Lymphocyte transformation testing for quantifying metal-implant-related hypersensitivity responses.

Hypersensitivity to metallic implants has been documented in case reports and cohort studies. However, this phenomenon remains unpredictable and poorly understood. There is continuing concern about the extrapolation of dermal patch testing to the periimplant environment. The utility of lymphocyte transformation testing (LTT) for predicting implant-related sensitivity in orthopedic patients was evaluated by contrasting LTT and patch-testing protocols and examining original cohort LTT data of subjects with and without implants. LTT of peripheral blood lymphocytes was performed, using four groups: (1) age-matched controls; (2) patients with osteoarthritis (preimplant), with and without dermal metal sensitivity; and (3) patients with total hip arthroplasty. A stimulation index of greater than 2 ( p < .05) indicated metal sensitivity. Patients with osteoarthritis and a history of metal sensitivity were more reactive to nickel than were those of any other group, as expected (ie, 66% incidence and average stimulation index of > 20). However, subjects with implants (group 3) were threefold more reactive to chromium (p < .04) than were controls (group 1) or subjects with osteoarthritis (group 2). Quantifiable lymphocyte reactivity as exemplified by increased incidence and average reactivity levels was metal implant specific (characteristic of adaptive immune responses) and suggests that LTT may be useful in the determination of implant-specific sensitivity. Advantages of LTT include quantitative results and the facilitation of multichallenge agent and dose testing. Thus, LTT (provided by laboratories fully disclosing testing methods) may be an additional tool in the armamentarium of physicians.