Title : Overcoming false negative patch tests: A systematic approach
Abstract:
Background: Exogenous allergens can cause allergic contact dermatitis (ACD). To help identify and discern which allergen is causing ACD, clinicians use patch tests. Looking into potential reasonings for false negatives is particularly helpful when a patient’s history suggests a potential negative result and the patch test is also negative. Potential solutions include using different vehicles, concentration, increasing reading time, repeat open application testing and repeating the patch test. If a false-negative patch test is suspected, then intradermal testing can also be administered to ensure the specificity of the patch test result.
Objective: A systematic review was conducted to compile various reasonings and solutions for false- negative patch tests in suspected ACD patients.
Methods: A systematic review was done utilizing EMBASE, Scopus, PubMed, and Google Scholars and 49 articles were included. Search terms included “False negative patch test, False-negative patch test, allergic contact dermatitis and ACD.”
Results: Factors that led to false-negative patch test results include immunosuppressive therapy, UV exposure, and allergen concentration. Furthermore, potential solutions include using different vehicles, concentration, increasing reading time, repeat open application testing and repeating the patch test.
Conclusions and Impact: Because patch testing is considered a gold standard diagnostic tool for ACD, it is important to minimize false-negative results, especially when a patient’s history and physical exam provide strong proof for ACD. By mitigating false negative patch test results, clinicians can accurately pinpoint which allergen is causing ACD and accordingly formulate appropriate treatment plans for patients. Here, we found immunosuppressive therapy, UV exposure, and allergen concentration as contributing factors to false-negative patch tests. Furthermore, using different vehicles, minimizing technique errors, increasing reading time, repeat open application testing and repeating the patch test are solutions to overcome and prevent false-negative patch tests. Future studies should incorporate surveys indicating a clinician’s confidence in ACD diagnosis from a patient’s history and physical exam if a false-negative result is obtained. Additionally, further studies can examine the potential reasonings and solutions to false negative tests in the pediatric population and compare them to the adult population.
