Validity and recall of information from questionnaires concerning respiratory infections among schoolchildren

The aim of the study was to assess the reliability of questionnaire information on visits to a physician and the use of antibiotics taken for respiratory infections among schoolchildren attending a water-damaged school and a reference group of schoolchildren attending an undamaged school. Two similar questionnaires on respiratory morbidity in two consecutive years were sent to the parents. The information given on the questionnaires was compared with the patient's records of the local health centre. Although the overall total numbers of ambulatory visits in the patients' records and questionnaires seemed to indicate good reliability, a more detailed individual investigation showed poor recall validity from the questionnaires, including a high percentage of unreported visits to the local health centre from both schools. Underreporting was commoner in the control school than in index school. Recall was best for the children who had no visits to a doctor. Use of antibiotics had a better recall than ambulatory visits in both schools. The study indicates that information on health services in questionnaires is not reliable, at least when occurrences in a period of one year or more are evaluated. The use of patient records as a reference of accuracy is also unreliable, unless all the health care services available to the people in the community are covered.