A detailed description of the study methods in SEARCH has been published(3
). SEARCH is a multi-center study conducting population-based ascertainment of diabetes in youth <20 years in the U.S. in racial/ethnically diverse populations. The study was approved by the local institutional review boards that had jurisdiction over the local study populations.
During the study visit, survey information was collected and blood was drawn fasting under conditions of metabolic stability for measurement of A1c and adipocytokines. Height, weight, and waist circumference were obtained(3
). BMI z-score was calculated using a normalized standard deviation score(4
). Diabetes type was based on health care provider’s report and validated with biochemical markers, including diabetes auto-antibodies and C-peptide in a subset(5
). Of the 3,484 youth registered for SEARCH, 1,156 youth with newly diagnosed diabetes in 2002–2004 aged 3–19 years at diagnosis with complete data were included in this analysis. Race/ethnicity was self-reported using the 2000 U.S. census questions format. Adiponectin and leptin levels were measured using commercially available RIA assays with sensitivities of 1 ng/ml and 85.4 pg/ml, respectively.
Descriptive statistics (means/standard deviations or counts/percents) were calculated for variables of interest. Comparisons were made by diabetes type using t-tests or chi-squared tests for continuous and categorical variables, respectively. Next, a series of general linear models were fit to estimate mean levels of adipocytokines and ALR in type 1 and type 2 diabetic youth, adjusted for demographic factors, A1c, and obesity. In these models, because leptin and ALR were highly skewed, data were log transformed to make these variables more normally distributed. Four sequential models were fit: model 1) unadjusted, model 2) adjusted for age, sex, race/ethnicity, model 3) additionally adjusted for diabetes duration and A1c, model 4) additionally adjusted for BMI-z score and waist circumference. SAS software version 9.1 was used.