Dear CHNS data users,
Since
we released the biomarker data collected in 2009, many users are
excited to explore the data and of course have some questions. Assuming
you may have
the same question, I make a response to the mailing list instead of
emailing one by one.
To better understand the biomarker dataset, you may need to review the codebook first, which is available at http://www.cpc.unc.edu/
For documentation, please visit http://www.cpc.unc.edu/
In general, each biomarker has a set of 8 variables. Take Y48_1 (blood glucose) as an example:
Y48_1: Blood glucose measured in mmol/L in the field
Y48_1CD:
Whether or not glucose levels are within normal range (.=missing ;
0=normal; 1=abnormal high but within linearity; 2=abnormal high and
beyond linearity;
99=status unknown because age/gender is missing)
Y48_1CS: Whether or not glucose data are available for the participants(.=missing; 1=assay available)
Y48_1SD: At which level the glucose value is (.=missing; 0=within +/- 3 standard deviations; 2=above 4 SD; 3=blow -3 SD)
Y48_1MG: Blood glucose measured in mg/dL in the field
Y48_1MG_CD: same as Y48_1CD
Y48_1MG_CS: same as Y48_1CS
Y48_1MG_SD: same as Y48_1SD
Some
biomarkers were measured twice: one in local hospitals in the field
(labeled as Field) immediately after blood samples were drawn; and one
in the central
lab in China-Japan Friendship Hospital (labeled as CJFH) after frozen
samples were shipped to Beijing and unthawed. Generally speaking,
biomarkers measured in the field were named with a prefix Y, and
biomarkers measured in the central lab were named in a
way that people can easily recognize them, e.g. glucose, urea, HDL,
etc.
In
analysis, if you use glucose, we recommend that you use glucose
measured in the field as blood glucose may depreciate when frozen and
unthawed. For other
biomarkers, we prefer to use those measured in the central lab as they
were measured by the same people with the same machine.
Thank you for your interest in our study.
Happy Holidays.
Shufa Du
Research Assistant Professor
123 W. Franklin Street
University Square East, CB# 8120
Chapel Hill, NC 27516
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