Variáveis biológicas e metodológicas que influenciam na determinação do colesterol HDL

Abstract

Cardiovascular diseases are one of the main causes of death in Brazil and in the world, and considering the increase in serum concentration of high-density lipoprotein (HDL) as a protective factor against these diseases, the objective of this study was to evaluate whether the laboratory methods used for HDL dosage, direct method and precipitation method, beyond the biological factors of a group of employees of the Federal University of Rio Grande do Norte, interfere with the results obtained from serum HDL cholesterol concentration. In addition, to assess whether there was a difference in HDL concentrations by different methodologies in man and woman and age groups, in addition to compare whether the number of patients classified within the reference value group and therapeutic target of the lipid profile is the same in both methods, and finally, to verify whether the same patient is classified as having dyslipidemia due to low HDL cholesterol concentration when evaluated by the two methods. The samples were collected from 29 fasting individuals for biochemical measurements of the lipid profile: triglycerides, total cholesterol, LDL cholesterol and HDL cholesterol, with HDL being measured using two methodologies, direct and precipitation methodology. The concentration of HDL cholesterol was higher when assessed by the direct methodology in patients in general, as well as when evaluated between genders, man and woman, between age groups, 30-39 years old, 40-49 years old and 50-60 years old. The HDL cholesterol concentration was higher when it was determined by the direct methodology for patients in general, and when it was evaluated in the gender and age groups. Patients in general had a mean of 50,0 mg/dL in the direct method compared to the mean of C-HDL of 38,2 mg/dL by the precipitation method. It was observed significant differences (p≤0,05) between the methods, with a difference of 11,8 mg/dL. It was verified significant differences (p≤0,05) between the gender, in which the difference between the methods for the female group was 13,08 mg/dL (p≤0,05), and in the male group was 10,52 mg/dL (p≤0,05). Independent of the methodology, the female group had higher concentrations of C-HDL (direct C-HDL 56,62 mg/dL and C-HDL precipitation 43,54 mg/dL) compared to the male group (C-HDL direct 44,40 mg/dL and C-HDL by precipitation 33,87 mg/dL). It was verified a significant difference (p≤0,05) between all established age groups, between 30 and 39 years old, the difference between the methods was of 9,65 mg/dL, between 40 and 49 years old, the difference was 12,41 mg/dL, and between 50 and 60 years old, the difference between the methods was 13,19 mg/dL (p≤0,05). There was a difference in the number of patients who were included within the reference value and therapeutic target of the lipid profile (HDL ≥ 40 mg/dL). The direct method was 66% (n=19) of the participants, and the precipitation method was 45% (n=13). The same patient included in the group of dyslipidemia due to isolated HDL cholesterol reduction by the direct method (n=10) was also included in this group by the precipitant method, but not all individuals classified as having dyslipidemia by the precipitant method (n=20) had dyslipidemia by the direct method. By analyzing the data, it was possible to conclude that the different methodologies for measuring HDL cholesterol provide different results and the number of individuals classified with dyslipidemia due to low concentration of cholesterol HDL is greater when using the precipitant method. The same individuals, independently of gender, who have dyslipidemia due to isolated HDL reduction using the direct method also have dyslipidemia when HDL cholesterol was measured using the precipitant method, but the contrary was not observed. That way, it is possible to affirm that different methods for dosage HDL cholesterol direct and precipitate, and sex and age of the individuals, offers difference in the obtained results. Therefore, it is essential to create appropriate reference values for each method (direct and precipitant) that are validated by Brazilian Society of Dyslipidemias and standardized in the reports of clinical analysis laboratories in Brazil.