title: [Reference values for erythrocyte cholinesterase activity in the working population of Antioquia, Colombia, according to the Michel and EQM techniques].
abstract: OBJECTIVE
  To establish reference values for erythrocyte cholinesterase (EC 3.1.1.7) activity for the active working population of two regions of the department of Antioquia, Colombia, that are located at different altitudes above sea level.
  
  
  METHODS
  We took representative samples from populations of active working persons 18 to 59 years old from two regions in the department of Antioquia: (1) the Aburrá Valley (1 540 m above sea level) and (2) the near east of the department (2 150 m above sea level). We excluded workers who were using cholinesterase-inhibiting substances in their work or at home, those who had a disease that altered their cholinesterase levels, and those who said they were not in good health. We measured the erythrocyte cholinesterase activity using two methods: (1) the Michel method and (2) the EQM method (EQM Research, Cincinnati, Ohio, United States of America). We carried out the measurements with 827 people, 415 from the Aburrá Valley and 412 from the near east region. We compared proportions using the chi-square test and Fisher's exact test. We utilized the Student's t test for independent samples to compare two averages. To simultaneously compare three or more averages, analysis of variance was used, followed by the Newman-Keuls multiple-range test. When the variables were not normally distributed or when the variances were not homogeneous, Kruskal-Wallis nonparametric analysis of variance was used to compare the medians. Three computer software programs were used in the statistical analysis: SPSS 9.0, SGPlus 7.1, and Epi Info 6.04. In all the statistical tests the level of significance was set at P < 0.05.
  
  
  RESULTS
  The average erythrocyte cholinesterase activity value that we found for the studied population by using the Michel method was 0.857 delta pH/hour (95% confidence interval (CI): 0.849 to 0.866), and the average value found through the EQM method was 35.21 U/g hemoglobin (95% CI: 34.82 to 35.60). With the Michel method: (1) the enzymatic activity differed significantly between the two regions, according to the Newman-Keuls test; (2) within each region, the enzymatic activity was significantly higher among males than among females, according to the Newman-Keuls test; and (3) in none of the region-sex strata was there a statistically significant influence of age on the enzymatic activity. Using the EQM method, there were no statistically significant differences by region, sex, or age group.
  
  
  CONCLUSIONS
  The erythrocyte cholinesterase activity values found by the two analytical techniques were significantly higher than the values from outside Colombia that are now being used as reference values in the country, which poses both clinical and epidemiological problems. We recommend that the data from this study be adopted as the reference values in Colombia.
authors.affiliation: Facultad de Medicina, Universidad. de Antioquia. Carrera 51-D 62-29, piso 3, Medellín, Colombia. jaimecarmonaf@hotmail.com
authors.forename: Jaime
authors.initials: J
authors.lastname: Carmona-Fonseca
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods; D002802:Cholinesterases / Q000378:metabolism*; D003105:Colombia; D003430:Cross-Sectional Studies; D004912:Erythrocytes / Q000201:enzymology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012016:Reference Values
chemical_list: D002802:Cholinesterases