Prevalence of Osteoporosis and Osteopenia: METHODS
Participants were enrollees in the Consortium for the Longitudinal Evaluation of African Americans with Early Rheumatoid Arthritis (CLEAR). Eligible participants self-reported African-American ethnicity, had an established diagnosis of RA as defined by the American College of Rheumatology (ACR) classification criteria and had <2 years of disease duration (from time of symptom onset). All patients underwent a comprehensive physical examination and were asked to provide a detailed medical history. RA disease activity was quantified by a board-certified rheumatologist using tender and swollen joint counts in addition to self-reported disability index scores (measured using the Stanford Health Assessment Questionnaire).
Bone Mineral Density Measurement
BMD measurements of the femoral neck and lumbar spine (L1-L4, anterior-posterior) were performed by trained technicians at each participating center using DXA. Quality control of BMD measurement for this study was provided by Synarc Inc. (Maynard, MA) and included the use of a standardized qualitycontrol phantom for each machine on each day a study patient was scanned and at least three times weekly. Femoral neck and lumbar spine measurements were not obtained on a small subset of patients due to the presence of either bilateral total hip replacements (n=3) or other metal hardware interfering with vertebral measurements (n=2). Given the multicenter design of the study, BMD values were obtained on machines from all three major manufacturers and included Hologic (n=3 machines), Lunar (n=2 machines) and Norland (n=l machine). Viagra Super Active
In order to correct for systematic differences in absolute BMD among the various machine types, measured values were standardized to Hologic BMD using published conversion equations. Application of these standardization formulas has been reported to reduce manufacturer-related variability in bone density to <3%.
Defining Osteopenia and Osteoporosis Prevalence
After the BMD measures were standardized to Hologic values, site-specific T scores were calculated by subtracting the peak referent bone density values from the patient’s observed value. This difference was then divided by the corresponding referent standard deviation. For the spine, we used the manufacturer’s reference database (Hologic Inc., Bedford, MA). For the hip, we employed reference data collected as part of the National Health and Nutrition Examination Survey (NHANES)-III. The peak reference values and corresponding standard deviation (SD) for both African Americans and Caucasians are shown in Table 1. Normative peak BMD values are approximately 1 SD higher (0.09-0.14 gm/cm2) in African Americans than Caucasians at both the hip and spine.
Table 1. Sex-specific bone mineral density values (gm/cm2) for lumbar spine and femoral neck for study patients (n=175) and normative populations
|Mean ± standard deviation bone mineral density values (gm/cm2)|
|Lumbar Spine Men Women||Femoral Neck Men Women|
|Study patients1 1.104 (0.20) Peak normative Caucasians 1.091 (0.11) Peak normative African Americans 1.197 (0.11)||1.084 (0.18) 1.047 (0.11) 1.150 (0.11)||0.879 (0.16) 0.934 (0.14) 1.074 (0.17)||0.848 (0.16) 0.858 (0.12) 0.950 (0.13)|
|* Lumbar spine reference data from Hologic Inc. (Bedford, MA); femoral neck reference data from the National Health and Nutrition Examination Survey (NHANES)-III ; | Participants in the Consortium for the Longitudinal Evaluation of African Americans with Early RA (CLEAR)8’9|
We calculated two T scores for each participant. The first set of T scores was generated using peak sex-matched reference data from Caucasians. We then generated a second set of T scores using peak values from referent sex-matched African Americans. We defined osteopenia and osteoporosis (Didronel canadian treats osteoporosis) using the T-score thresholds established by the World Health Organization for diagnosis in postmenopausal Caucasian women. Based on these thresholds, osteoporosis (Evista drug is used for treating and preventing osteoporosis) was defined as a BMD value >2.5 SD below the young adult mean. Osteopenia was defined as a BMD >1 SD and <2.5 SD below this mean. Patients were classified as having osteopenia or osteoporosis (Drug Fosamax is a bisphosphonate used to prevent and treat osteoporosis) based on their lowest T score. We examined sex differences in site-specific BMD using Students’ t test. Differences in osteopenia and osteoporosis frequency, based on the presence or absence of race/ethnicity adjustment, were assessed using McNemar’s test. All analyses were performed with SAS (SAS Inc., Cary, NC).