Calibration and seasonal adjustment for matched case-control studies of vitamin D and cancer.

ABSTRACT: Vitamin D measurements are influenced by seasonal variation and specific assay used. Motivated by multicenter studies of associations of vitamin D with cancer, we formulated an analytic framework for matched case-control data that accounts for seasonal variation and calibrates to a reference assay. Calibration data were obtained from controls sampled within decile strata of the uncalibrated vitamin D values. Seasonal sine-cosine series were fit to control data. Practical findings included the following: (1) failure to adjust for season and calibrate increased variance, bias, and mean square error and (2) analysis of continuous vitamin D requires a variance adjustment for variation in the calibration estimate. An advantage of the continuous linear risk model is that results are independent

SUBMITTER: Gail MH 

PROVIDER: S-EPMC4853926 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature