The Interchangeability of Plasma and Whole Blood Metal Ion Measurement in the Monitoring of Metal on Metal Hips

Abstract

One hundred and twenty six paired samples of plasma and whole blood were measured with inductively coupled plasma mass spectrometry technique for metal ions analysis to determine a relationship between them. There was a significant difference between the mean plasma and whole blood concentrations of both cobalt (Co) and chromium (Cr) (p < 0.0001 for both Co and Cr). The mean ratio between plasma and whole blood Cr and Co was 1.56 (range: 0.39–3.85) and 1.54 (range: 0.64–18.26), respectively, but Bland and Altman analysis illustrated that this relationship was not universal throughout the range of concentrations. There was higher variability at high concentrations for both ions. We conclude that both these concentrations should not be used interchangeably and conversion factors are unreliable due to concentration dependent variability.

Comparison of metal ion concentrations and implant survival after total hip arthroplasty with metal-on-metal versus metal-on-polyethylene articulations

“…The Medicines and Healthcare products Regulatory Agency (MHRA) recommended in 2010 the use of whole blood to measure Co and Cr levels (Malek et al. 2015b ). When we initiated the study in 1998, we chose to analyze serum metal ions, which was recommended at the time.…”

Is the synovial fluid cobalt-to-chromium ratio related to the serum partitioning of metal debris following metal-on-metal hip arthroplasty?

“…Several in vivo and in vitro studies have previously investigated the relationship between the concentrations of Cr and Co in serum, WB, and erythrocytes. In general, the results have been consistent: 1) serum and WB samples, while closely correlated, cannot be used interchangeably due to unexplained variation; 13,14 2) serum concentrations of Cr tend to be higher than WB samples, indicating Cr is released from MoM hips mostly in the trivalent (Cr 3+ ) form; 11,15-17 and 3) serum partitioning of Co is less well understood, with conflicting evidence. 10,15 However, variations in serum and WB concentrations of Co are, in general, smaller than those observed with Cr samples.…”

Correlation between Serum Metal Ion Levels and Adverse Local Tissue Reactions after Conserve® plus Hip Resurfacing Arthroplasty

“…From the senior author's database of 1,375 MoM HRA, 387 patients were identified, in whom 1,071 serum metal ion studies had been performed. Whole blood ion studies were excluded because serum and whole blood levels are not interchangeable and conversion factors are concentration-dependent (19). From this cohort, we selected all the patients who had at least 1 study performed 1 year or longer after surgery and were treated with a Conserve® Plus hip resurfacing system (Microport Inc.) on one side, all other joints being free of any arthroplasty.…”