Assessing the validity of self-reported history of rash caused by metal or jewellery

The use of metal-containing bio-devices is becoming increasingly common. Self-reported history of dermatitis with metal exposure is not established as being predictive for metal allergy.

To assess the validity of two screening questions addressing metal allergy.

At Massachusetts General Hospital Contact Dermatitis Clinic, 2132 consecutive patients were asked either 'Do you get rashes when jewellery touches your skin' (Q1; N = 1816) or 'Do you get rashes when metal touches your skin?' (Q2; N = 316) before being patch tested.

Testing showed that 20% of subjects had positive reactions to nickel, 7.4% had positive reactions to cobalt, and 5.8% had positive reactions to chromium. Q1 was 40% sensitive (95%CI: 35-45%). The positive predictive value (PPV) was 51%, and the negative predictive value (NPV) was 82%. Q2 was 77% sensitive (95%CI: 68-84%). The PPV was 71%, and the NPV was 84%. Q2 was 37% more sensitive than Q1 (p < 0.0001), with a higher relative risk (RR) (4.75, p < 0.001) than Q1 (RR = 3.01, p < 0.001).

Patient-reported metal allergy, although not perfect, is a reasonable method for metal allergy screening to help identify those needing further objective evaluation by patch testing.