Intradermal skin testing (IDST) and
allergen-specific
IgE determination are used to determine
allergen sensitization. In cats, studies have found poor correlation between the two tests. However, these studies were mainly conducted in pet cats sensitized to unknown
allergens with unknown dose and duration of exposure. We hypothesized that in an experimental model of allergic sensitization where these variables are controlled, IDST would demonstrate greater sensitivity and specificity than would serum
allergen-specific
IgE determination. A model of feline
asthma employing Bermuda grass
allergen (BGA) or house dust mite
allergen (
HDMA) was used to test the hypothesis. Thirteen cats were assigned to undergo sensitization to BGA,
HDMA or saline (placebo). Bronchoalveolar lavage fluid confirmed development of an asthmatic phenotype. Serum collection and IDST were performed on D0, D28 and D50. A portion of serum was pooled, and an aliquot heat inactivated (HI) to destroy
IgE. Individual, pooled, and pooled HI samples were used for
allergen-specific
IgE determination using an Fc epsilon R1 alpha-based ELISA; pooled samples were also analyzed using an enzymoimmunometric assay. Sensitivity (SE), specificity (SP), and positive and negative predictive values (PPV and NPV) were calculated for IDST and for BGA- and
HDMA-specific
IgE. Combined results for IDST found SE=90.9%, SP=86.7%, PPV=83.3%, and NPV=92.9%. For ELISA-based serum
IgE testing, the SE=22.7%, SP=100%, PPV=100% and NPV=63.8%. The enzymoimmunometric assay did not detect sensitizing
IgE, but did detect
IgE reactivity to a variety of irrelevant
allergens (even in HI samples). Sensitivity of IDST was greater than sensitivity of serum
IgE measurement supporting use as a screening test for aeroallergens. Both IDST and
allergen-specific
IgE determination via ELISA were specific; either test can be used to guide selection of
allergens for
immunotherapy. The enzymoimmunometric assay was unreliable and cannot be recommended.