Original Article
Simplified 10-Year Absolute Fracture Risk Assessment: A Comparison of Men and Women

https://doi.org/10.1016/j.jocd.2010.02.002Get rights and content

Abstract

A simplified (semiquantitative) approach developed by the Canadian Association of Radiologists and Osteoporosis Canada (denoted as CAROC) for absolute fracture risk assessment incorporates age, sex, prior fragility fracture, and systemic corticosteroid use, together with bone mineral density (BMD) to define absolute fracture risk. The CAROC system has been shown to predict fracture rates in women referred for clinical BMD testing, but it is uncertain how this system performs in routine clinical practice in men who are much less likely to undergo BMD testing with potential for referral biases. Thirty-six thousand seven hundred and thirty women and 2873 men aged 50 yr or older at the time of baseline BMD testing were identified in a database containing all clinical dual-energy X-ray absorptiometry test results for the Province of Manitoba, Canada. Population-based health service records from 1987 to 2008 were assessed for fracture codes and medication use. Fracture risk under the CAROC model was categorized as low (<10%), moderate (10–20%), or high (>20%). Ten-year fracture risk estimated by the Kaplan-Meier method showed the same gradient in observed fracture risk for men and women. Despite evidence of greater referral bias in men resulting in a higher rate of clinical risk factors, the performance of the prediction algorithm was not affected.

Introduction

Osteoporosis is a common condition in Canada, affecting up to 16% of women and 7% of men older than 50 yr (1). Worldwide, the number of fracture sufferers in 2000 was estimated at 56 million, with approx 9 million new osteoporotic fractures each year (2). Moreover, the case fatality rate for hip fractures can exceed 20% 3, 4, and all osteoporosis-related fractures can lead to significant long-term disability and decreased quality of life 5, 6. The ability to accurately gauge fracture risk is critical in identifying cost-effective thresholds for intervention 7, 8.

A simplified (semiquantitative) approach developed by the Canadian Association of Radiologists and Osteoporosis Canada (denoted as CAROC) incorporates age, sex, prior fragility fracture, and systemic steroid use, together with bone mineral density (BMD), to define absolute fracture risk (9). Under the CAROC system, an individual's 10-yr absolute fracture risk (combined risk for fractures of the proximal femur, vertebrae, forearm, and proximal humerus) is stratified into 3 10-yr absolute fracture risk zones designated as low risk (less than 10%), moderate risk (10–20%), and high risk (greater than 20%).

We have previously reported fracture rates under the CAROC system in women referred for clinical BMD testing (10). It is uncertain how this system performs in routine clinical practice in men, because men are much less likely to undergo BMD testing, which could introduce selection biases because of unusual or unmeasured risk factors. The current analysis specifically addressed this question in an expanded clinical database with longer follow-up that allows for direct estimation of 10-yr fracture outcomes.

Section snippets

Patient Population

The population for this retrospective historical cohort study consisted of all women and men aged 50 yr or older at the time of baseline dual-energy X-ray absorptiometry (DXA). Subjects were required to have results for the lumbar spine and proximal femur (total hip, femur neck, and trochanter sites) between May 1998 and March 2007 with medical coverage from Manitoba Health during the observation period, starting April 1987 and ending March 2008. As earlier software versions before May 1998 did

Results

The study population included 36,730 women and 2873 men (combined: 39,603). Baseline characteristics are summarized in Table 1. On average, men were slightly older than women. Men also had a greater prevalence of the major clinical risk factors that contribute to the CAROC algorithm: prior osteoporotic fracture and recent corticosteroid use. Men were much less likely than women to have used an antiosteoporotic medication in the year before BMD testing. Using sex-specific reference data, mean

Discussion

We found that 10-yr fracture risk prediction under the CAROC algorithm performs similarly in men and women. Despite evidence of greater referral bias in men resulting in a higher rate of clinical risk factors, performance of the prediction algorithm was not affected. This suggests that the major risk factors for fracture are captured with this algorithm, and that other systematic biases are probably weak. Unfortunately, the number of men with the clinical risk factors used in the CAROC system,

Acknowledgments

The authors are indebted to Manitoba Health for providing data (HIPC File No. 2007/2008-35). The results and conclusions are those of the authors, and no official endorsement by Manitoba Health is intended or should be inferred. This article has been reviewed and approved by the members of the Manitoba Bone Density Program Committee.

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    Disclosures—William D. Leslie: In the past 3 yr, W.D.L. has received speaker fees from Merck Frosst Canada Ltd. and unrestricted research grants from Merck Frosst Canada Ltd; Sanofi-Aventis; Procter & Gamble Pharmaceuticals Canada, Inc.; Novartis; Amgen Pharmaceuticals Canada, Inc.; innovus 3M; and Genzyme Canada. He has served on advisory boards for Genzyme Canada; Novartis; and Amgen Pharmaceuticals Canada, Inc. Lisa M. Lix: In the past 3 yr, L.M.L. has received unrestricted research grants from Amgen Pharmaceuticals Canada, Inc., and innovus 3M.

    Sources of support: None.

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