There are also problems encountered in standardising the test. The patient should be fasted and must travel to clinic for the test in the morning. The OGTT, if done at hospital, can therefore affect an individual's time off work, time off school, can cause inconvenience and expensive for an individual, parent and child to travel to clinic. The unpredictability of workload for hospital staff means that test times are often not strictly adhered to or accurately recorded. In patients with cystic fibrosis there is also an additional risk of cross infection when they attend the hospital for OGTT. These factors limit the uptake of OGTTs for screening in children with cystic fibrosis.