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Activity Number: 115
Type: Topic Contributed
Date/Time: Monday, August 5, 2013 : 8:30 AM to 10:20 AM
Sponsor: Section on Statistics in Epidemiology
Abstract - #307852
Title: Varying-Coefficient Deming Regression (VCDR) and Its Application in Bone Densitometry
Author(s): Ying Lu*+ and Chong Gu and Bo Fan and Selwyn Au and John A Shepherd
Companies: VA Palo Alto Health Care System & Stanford University and Purdue University and University of California, San Francisco and VA Palo Alto Health Care System and University of California, San Francisco
Keywords: Deming regression ; Bone Mineral Density ; Calibration ; Non-linear regression ; Varying Coefficients ; NHANES
Abstract:

Deming regression (DR) has been successfully used to establish cross-calibration (CC) formulas for bone mineral densities (BMD) between manufacturers at several anatomic sites. In a recent study to establish CC for whole body BMD, DR was not used because the relationship between BMDs from Hologic and GE scanners varies with subject's weight, total fat and lean mass. Separate linear regressions were used for people with weight above or below 40 kg (Shepherd et al.,JBMR 2012), which don't meet the self-consistency requirements and discontinue at 40 kg. In this paper, we present a new varying-coefficient DR (VCDR) that allows the intercept and slope be non-linear functions of covariates. Estimation procedures and R programs were developed and applied to derive a consistent calibration formula that varied its coefficients based on covariates. Our results showed this VCDR effectively removed all systematic bias in Shepherd's formulas although the reduction of total calibration error was minimal. This formula can be used to translate the national normative whole body BMD data measured by Hologic scanners in the National Health and Nutrition Examination Study (NHANES) to GE scanners.


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