High Histamine Control Concentration Leads to False Negative Allergy Skin Testing

Area of Science:

• Allergy and Immunology
• Diagnostic Accuracy
• Dermatological Testing

Background:

• Reliability of allergy skin tests is influenced by reagent and control selection.
• Histamine concentrations of 1 mg/mL and 6 mg/mL are used, but the rationale for choice and its impact on diagnosis are understudied.

Purpose of the Study:

• To compare false negative rates of allergen skin tests between UniTest PC (1 mg/mL histamine) and Quintip devices (6 mg/mL histamine).
• To evaluate diagnostic accuracy for four common aeroallergens using different histamine concentrations.

Main Methods:

• Subjects (18-65 years) with cat/ragweed allergy symptoms underwent skin prick testing with four aeroallergens and histamine controls.
• Nasal allergen challenge (NAC) was performed on individuals with discordant skin test results between devices.
• Primary outcomes included false negative rates and sensitivity of skin test devices.

Main Results:

• Significant differences in wheal size were observed between devices for all tested allergens (p < 0.0053).
• Overall allergen sensitivity was 97% for UniTest (1 mg/mL histamine) versus 78% for Quintip (6 mg/mL histamine).
• Most false negatives were associated with the 6 mg/mL histamine concentration.

Conclusions:

• The 6 mg/mL histamine concentration may contribute to misinterpreting aeroallergen skin prick test results.
• Lower histamine concentrations (1 mg/mL) may improve the sensitivity of allergy skin testing.