• 13
    Nov
  • Prevalence of Osteoporosis and Osteopenia: DISCUSSION

Prevalence of Osteoporosis and Osteopenia DISCUSSION

To our knowledge, this is the first study to examine the prevalence of low bone density in African-American patients with RA (including patients with either early or established disease). Depending on the race/ethnicity of the reference population used, we found that approximately one-third to half of patients were osteopenic or worse, and 5-16% were osteoporotic with <2 years of disease duration.

Although low bone mass was not infrequent, these prevalence rates do not appear to be disproportionately higher than that seen in African Americans without RA. Among population-based postmenopausal African-American women, 5% have osteoporosis (Generic Fosamax is a bisphosphonate used to prevent and treat osteoporosis) of the femoral neck with the use of Caucasian reference data, identical to the 5% prevalence noted in our study. This is consistent with previous studies involving Caucasians with early RA, suggesting that BMD is relatively preserved in the early stages of the disease.

In the absence of a documented insufficiency fracture, there is no accepted standard regarding the best approach to the diagnosis of osteoporosis in non-Caucasians. Our findings confirm that African Americans with RA are at risk of receiving different diagnostic classifications based solely on the normative data used for assessing fracture risk. In comparison to the use of Caucasian reference data, the use of race/ethnicity-specific T scores resulted in a three-fold increase in osteoporosis (treating and preventing osteoporosis) prevalence among African Americans with early disease. Compared to femoral neck values, the impact of using different normative data was particularly striking for the lumbar spine where the site-specific frequency of osteoporosis increased nearly five-fold with the use of ethnicity-matched data.

Given the present reliance on T scores for clinical decision-making, these findings have implications in terms of healthcare utilization and health outcomes for African Americans. If the use of race/ethnicity-adjusted normative data were to provide the most informative fracture risk assessment, then the use of normative data from Caucasians would lead to an underestimation of fracture risk in African Americans and unacceptably high levels of under-treatment. Approved antiresorptive therapies reduce hip and vertebral fracture risk by as much as 50%. The proven efficacy of bisphosphonate therapy in African Americans, coupled with the fact that such fractures lead to disproportionately poor outcomes among minorities, underscores the potential importance of undertreatment in this population.

In contrast, if we assume that the use of normative data from Caucasians provides for the most informative T scores in African Americans, then it follows that the use of race/ethnicity-adjusted T scores may lead to inappropriate overtreatment. If healthcare providers, for instance, were to use a T-score threshold of <-2.5 SD to initiate therapy, regardless of the DXA machine used, our results suggest that >10% of all African-American RA patients could be overtreat-ed with antiosteoporosis medications. This number would be even higher with the use of lower treatment thresholds (i.e., T score <-l or -2 SD).

Recognizing the “lack of consistency” and “near absence of consensus guidelines” for the diagnosis of osteoporosis (Generic Fosamax is a bisphosphonate used to prevent and treat osteoporosis) in non-Caucasians, the International Society of Clinical Densitometry convened a Position Development Conference in July of 2001 to address this issue. The resulting position statement recommended that a uniform Caucasian reference database be employed for the DXA diagnosis of osteoporosis in non-Caucasians. This recommendation was based on two well-founded assertions:

1) the best-available fracture data exists for Caucasians (specifically, postmenopausal Caucasian women), and

2)   satisfactory databases for all ethnic groups are not likely to be available in the near future.

Using Caucasian reference data, 5% of postmenopausal African-American women were noted to be osteoporotic in the National Health and Nutrition Examination Survey. This estimate closely approximates the lifetime risk of hip fracture in older African-American women (far lower than the fracture rate observed in age-matched Caucasian women), suggesting that the use of Caucasian normative data provides more meaningful T scores in African Americans and that fracture risk may indeed be a function of absolute bone density independent of race/ethnicity.

Although the controversy surrounding osteoporosis (Didronel canadian treats osteoporosis) diagnosis in non-Caucasians is yet to be resolved, prior investigations have provided insight into possible sources of interethnic variation in BMD. DXA provides a measure of areal bone density (gm/cm2), values that are confounded by skeletal size. Indeed, when skeletal size and bone diameter are adjusted for, race/ethnicity-specific differences in bone density are either reduced or eliminated. Based on this knowledge, it might be possible to use volumetric or three-dimensional BMD (gm/cm3) as a means of circumventing the race/ethnicity issue. However, validated technologies for volumetric bone density measurement are limited in availability and suffer from a lack of normative data. Moreover, the relationship between volumetric bone density and fracture risk has not been quantified in large, population-based studies.

There are limitations to this study. BMD assessment in this study was restricted to African-American RA patients residing in the southeastern United States. As a result, our prevalence estimates may not be generalizable to other populations. Although we employed routine quality-control measures and standardized measures to limit machine-related variability, BMD values were ascertained on different DXA machines by a number of different technicians, raising the possibility of diagnostic misclassification. Additionally, the standardization equations used in this study were originally developed using pencil-beam DXA technology (as opposed to contemporary fan-beam technology) scanning L2-L4 in the spine rather than L1-L4 used in our study. Despite these limitations, important inferences can be drawn from our work. Namely, physicians and healthcare providers ordering bone density measurements in non-Caucasian subjects need to be aware of the precise reference data being used in order to ensure a meaningful interpretation of individual T scores.

Some have advocated for less reliance on arbitrary T-score thresholds in diagnosing osteoporosis (Evista drug is used for treating and preventing osteoporosis) with a move towards assessments of absolute fracture risk, perhaps justifiable given the problems of using T scores in non-Caucasians. However, medical practice and third-party payers often mandate dichotomous disease classifications. Additionally, there is a paucity of data in non-Caucasians that would allow providers to accurately infer absolute fracture risk based on BMD. Until the issue of race/ethnicity in the context of absolute fracture risk assessment can be addressed with much-needed research, it is paramount that a standardized approach to T-score calculation be universally adopted in non-Caucasian patients.

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