Inadequacy of primary health care test request guidelines--lack of an evidence base.

Patients have high expectations that blood tests be performed and have little understanding of the limitations of testing. 3 The frequency of test ordering is much higher in the USA and Canada, for example, than in the UK, without any overt difference in the quality of care. There are suggestions that 30 - 50% of tests are unnecessary, and that about 15% of abnormal results are not acted upon. 4