Primary care practices will be allocated and randomized to either the intervention or control group. Physicians in PCPs randomized to the intervention will be offered order sets based on indication when using the CPOE for ordering laboratory tests. The effect of order sets will be analyzed for 17 common indications for ordering laboratory tests in Belgian primary care: diabetes mellitus, hypertension, cardiovascular disease, general check-up, unexplained fatigue, anemia, liver pathology, medication monitoring, gout, chronic kidney disease, lung embolism, acute coronary syndrome, diarrhea, thyroid disease, sexually transmitted disease, rheumatoid arthritis and obesity.