Does nickel allergy play a role in the development of in-stent restenosis?

OBJECTIVES It was suggested that coronary in-stent restenosis might be triggered by allergy to nickel and molybdenum ions released from stainless-steel stents. We sought to explore any possible relationship between nickel allergy and in-stent restenosis. MATERIALS AND METHODS 50 patients were studied, who underwent elective follow-up coronary angiography for recurrent symptoms after prior coronary stenting, at least 3 months following the index procedure. Consecutively, we enrolled 25 patients with > or = 50% in-stent restenosis (study group), and 25 others with < 50% restenosis (control group), as revealed by coronary angiography. Evaluation for nickel allergy was performed using 5% nickel sulphate solution in petroleum applied as a patch test to the interscapular region by the Finn chamber method. A positive test was defined as an inflammatory response with erythema, edema, papulovesicles, or infiltration after 48 or 72 hours. RESULTS The mean age of the whole study cohort was 55.9 +/- 13.9 years, 44 (88%) being males. Two patients of the study group (8%) had a history of contact allergy to metals. However, both of them showed a negative patch test result. No patient in the control group had a history of metal allergy (p > 0.05). Only one patient in the study group (4%) had a positive patch test result for nickel contact allergy, whereas all patients in the control group had a negative result (p > 0.05). CONCLUSIONS Based on the available evidence, a cause-effect relationship between nickel allergy and in-stent restenosis cannot be confirmed.