INTRODUCTIONCirculating insulin concentrations provide important information for the evaluation of insulin secretion and insulin resistance. Reference intervals are the most widely applied tool for the interpretation of clinical laboratory results. We carried out an analysis of the data available from the Fangchenggang Area Male Health and Examination Survey in order to derive a reference interval for fasting insulin specific to the Chinese population.

METHODSA total of 1,434 fasting serum insulin results were obtained from healthy nondiabetic adult men aged 20-69 years, after taking into consideration the inclusion and exclusion criteria. Serum insulin was measured using electrochemiluminescence immunoassays. Nonparametric statistical methods were used to calculate and analyse the data.

RESULTSThe reference interval for fasting serum insulin for Chinese adults was in the range 1.57-16.32 μU/mL (median 5.79 μU/mL). Significant correlations were found between fasting serum insulin and glucose and diastolic blood pressure (p < 0.001). Statistically significant differences were observed in insulin concentration with respect to age and body mass index (BMI; p < 0.001). Younger people had a higher fasting serum insulin concentration. Increased fasting serum insulin was also found to be associated with BMI.

CONCLUSIONWe established a reference interval for fasting serum insulin in healthy nondiabetic adult Chinese men that is lower than what was previously suggested. BMI and age (but not smoking, alcohol consumption or physical activity) were found to be important factors associated with fasting serum insulin. Our results will help improve the diagnostic interpretation of investigations for metabolic and cardiovascular disorders in a Chinese population.