Total cholinesterase in plasma: biological variations and reference limits.

Factors affecting biological variation in total cholinesterase activity in plasma were studied in a population of 3372 apparently healthy subjects at least four years old. Determination of the dibucaine number, after inhibition of the activity by dibucaine, made it possible to specify the contributions of genetic and physiological characteristics to variations in the total activities by using a statistical method of segmentation. The main factors modifying plasma cholinesterase activity in males are genetic status (dibucaine number) and degree of overweight (subscapular skinfold). In females, hormonal status (puberty or menopause), genetic status (dibucaine number), and the use of oral contraceptives are the factors mainly responsible for the variations of plasma cholinesterase activity. These data allow us to propose reference limits for total plasma cholinesterase.