D2.56 - Regionally Adapted Patch Test Panels Improve Diagnostic Resolution by Revealing Hidden Polysensitization in Allergic Contact Dermatitis

Diagnosis of allergic contact dermatitis (ACD) depends on the ability of patch test to reflect region-specific exposure patterns. Globally standardized series may underestimate clinically relevant sensitizations and inadequately capture complex polysensitization profiles. The present study compared the diagnostic performance and sensitization of the Brazilian Standard Series with an expanded Latin American patch test series.

This study encompassed 142 consecutive patients, who were stratified based on the Standard Series (comprising 30 substances; n=74) and the Latin American Series (comprising 40 substances; n=68). Groups were comparable regarding sex, age, and baseline nickel sensitization. Outcomes included overall positivity, number of positive allergens per patient (polysensitization), and metal co-sensitization assessed by odds ratios (OR).

The global positivity rate for more than one allergen was 85.3% in the Latin American Series and 75.7% in the Standard Series, with no significant difference (p = 0.150). However, the Latin American Series was superior to the Standard Series in detecting polysensitization, with a higher mean number of allergens identified per patient (2.45 vs 2.12; p = 0.002). The increase was driven by sodium tetrachloropalladate (38.2%) and thimerosal (19.1%).  Co-sensitization analysis showed a strong association between nickel sulfate and sodium tetrachloropalladate (OR = 16.6; p<0.001), consistent with structural cross-reactivity, while revealing additional palladium sensitization not detected by nickel testing alone. In contrast, cobalt chloride sensitization occurred independently of nickel sensitization (OR = 1.01; p = 0.980).

Despite similar initial screening positivity, the regionally adapted Latin American Series provided superior diagnostic resolution by uncovering hidden polysensitization and clinically relevant sensitizations missed by the standard panel. These findings support panel customization as a strategy to improve diagnostic precision and optimize clinical management in ACD.