SKARP--A population-based cohort study of childhood food-associated symptoms perceived by parents and food allergies diagnosed by physicians: design, methods and participation.

BACKGROUND: Few epidemiological studies exist on food-associated symptoms and allergies in large unselected child populations. AIMS: To describe the design, methods and participation rate of the South Karelian Allergy Research Project (SKARP), a population-based epidemiological study on food-associated symptoms and physician-diagnosed food allergies.
METHODS: The study population of 5,973 children born between 2001 and 2006 and resident in the province of South Karelia, Finland, was identified from the nationwide population register. The parents received a questionnaire to be returned at their child's annual visit to the child health clinic, where supplementary interviews were performed. Results of allergy tests (skin prick tests, immunoglobulin E antibodies and open food challenges) performed on participants and non-participants were collected from the relevant health care units in the area.
RESULTS: Participation rates in the questionnaire study were 54% (644/1,194) among the parents of neonates and 69% (3308/4,779) among those of the children aged 1 to 4 years. Cooperation with the child health clinics and mailing of a reminder questionnaire improved participation by 8 and 10 percentage points, respectively. The final participation rate seemed to be unaffected by whether the child had or had not been tested for suspected allergy.
CONCLUSIONS: A reasonably good participation rate and almost complete coverage of allergy tests were achieved thanks to successful cooperation with the child health clinics and test laboratories. This baseline study forms a representative database to estimate the occurrence of food-associated symptoms, physician-diagnosed food allergies and allergy testing in the general population.