[Preanalytical issues].

Preanalytical issues in laboratory medicine have been recognized to be important but not so much effort have been focused to them. Urinalysis is one of the most susceptible examinations to preanalytical issues because urine samples are collected by patients themselves and so is stool examination too. Midstream urine catch is well-known appropriate procedure for many urinalysis. Surface scratching is an appropriate method of stool occult blood testing for colorectal cancer and also strategies to avoid the contact of stool with toilet water is another important technique. We also report a case of abnormal results of creatinine clearance (Ccr) caused by the urine collection apparatus as an example of preanalytical issue.