Reference Values for Serum Total Cholesterol Concentrations Using Percentile Regression Model: A Population Study in Mashhad

Background and purpose: Serum total cholesterol (TC) concentrations are affected by several factors including ethnicity, diet, geographic, and environmental determinants, and are related to another disease, including hypothyroidism, and renal and liver disease. It is associated with an increased risk of cardiovascular disease, particularly if associated with high levels of serum low-density lipoprotein (LDL). The distribution of TC levels within populations may be useful, and the current study aimed to determine the reference values and specific cut points in a population sample from Mashhad, Iran. Materials and Methods: A cross-sectional study was conducted, and data was collected from 6518 individuals (2483 men and 4035 women) aged 25–64 year-old living in Mashhad city using a stratified cluster random sampling design. Reference values for borderline and high TC levels in three age groups were obtained using a percentile regression model. Data were analyzed using Quantreg Software Package and R Ver. 3.1.2 Software. Results: Within the population sample, 38% of the subjects were male and 62% of them were female. The mean and standard deviation for age were found to be 47.07±9 years and 45.28±9 years for men and women, respectively. Percentile regression showed that borderline TC levels for men and women aged 25-64 years were 198-216 mg/dl and 176-243mg/dl, respectively. The values for defining high TC levels were also 226- 239 mg/dl in men and 202 - 271 mg/dl in women. Conclusion: Our study estimated reference values and cut points for borderline and high TC separately in both men and women, and age-related sub-groups for a population derived from Mashhad. These findings could be used in local policy plans to allocate health resources.