Serum chromium levels sampled with steel needle versus plastic IV cannula. Does method matter?

PURPOSE Modern metal-on-metal (MoM) joint articulations releases metal ions to the body. Research tries to establish how much this elevates metal ion levels and whether it causes adverse effects. The steel needle that samples the blood may introduce additional chromium to the sample thereby causing bias. This study aimed to test that theory. METHODS We compared serum chromium values for two sampling methods, steel needle and IV plastic cannula, as well as sampling sequence in 16 healthy volunteers. RESULTS We found statistically significant chromium contamination from the steel needle with mean differences between the two methods of 0.073 ng/mL, for the first sample, and 0.033 ng/mL for the second. No difference was found between the first and second plastic sample. The first steel needle sample contained an average of 0.047 ng/mL more than the second. This difference was only borderline significant. CONCLUSION The chromium contamination from the steel needle is low, and sampling method matters little in MoM populations. If using steel needles we suggest discarding the first sample.