Characteristics and Outcomes of Patients With Negative Patch Test Results and Systematic Literature Review.

BACKGROUND

Patients with negative patch test (NPT) results do not receive allergy avoidance counselling, and their experiences are important to understand.

OBJECTIVE

To describe the clinical presentation and outcomes associated with NPT results.

METHODS

Cross-sectional study analysing data from an IRB-approved REDCap registry. A systematic review was performed searching Ovid MEDLINE, Embase and Cochrane Library Databases.

RESULTS

161/1001 patients (769 female, 230 male) 16.1%, had NPTs. Mean age was 52.2 years (standard deviation 20.6). Median age, female predominance, race/ethnicity, duration of rash and number of patches placed was not significantly different between negative and positive patch test results. More NPT patients had leg involvement (p = 0.04) and prior biopsy (p = 0.002). 29.9% had a non-dermatitis diagnosis. The investigator and patient assessments were significantly improved post-patch testing. In a systematic review of 34 studies, 77261 patients, the NPT rate ranged between 16.7% and 83.1% and number of patches placed from 20 to 102. The most common areas of dermatitis were the hands.

CONCLUSIONS

In our cohort and systematic review, a minority of patients have NPTs, with no major demographic differences. NPT patients have had prior biopsies, suggesting an unusual presentation. They were also commonly diagnosed with other forms of dermatitis, although 30% had a non-dermatitis diagnosis.