When to test for cat scratch disease (CSD) or cat allergy?

From the Guidelines

Testing for cat scratch disease (CSD) or cat allergy is recommended when a patient presents with symptoms such as a papule or pustule at the site of a cat scratch or bite, followed by lymphadenopathy, which typically develops within 3 weeks after inoculation 1. When to test for CSD or cat allergy depends on various factors, including the patient's symptoms, medical history, and exposure to cats.

• Testing for CSD is crucial when a patient presents with symptoms such as a papule or pustule at the site of a cat scratch or bite, followed by lymphadenopathy, which typically develops within 3 weeks after inoculation 1.
• For cat allergy, testing is recommended when a patient experiences symptoms of allergic rhinitis, such as sneezing, runny nose, and itchy eyes, after exposure to cats 1.
• The diagnosis of CSD can be difficult, but serological testing, PCR, and a positive Warthin-Starry silver stain of infected lymph node tissue can support the diagnosis 1.
• For cat allergy, skin testing and in vitro IgE antibody tests can be used to determine the presence of specific IgE antibodies 1.
• Avoidance is the most effective way to manage animal sensitivity, and patients should be advised to consider removing the cat or taking measures to reduce exposure, such as confining the cat to an uncarpeted room or using a HEPA air purifier 1.

From the Research

Diagnosis of Cat Allergy

• The diagnosis of cat allergy is based on a medical history and physical examination that are consistent with each other and is confirmed with positive results on specific IgE skin tests 2.
• The skin prick test (SPT) is the most preferred method to demonstrate sensitization to allergens, and a cut-off value of 5.5 mm may indicate cat allergy 3.
• Molecular diagnosis is strongly recommended, especially in polysensitized patients 2.

Testing for Cat Scratch Disease (CSD)

• There is no direct evidence in the provided studies to assist in answering when to test for CSD.
• However, it is essential to note that CSD is a different condition from cat allergy, and testing for CSD would require a separate approach.

When to Test for Cat Allergy

• Testing for cat allergy is recommended when symptoms are present, such as respiratory symptoms, and a medical history and physical examination suggest an allergy to cats 2, 3.
• The prevalence of sensitization to cats varies by country, exposure time, and predisposition to atopy, and it is estimated that 26% of European adults are sensitized to cats 2.
• Children with cat allergies have mostly reported respiratory symptoms, and the incidence of cat allergies in children has increased over the years 3.