Methods

Subject Groups: Blinded de-identified data from patients with TJR referred for metal hypersensitivity testing using a lymphocyte transformation test (LTT) and serum markers of inflammation using Luminex Multi-Analyte Assay was approved by Rush University IRB and retrospectively reviewed. None of the patients had radiographically identifiable osteolysis. Two groups of TJA patients were tested: Group 1: Well-functioning implant (<3 yrs. post-op), with no self-reported pain, i.e. <1 on 0–10 VAS scale (n=8) and Group 2: Painful TJR (<3 yrs. post-op), with self-determined pain of >8 on a 0–10 VAS scale at the time of blood draw (n=25). Metal-LTT: Peripheral blood mononuclear cells (PBMCs) were collected from 30mL of peripheral blood by Ficoll gradient separation. PBMCs were cultured with NiCl2. 3H Thymidine was added at day 5 of culture and 3H thymidine incorporation was analyzed using a beta scintillation counter at day 6. A stimulation index (SI) of reactivity was calculated by dividing scintillation counts per minute (cpms) of Ni challenged cells by those of untreated controls. A SI of <2 was considered nonreactive, 2 to <4 was mildly reactive and 4 to <8 was reactive. Luminex Assay: Serum samples were collected from whole blood and were analyzed according to manufacturer's protocols. Statistical analysis: Statistical differences were determined using unpaired t-test with Welch's correction with statistical significance at p≤0.1 (90% confidence interval).