Stability of acetylcholinesterase (AChE) activity in blood: the effect of the preservative agent.

Fluoride anions are believed to inhibit acetylcholinesterase activity, thus there is a possibility that the activity may be affected by blood sampling into vials containing sodium fluoride as an anticoagulant. The paper aims to draw attention to the effect of the anticoagulant used in blood collection tubes on acetylcholinesterase activity. A stability study was conducted for 176 days on blood samples collected into tubes containing sodium fluoride or sodium EDTA. An improved Ellman procedure, utilizing spectrophotometric determination at 436 nm, was employed in order to determine acetylcholinesterase activity. An immediate decrease in acetylcholinesterase activity was observed in blood samples containing sodium fluoride. A significant decrease was evident immediately after blood collection and on the first day, after which the activity stabilized at 84% of the initial value. Subsequently, the activity increased to a level comparable to the initial value. In samples collected with EDTA, acetylcholinesterase activity was comparable to that in the sample without anticoagulant, and the activity remained constant for about 2 months. In conclusion, it is recommended that acetylcholinesterase activity be tested immediately after blood collection to reduce enzyme inhibition by fluoride anions, or that tubes with another anticoagulant, such as EDTA, be used.