Whole blood titanium metal ion measurement reproducibility of two laboratories

BACKGROUND: Metal ion blood concentrations evaluation can be useful in monitoring wear and corrosion of orthopedic implants. Elevated metal ion level may help detecting defective hip arthroplasty implants and serve as an indicator for revision surgery. Our objective was to evaluate the reproducibility of titanium metal ion level measurements by two different laboratories. METHODS: Seventy-one whole blood samples were collected from 64 patients with unilateral ceramic-on-ceramic hip arthroplasty. For each patient, two whole blood samples were collected and analyzed in two different laboratories. RESULTS: For each case, laboratory 1 had significantly higher values than laboratory 2. There was a clinically significant absolute difference between the two laboratories, above the predetermined threshold, for 90% of samples. A mean variation ratio of 410% between the two laboratories was found. CONCLUSION: Not all laboratories use the same techniques and calibrations to perform these measurements. Therefore, their results should be interpreted with caution and clinical decision should rely on metal ion trends provided by the same laboratory.