In laboratory medicine, a test result's accuracy depends not only on the analyser and analytical process but also on the quality of the specimen submitted for testing. Anticoagulant contamination of a serum (or other) sample is an important but often overlooked pre-analytical error that can produce misleading laboratory results, even when the analyser is functioning perfectly and internal quality control is within acceptable limits. Serum samples are generally collected in plain or serum-separator tubes and are allowed to clot before centrifugation. Contamination may occur when additives from other blood collection tubes inadvertently enter the serum specimen. This can happen because of an incorrect order of draw , inappropriate blood transfer between tubes, collection from an intravenous line, improper phlebotomy technique, or accidental use of the wrong tube . Anticoagulants are not simply inert substances. They contain chemicals specifically designed to alter coagulation or pre...