Establishing reference values for blood urea nitrogen and serum creatinine in Chinese Han ethnic adult men

The aim was to calculate the two-sided 95th percentile reference values for blood urea nitrogen (BUN) and serum creatinine (SCr) in Chinese Han ethnic adult men.

Serum samples were collected from Chinese Han ethnic adult men aged 20 - 69 years. After screening based on the inclusion and exclusion criteria, a total of 1575 individuals were enrolled in our study. BUN and SCr values were measured on an automatic analyzer (Dade Behring, USA). The data was analyzed and calculated using nonparametric statistical methods.

BUN and SCr values were not normally distributed. The reference values were in the range 3.3 - 7.5 mmol/L for BUN and 64 - 113 micromol/L for SCr. BUN levels were significantly lower in the smoking group than the non-smoking group (Z = -4.52, p < 10(-5)). An increase with age was observed in BUN levels (r(s) = 0.172, p < 0(-5)) and lower SCr levels were weakly associated with the older subjects (r(s) = -0.071, p = 0.005). Moreover, it was found that higher Body Mass Index (BMI) tended toward higher levels of SCr (r(s) = 0.118, p < 10(-5)).

The reference values established for BUN and SCr exhibit a slight deviation compared to those developed in previous studies. We propose reference values of BUN for smokers and non-smokers be constructed, and age- and BMI-specific reference values be applied in clinical laboratories.