[Correlation and interconversion between erythrocyte cholinesterase values obtained by the Michel and the EQM techniques].
BACKGROUND
Several techniques are available to measure red cell cholinesterase; therefore, evaluations with several methods provide a measure of concordance.


OBJECTIVE
An equation was formulated to transform native data of reference values to reference units of cholinesterase activity as measured by Michel and EQM tests.


METHODS
The experimental design was descriptive, transversal and prospective. The group sampled was a representative adult working population, aged 18-75, without previous exposure to cholinesterase inhibitors pesticides. The individuals were affiliated to the Social Security System and resided in Valle de Aburrá and Cercano Oriente Antioqueño (Antioquia Province, northwestern Colombia).


RESULTS
Of 827 individuals, quantitative erythrocytes (Michel y EQM) tests exhibited "r" coefficients between 0.67 and R2 coefficient of 44%.,This indicated that one test explained the results in other test in 44% of the cases. The corelation was higher in Aburrá than in Oriente. The linear model for the 827 individuals was as follows: EQM U/g oxy-hemoglobin = 9.575 U/ g oxy-hemoglobin + 29.791 (Michel delta pH/hour). Michel delta pH/hr = 0.3312 delta pH/hour + 0.0149 (EQM U/g oxy-hemoglobin), where EQM was expressed in U/g oxy-hemoglobin and Michel pH change/hr. Inter-sections (coefficient a) and inclines (coefficient b) were significant in this model. In the adjusted equations, after exclusion of 12 extreme data (1.5% of 827), the r coefficient increased from 0.67 to 0.72 The adjusted equations were as follows: EQM U/g oxy-hemoglobin = 8.1884 U/g oxy-hemoglobin + 31.3920 (Michel delta pH/hour); Michel delta pH/hr = 0.2925 delta pH/hr + 0.0161 (EQM U/g oxy-hemoglobin).


CONCLUSIONS
This system of linear equations permitted the transformation of Michel (delta PH/ hr) units to EQM (U/g oxy-hemoglobin) units and vice versa. This will facilitate data comparisons by clinicians and epidemiologists who are using these methods of cholinesterase measurement.
Carmona-Fonseca
Jaime
J
Grupo de Malaria, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia. jaimecarmonaf@hotmail.com
D000110:Acetylcholinesterase / Q000032:analysis*; D000293:Adolescent; D000328:Adult; D000368:Aged; D019411:Clinical Laboratory Techniques; D003105:Colombia; D003430:Cross-Sectional Studies; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results
D000110:Acetylcholinesterase