Intradermal Skin Testing in Allergic Rhinitis and Asthma with Negative Skin Prick Tests

Taking medical history, physical examination, and performing some in vivo and in vitro tests are necessary for the diagnosis of allergy. Skin prick test (SPT) is considered as the standard method and first-line approach for the detection of allergic sensitization. Although mainly SPT is used for the detection of allergic sensitization, intradermal skin test (IDST) may be necessary, especially in patients with a negative SPT result. IDST is quite safe; however, is nowadays seldom used for detection of inhalant allergy and its value remains controversial. We aimed to investigate whether IDST is useful and necessary in diagnosis of respiratory allergies or not. This study involved 4223 patients with allergic rhinitis (AR) and/or bronchial asthma (BA). SPT results were positive in 2419 patients (57%) and negative in 1804 (43%). IDST was applied to 344 patients with marked allergic symptoms and with negative SPT results. Out of 344 patients, 152 (44%) showed allergic sensitization to IDST. The most commonly encountered allergic response was against the house dust mite (HDM) (32.6%). Allergic response against fungal spores was also relatively high (22%), while the pollen allergy rate (4.3%) was quite low. In BA patients with negative prick test, IDST made a significant contribution to the diagnosis of HDM allergy (p=0.003). To avoid missed diagnosis of AR and BA, particularly regarding  the HDM allergy, application of IDST may be beneficial; therefore, IDST should be considered as the next step after SPT for diagnosis of allergy prior to in vitro or provocation tests.