Biological variation of serum cholinesterase activity in healthy subjects.

Objectives: Serum cholinesterase (ChE) 3.1.1.8 is measured to assess exposure to organophosphorus pesticides and determine deficiency related to prolonged apnea after the induction of anesthesia with certain drugs and less often as an indicator of liver function. Biological variation (BV) is an accepted endogenous source that contributes to the total variation in laboratory medicine. No data on the BV of serum ChE have been found in the European Federation of Clinical Chemistry and Laboratory Medicine BV database. Thus, this study aimed to contribute to the data on BV of serum ChE activity.

Methods: Detailed inclusion and exclusion criteria were used for the enrollment of 20 (10 women and 10 men, 8-10 weeks) ostensibly healthy volunteers from Turkey. The serum ChE activity was measured on Roche Cobas c501. Statistical analyses included the detection of outliers, control for the normality of distribution, checking steady-state condition, assessment for homogeneity, subgroup analysis, analysis of variance with 95 % confidence intervals, and estimation of analytical performance specifications (APS).

Results: After exclusion, 332 results were included in the study. The within-subject BV of men (3.5 % [2.9-4.2 %]) was lower than that of women (4.8 % [4.1-5.8 %]). Between-subject BV of men and women were 15.9 % [10.5-32.4 %] and 12.3 % [8.4-22.6 %], respectively. The index of individuality was 0.18 and reference change value (RCV) was +9.1 %/-8.3 %. The calculated desirable APS for imprecision and bias were 1.7 and 3.2 %, respectively.

Conclusions: We believe that this study will contribute to the BV data on serum ChE activity. The prominent individuality of serum ChE activity favors the use of RCV instead of population-based reference intervals for more reliable follow-up.