Although meta-analyses provide summary effect estimates that help advise patient care, patients often want to compare their overall health to the general population. The Harvard Cancer Risk Index was published in 2004 and uses risk ratio estimates and prevalence estimates from original studies across many risk factors to provide an answer to this question. However, the published version of the formula only uses dichotomous risk factors and its derivation was not provided. The objective of this brief report was to provide the derivation of a more general form of the equation that allows the incorporation of risk factors with three or more levels.
From the aCentre for Clinical Epidemiology, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Canada
bAlvin J. Siteman Cancer Center and Department of Surgery, Washington University School of Medicine, St. Louis, MO
cDepartment of Mathematics and Statistics, McGill University, Montreal, Canada.
Submitted June 26, 2017; accepted March 9, 2018.
The authors report no conflicts of interest.
Correspondence: Ian Shrier, MD, PhD, Centre for Clinical Epidemiology, Lady Davis Institute for Medical Research, Jewish General Hospital, 3755 Cote Ste-Catherine Road, Montreal, QC H3T 1E2. E-mail: firstname.lastname@example.org.