Increased sensitivity of patch testing by standardized tape stripping beforehand: a multicentre diagnostic accuracy study

BACKGROUND: As a modification of patch testing, the strip patch test was established to obtain more sensitive and reliable test results. Comparative data on diagnostic accuracy for both tests are missing. OBJECTIVES: To compare the diagnostic accuracy of strip patch tests and patch tests in detecting sensitizations in patients with suspected allergic contact dermatitis by using patient history as the reference standard. PATIENTS/METHODS: In a multicentre, prospective, investigator-blinded study 790 patients were enrolled. The defined reference standard was established prior to patch testing. Patch tests were performed with nickel sulfate, potassium dichromate, and lanolin alcohol. Duplicate tests were simultaneously performed on both sides of the back, of which one randomly chosen side was tape stripped beforehand, according to a standardized procedure. Primary outcome was the difference in sensitivity between strip patch test and patch test. RESULTS: Seven hundred and eighty-seven patients were included in the analysis. Strip patch tests detected considerably more sensitization to nickel sulfate and potassium dichromate than patch tests: differences of sensitivities were 16.4% (95% CI, 8.7-24.1%) for nickel sulfate and 25.0% (95% CI, 8.9-41.0%) for potassium dichromate, both favouring the strip patch test. CONCLUSIONS: The standardized strip patch test proved to be accurate and clinically safe and is promising to improve diagnosis of allergic contact dermatitis beyond the patch test.