Elsevier

Journal of Clinical Densitometry

Volume 12, Issue 2, April–June 2009, Pages 158-161
Journal of Clinical Densitometry

Original Article
Variance in 10-Year Fracture Risk Calculated With and Without T-Scores in Select Subgroups of Normal and Osteoporotic Patients

https://doi.org/10.1016/j.jocd.2008.12.003Get rights and content

Abstract

The World Health Organization fracture risk assessment tool (FRAX) uses clinical risk factors to predict the patient's 10-yr probability of sustaining a hip or other major osteoporosis-related fracture. Inclusion of the femoral neck T-score is optional in the calculation. We evaluated the impact of including the T-score in the calculation of fracture risk and resultant treatment recommendation. We retrospectively reviewed charts of 180 white women scanned on a Hologic dual-energy X-ray absorptiometry (DXA). FRAX scores were calculated with T-scores (FRAX+) and without T-scores (FRAX−). We compared the National Osteoporosis Foundation (NOF) treatment recommendations (≥20% risk of a major osteoporotic fracture or ≥3% risk of hip fracture for osteopenic patients) between FRAX+ and FRAX− scores. Agreement between FRAX+ and FRAX− was 89.4%. Disagreement occurred in 2 distinct subgroups of patients (10.6% of cases), that is, FRAX+ scores exceeded the NOF recommended treatment thresholds and FRAX− scores did not, or vice versa. One subgroup comprised older patients with normal T-scores for whom FRAX− scores exceeded the treatment threshold. The second subgroup comprised younger patients with high body mass index (BMI) and low T-scores for whom FRAX− scores did not exceed the treatment threshold. FRAX scores generated without T-scores may lead to treatment recommendations for patients who have normal bone mineral density and no treatment recommendations for patients who have osteoporosis. T-scores should be used for optimal application of FRAX.

Introduction

The World Health Organization recently unveiled the fracture risk assessment tool (FRAX), which is accessible on the Internet and calculates the 10-yr probability of sustaining a fracture using select clinical risk factors with options for including femoral neck T-scores from dual-energy X-ray absorptiometry (DXA) 1, 2. One of the apparent advantages of the FRAX model is that it predicts the absolute rather than the relative fracture risk. This may help patients and clinicians understand and appreciate the seriousness of the illness. FRAX scores may also be used to influence treatment decisions, in much the same manner as T-scores have been used. In fact, the revised National Osteoporosis Foundation (NOF) practice guidelines incorporate use of the FRAX to recommend osteoporosis treatment if the fracture probability is ≥20% or 3% for major osteoporotic fracture or hip fracture, respectively, in osteopenic patients (those with a femoral neck, total hip, or lumbar spine T-score between −1.0 and −2.5) 3, 4.

The NOF guidelines make no specific recommendation about the use of T-scores in the FRAX, except that T-scores must be adjusted before entry in the FRAX (www.NOF.org). Furthermore, the NOF guidelines do not specifically restrict use of the FRAX to patients with osteopenia; however, guidelines recommend that it be used for treatment consideration only in those patients with osteopenia.

Our concern was that it may be tempting to use FRAX scores indiscriminantly as a threshold for treatment without first determining bone status with a DXA scan and establishing classification as normal, osteopenia, or osteoporosis. Thus, we questioned the usefulness of the FRAX model if the T-score is not included in the calculation. In part, this was also based on our concern that payers and regulatory agencies may be tempted to discourage the use of DXA by supporting using FRAX without T-scores. The objective of this study was to compare the fracture risk probability as estimated by the FRAX tool with and without including T-scores.

Section snippets

Methods

The study protocol was approved by the relevant Institutional Review Board. To reduce heterogeneity, only white women scanned on a Hologic Delphi densitometer Hologic Discovery C, Software Version 12.3 were selected for this study from a convenience sample of patients scanned between February 24, 2008 and June 15, 2008. As recommended by the NOF, T-scores were adjusted using the “FRAX Patch” program (www.NOF.org) before being included in the FRAX calculation. Risk factors were retrieved from

Results

Overall agreement between FRAX+ and FRAX− was 89.4%. Scores exceeded the threshold for treatment for 55.6% of patients with FRAX+ and 53.9% for FRAX− (not significantly different). FRAX+ and FRAX− disagreed with respect to treatment threshold in 10.6% (19 out of 180) patients. Table 1 summarizes these data. In 4.4% of cases, FRAX+ scores did not exceed the threshold to treat, whereas FRAX− scores for these same patients did exceed the threshold to treat; T-scores for these patients were mostly

Discussion

This study shows the impact of including the T-scores in the FRAX calculation of fracture probability and reveals discrepancies between FRAX+ and FRAX− scores that result in different treatment recommendations. Specifically, in 4.4% of patients, FRAX− scores exceeded the NOF threshold to initiate therapy in patients with normal femoral neck T-scores. These FRAX− scores were strongly affected by patient age, the mean age for this subgroup being 71.1 yr. In 6.1% of patients, FRAX− produced scores

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