Pre-analytical Variable
Any factor occurring before specimen analysis—such as collection method, transport conditions, or processing delays—that can affect the accuracy of laboratory results.
Full Definition
Pre-analytical variables encompass all conditions and events from test ordering through specimen preparation that may introduce error into laboratory results, independent of the analytical instrument or method. Common pre-analytical variables include patient preparation (fasting status, posture, tourniquet time), specimen collection technique, tube type and order of draw, transport temperature and time, and centrifugation conditions. They account for the majority of laboratory errors and are a central concern in clinical laboratory quality management. The term is typically hyphenated as 'pre-analytical' in both noun and adjective uses, though some style guides permit 'preanalytical' (no hyphen) as an established compound.
Usage
Usage note: Hyphenate 'pre-analytical' consistently. Distinguish from 'analytical variable' (instrument/method error) and 'post-analytical variable' (transcription, reporting errors).
In Context
- "Extended tourniquet application time is a recognised pre-analytical variable that elevates serum potassium values." — Clinical chemistry quality manual
- "The audit identified pre-analytical variables—specifically delayed centrifugation and incorrect tube type—as the primary sources of erroneous coagulation results." — Laboratory quality improvement report