Statistical analysis
Analyses were performed incorporating the sampling weights to obtain unbiased estimates from the complex KNHANES sampling design following the KNHANES recommendations.
The study population was separated as a subpopulation, and the analysis was carried out on the entire KNHANES samples for 2011 and 2012 to represent all Korean adults without bias.
In addition, weight adjustments were applied to the user-missing values to prevent skews in sampling design.
The demographic and biochemical characteristics of the study population were summarized and compared using the complex samples general linear model for continuous variables and the complex samples chi-square test for categorical variables.
The mean and the 95% confidence interval (CI) were presented for data on continuous variables, whereas unweighted count with weighted percentage was presented for data on categorical variables.
The complex samples chi-square test was used to analyze the prevalence of CKD by GFR with ACR categories, and GFR comparison between MDRD and CKD-EPI equations was expressed as a weighted percentage.
A subpopulation was added to strata when performing the complex samples chi-square test.
Associations of CKD, GFR, and ACR categories with various risk factors, including gender, age, BMI, DM, hypertension, and dyslipidemia were expressed as an odds ratio (OR), which was calculated using complex samples multivariate logistic regression analyses.
All statistical analyses were performed using IBM SPSS version 21.0 (IBM Corp., Armonk, NY, USA). The statistical significance level was set at p < 0.05.