Skin testing in allergy

Systemic reactions associated with subcutaneous allergen immunotherapy: timing and risk assessment

BACKGROUND

Subcutaneous allergen immunotherapy (SCIT) is associated with risk of systemic reaction. Although risk factors have been identified, the incidence of immunotherapy-related systemic reactions has not changed in recent years.

OBJECTIVES

To examine patterns of systemic reaction and determine whether risk of systemic reaction from SCIT is associated with patterns of response to skin tests to inhalant allergens recorded before receiving SCIT.

METHODS

We carried out a retrospective review from January 2001 to December 2007. Patterns of systemic reaction from immunotherapy were examined. Cases were matched with controls by age (±10 years), sex, and time of injection (±1 week) to determine whether a pattern of more than 33% 3+ and 4+ skin test responses is associated with elevated risk for systemic reaction.

RESULTS

Rate of systemic reaction from SCIT was 0.28% (46/16,375) per injection visit. Twenty patients had 46 systemic reactions. All severe reactions occurred within 30 minutes. The estimated odds of systemic reaction were almost 6 times higher for patients with more than 33% 3 to 4+ positive skin tests (OR = 5.83; 95%CI: 1.23-27.59, P = .026). For each additional 4+ skin test, the estimated odds for systemic reaction increased by 17% (P = .020).

CONCLUSIONS

A small number of patients receiving SCIT account for a large proportion of systemic reactions. Skin test patterns demonstrating a greater number of larger skin tests responses to inhalant skin testing are associated with significantly elevated risk for systemic reaction in patients receiving SCIT.

Objective evaluation of skin prick test reactions using digital photography

BACKGROUND

The skin prick test has been used worldwide to determine IgE-mediated hypersensitivity. However, the most current method to record this reaction has problems with accuracy and precision.

OBJECTIVE

To demonstrate a new approach to measure the skin prick reaction and its kinetics with precision.

METHODS

The skin prick test was induced using histamine or Dermatophagoides pteronyssinus antigen in 80 volunteers aged 4 and 67 years who had different skin colors. Digital photographs were obtained at 0, 3, 5, 10, 15 and 20 min. The mean wheal and erythema area as well as the erythema intensity were determined using Adobe Photoshop software. The accuracy and precision of this approach were also evaluated.

RESULTS

The digital photographic analysis measured the wheal and erythema sizes independent of the antigen or skin color with precision. In addition, a new variable of this test, the skin erythema intensity, could be determined objectively using the chromaticity of reflected light.

CONCLUSIONS

Digital photographic analysis is a precise and objective method to evaluate the skin prick test reaction, which can be used independent of the patient's skin color in clinical or research settings.