Objective: To investigate the use of laboratory tests and which factors influence the use in Norwegian out-of-hours (OOH) services.
Design: Cross-sectional observational study.
Setting: Out-of-hours services in Norway.
Subjects: All electronic reimbursement claims from doctors at OOH services in Norway in 2007.
Main outcome measures: Number of contacts and laboratory tests in relation to patients' and doctors' characteristics.
Results: 1 323 281 consultations and home visits were reported. Laboratory tests were used in 31% of the contacts. C-reactive protein (CRP) was the most common test (27% of all contacts), especially in respiratory illness (55%) and infants (44%). Electrocardiogram and rapid strep A test were used in 4% of the contacts. Young doctors, female doctors, and doctors in central areas used laboratory tests more often.
Conclusion: CRP is extensively used in OOH services, especially by young and inexperienced doctors, and in central areas. Further investigations are required to see if this extensive use of CRP is of importance for correct diagnosis and treatment.