urine-based calibration curve. The data demonstrate acceptable matrix comparability.