Diagnosis of Allergic Contact Dermatitis With the New Zealand Baseline Series

The New Zealand Baseline Series (NZBS) was developed in 2021 to ensure local patch testing was relevant to the population of New Zealand (NZ). It consists of 30 Core allergens and 30 Extended allergens. The aim of this study was to assess performance of the NZBS in diagnosing allergic contact dermatitis (ACD).

A retrospective review was performed of patients patch tested between February 2022 and December 2023, at a public tertiary dermatology clinic and at a private dermatology clinic in Auckland, NZ. Patient demographics and the positivity rate of each allergen were recorded. Performance of the NZBS in diagnosing ACD was categorised as full detection (all relevant allergens identified), partial detection (some, but not all, relevant allergens identified) and no detection (no relevant allergens identified).

In total, 209 patients were included in data analysis; 94 from the public clinic and 115 from the private clinic. In total, 105 patients (50%) were diagnosed with ACD with at least one relevant reaction on patch testing. Of those diagnosed with ACD, testing against the NZBS (60 allergens) had a full detection rate of 66%, partial detection in 21% and no detection in 13%.

Patch testing with the NZBS has a good detection rate for diagnosing ACD. However, detection of all relevant allergens requires supplementation with additional series and patients' own products. Regular updates to the series are required to improve diagnostic value in the population. We suggest combining study results, literature review and expert consensus to identify emerging or missed allergens not currently captured by the NZBS.