Fainting and hemolysis during blood sampling in youngsters: prevalence study.

OBJECTIVE: To assess the incidence of fainting and hemolysis in taking blood samples from adolescents in a school setting. DESIGN: A cross-sectional school-based survey. All blood samples and data were collected during September and October 2005. SUBJECTS: A community sample of 869 youngsters attending third grade secondary education in 14 secondary schools in the Flemish province of Antwerp, Belgium (mean age: 17.3 years, +/-1.2 years). MEASUREMENTS: Fasting blood samples were obtained on-site for measurement of levels of glucose, high density lipoprotein cholesterol and triglycerides. The incidence of fainting and hemolysis was assessed. RESULTS: In 60% of the total sample a blood sample was taken, 15% refused. In the remaining 25%, taking a blood sample was not possible due to problems in drawing blood from the vein (4%) or not fasting (21%). The incidence of fainting was 2.5%. Hemolysis occurred in 2.4% of the blood samples. CONCLUSION: When taking blood samples in this age group, there seems to be a great willingness to participate. Precaution should be taken though when taking blood samples in youngsters. In this study, about 1 in 40 students fainted. When blood samples are taken on-site and transported to a laboratory, an incidence of hemolysis of 2.4% should be taken into account.