Plantain allergy (Plantago lanceolata): assessment of diagnostic tests.

A study was made of 55 patients with skin prick test results for Plantago lanceolata of 3 mm2 or more. They were evaluated in relation to the response elicited by 10 mg/ml of histamine HCl. Patients with a response to Plantago less intense than the response to histamine were considered as having a "negative" response, whereas those whose response to Plantago was more intense than the response to histamine were considered as having a "positive" response. In 35 cases a radioallergosorbent test (RAST) was performed and in 22, nasal provocative testing (NPT). The frequency of positive response was 0.63 for skin tests, 0.11 for RAST and 0.72 for NPT. Among the patients with positive NPT, the frequencies of positive response to skin tests and RAST were 0.71 and 0.6 (p < 0.05), respectively. Results are discussed and study methods are proposed.