Verification of self-reported asthma and allergy in subjects and their family members volunteering for gene mapping studies.

Studies which aim at mapping genes contributing to the development of asthma and atopy demand that hundreds of patients and their family members be assessed. In Finland, the Social Insurance Institution (SII) grants substantial reimbursement for medication to all patients who meet diagnostic criteria of asthma, which include a history of asthmatic symptoms and a measured reversibility of bronchial obstruction. To recruit a large number of asthma patients efficiently in a short period of time, we took advantage of the national reimbursement procedure and retrospectively collective data on patients' medical history and lung function test results at the time of diagnosis. First, we wanted to investigate if the reimbursements could be regarded as objective verification for self-reported asthma. Altogether 335 adult self-reported asthma patients were evaluated, 87% of them were verified as having chronic asthma. Reimbursement for medication showed a sensitivity of 95% and a specificity of 76% for verified asthma. Second, we were interested to see if self-reported nasal allergic symptoms or self-reported physician diagnosed allergic rhinitis were sensitive and specific measures of allergy. The self-reported allergic nasal symptoms had a poor specificity (31% in the proband group and 59% in the family members group) when compared to the allergy screening test (Phadiatop). The best verification for self-reported asthma was achieved by combining the information on self-reported disease, granted reimbursement by the SII and the medical records. For allergies, the specificity of self-reporting was far too low to be used alone, and a positive allergy screening test together with relevant symptoms was chosen as a marker of allergy.