CD32 Patient says nickel, patch says…? Measuring accuracy of self-reported nickel allergy: a single-centre audit

Abstract

Nickel is the most common contact allergen worldwide and a frequent reason for referral for patch testing, including patients reporting ‘metal allergy’ prior to joint replacement surgery. Self-reported nickel allergy is used in clinical decision making, but its diagnostic accuracy varies. The aim of this audit was to determine the prevalence of self-reported nickel allergy and nickel patch test positivity in patients attending for patch testing, and to evaluate the diagnostic performance of self-reporting against patch testing as the reference standard. We performed a retrospective audit of all patients who attended for patch testing at the University Hospitals of Leicester Contact Dermatitis Unit between February 2023 and May 2025. All patients were tested to the British baseline series, which includes nickel(Ii) sulfate hexa­hydrate 5.0% in petrolatum. On day 0, patients were asked if they ‘get a rash with metal objects or jewellery’. A ‘yes’ response was classified as self-reported nickel allergy. Demographics, atopy, anatomical site and concomitant patch test reactions were extracted, and descriptive analyses and χ2-tests were performed. The sensitivity and specificity of self-report were calculated in comparison with patch test results at day 4. In total 243 patients were included. Of these, 65 (26.7%) self-reported nickel allergy (59 female, 6 male; mean age 44 years). Overall, 49 (20.2%) had a positive nickel patch test, while 31 (12.8%) both self-reported and tested positive. Self-reporting demonstrated a sensitivity of 63.3% and specificity of 82.4%. There was a strong association between self-reporting and patch test positivity (P < 0.001). Among nickel-positive patients, 21% reacted to nickel alone, 33% to nickel plus other metals and 46% to nickel plus nonmetal allergens. The face (53%) and hands (49%) were the most commonly involved sites. Self-reported nickel allergy showed moderate sensitivity and good specificity for nickel patch test positivity, which is consistent with previous studies. Reliance on self-reporting alone risks both missed true allergy and unnecessary avoidance or referral.