title: The potential impact of incomplete radiography histories in epidemiologic studies that rely on prepaid health plan records.
abstract: Members of prepaid health plans are often considered a group for which complete histories of exposure to medically-related risk factors are known. In a population-based case-control study of radiography as a risk factor for acute myelogenous leukemia, extensive retrospective exposure data from an average of 71% of subjects' health care providers were collected. It was determined that at least 21% of prepaid health plan members received diagnostic imaging procedures outside of their plans over the 10-y period of interest and that these "outside" procedures constituted 43% of their total red bone marrow dose from all radiographic imaging. Procedures significantly more likely to have been received outside of prepaid health plans were conventional spine x rays (p = 0.004) and coronary angiograms (p < 0.0001). All "outside" coronary angiograms and 50% of "outside" spine x rays were received at hospitals. Epidemiologic studies that restrict exposure to that received within prepaid health plans may miss a substantial portion of exposure, resulting in underestimated risk estimates and a loss of statistical power.
authors.affiliation: Statology, Rocklin, CA 95765, USA. jpogoda@statology.com
authors.forename: Janice M
authors.initials: JM
authors.lastname: Pogoda
authors.forename: Susan
authors.initials: S
authors.lastname: Preston-Martin
mesh_terms: D000328:Adult; D000368:Aged; D001853:Bone Marrow / Q000528:radiation effects; D016022:Case-Control Studies; D015981:Epidemiologic Factors; D005260:Female; D006125:Group Practice, Prepaid; D006801:Humans; D007348:Insurance, Health; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011834:Radiation Monitoring; D011859:Radiography / Q000009:adverse effects*; D012307:Risk Factors; D013997:Time Factors