Improper or inadequate procedure during blood draw
Failure to comply with Title 17 Administration standards (failure to mix blood with preservative and anticoagulant, for example)
Clotting or coagulating
No chain of custody of blood sample
Contamination (e.g. swabbing skin with alcohol)
Fermentation: formation of alcohol in blood tube after draw and before analysis (e.g. insufficient/incorrect preservative & extraordinary delay between draw & test)