Poster Number 181 Prevention and Treatmentof Osteoporosis

RISEDRONATE SHOWS CONSISTENT REDUCTION OFTHE RISK OF NEW VERTEBRAL FRACTURES OVERTHREE YEARS IN PROTON PUMP INHIBITOR (PPI) ANDH2-RECEPTOR ANTAGONIST (H2RA) USERS

Robert Lindsay, MD, PhD, Helen Hayes Hospital, West Haverstraw, NY

Jay L. Goldstein, Department of Medicine, University of Illinois at Chicago,Illinois; Xiaojie Zhou, Procter & Gamble Pharmaceuticals, Mason, OH; ChristianRoux, Hospital Cochin, Dept. Rheumatology, Paris, France, Andreas Grauer

Recently, the question was raised whether use of PPIs or H2RAs could interferewith efficacy of bisphosphonates. In this retrospective analysis, we investigatedwhether concomitant use of PPIs or H2RAs affected the efficacy of risedronatein reducing the risk of new vertebral (Vert)-fractures. Intent-to-treat subjects (w/paired evaluable spinal-radiographs) from 3 phase-III risedronate fracture trialswere included. Subjects were classified as PPI or H2RA users if they used eitherat any time during the trial. Endpoint was time to 1st Vert-fracture; time-to-eventmethodology was used (Kaplan-Meier and Cox regression) stratified by trial, ad-justing for the number of prevalent Vert-fractures. Of 5454 subjects, 1276 (23%)used PPIs or H2RAs. At baseline, PPI or H2RA users and non-users were similarin age, BMD, BMI and prevalent Vert-fracture history. However, PPI or H2RAusers had a higher incidence of upper-gastrointestinal (UGI) disease and more sig-nificant comorbidities. Regardless of PPI or H2RA use, compared to placebo,risedronate significantly (p ! 0.05) reduced the relative risk of new Vert-fracture-s(Table). The risedronate treatment effect was consistent across the user and non-user subgroups (treatment-by-status-interaction: pO 0.698). In PPI and H2RAusers we observed higher incidence of UGI-AEs compared to non-users (257% in-creased risk 95% CI 225e293%, p ! 0.001). Risedronate and placebo groups hadsimilar risks for UGI-AEs regardless of H2RA/PPI use (treatment-by-status-inter-action: p O 0.562). It has been hypothesized that PPIs or H2RAs may decrease theabsorption of calcium or bisphosphonates. Within the limits of these clinical trials,this study did not demonstrate an influence of PPI or H2RA use on risedronateefficacy.

Poster Number 184 Prevention and Treatmentof Osteoporosis

INTRA-OPERATOR PRECISION FOR IN VIVO HIGHRESOLUTION PQCT SCANS

Angela M. Cheung, MD, PhD, FRCP(C), Associate Professor, UniversityHealth Network

Claudia Chan, Osteoporosis and Women’s Health Programs, University HealthNetwork; Farrah Ahmed, Osteoporosis and Women’s Health Programs, UniversityHealth Network; Hanxian Hu, Osteoporosis and Women’s Health Programs,University Health Network; Alice Demaras Irene Polidoulis and Lianne Tile

High resolution peripheral quantitative computed tomography (HR-pQCT) isa novel and emerging technique for assessing bone geometry and microarchitec-ture non-invasively, however, little is known about its intra-operator reliability.We prospectively recruited 31 subjects for scanning of the radius and tibia onthe Xtreme CT (Scanco, Sweden) according to standard protocol by one operator.These subjects were re-positioned and re-scanned by the same operator on thesame day. Informed consent was obtained prior to any study procedures, and thestudy was approved by our institutional research ethics board. Twenty-five womenand six men participated in the study. Two of them only had one site scanned.

Mean age was 42.4 years (range: 20e69). The root-mean-square coefficients ofvariation (and least significant change) for the radius and the tibia were: total vol-umetric BMD 0.52% (4.9 mg/cm3) and 0.23% (2.1 mg/cm3), cortical volumetricBMD 0.46% (10.9 mg/cm3) and 0.19% (4.8 mg/cm3), trabecular volumetric BMD0.70% (2.8 mg/cm3) and 0.40% (1.9 mg/cm3), outer trabecular volumetric BMD0.63% (3.9 mg/cm3) and 0.44% (3.0 mg/cm3), inner trabecular volumetricBMD 0.84.% (2.3 mg/cm3) and 0.35% (1.2 mg/cm3), cortical thickness 1.33%(0.029 mm) and 0.50% (0.017 mm), trabecular thickness 4.55% (0.009 mm) and3.73% (0.008 mm), trabecular number 4.78 % (0.252 mm-1) and 4.08%(0.196 mm-1), trabecular separation 4.83% (0.063 mm) and 4.08% (0.062 mm-1); BV/TV 0.71% (0.002) and 0.37% (0.001); and Tb. 1/N. SD 4.90%(0.023 mm) and 3.34% (0.020 mm). In summary, volumetric BMD parametershave excellent precision, similar to those for areal BMD measurements by dual en-ergy X-ray absorptiometry, whereas geometric parameters have higher variation.Observed changes in geometric parameters over time will need to be interpretedwith this in mind.

Poster Number 188 Prevention and Treatmentof Osteoporosis

SHORT-TERM PRECISION OF PERIPHERALQUANTITATIVE COMPUTED TOMOGRAPHY FOR HARDAND SOFT TISSUE MEASUREMENTS AT MID-SHAFT ANDDISTAL REGIONS OF THE TIBIA

Kyle W. Creamer, BS, CCD, Graduate Student, Radiology Technician,Virginia Tech

Katrina L. Butner, Graduate Student, Radiology Technician, Virginia Tech,Blacksburg, VA; William G. Herbert, Professor, Radiology Technician, VirginiaTech, Blacksburg, VA

The pQCT is a novel instrument used for determining volumetric bone density andexploring other parameters of hard and soft tissues of the limbs. The purpose ofthis study was to determine the coefficient of variation (CV) within our lab for var-ious regions of interest (ROI) for the Stratec XCT3000 pQCT scanner. The non-dominant lower leg of 22 pre-menopausal women with widely varying physicalactivity habits (Mean age� SD 39.8� 4.6 yr, BMI 5 25.4� 6.6 kg/m2) werescanned on 3 non-consecutive days using the system s TIBIA4S mask to obtaindata at the 4 and 66% loci, from the distal end of the bone. Analyses weremade using the TIBIA4S macro, supplied by the manufacturer, and the CALCBDand CORTBD functions. CVs were calculated with the ISCD Advanced PrecisionCalculating Tool obtained from their website (http://www.iscd.org/visitors/mem-bers/securefile.cfm?fileID 5 30). CVs for area and density measures of cortical tis-sue ranged from 0.5 to 2.7% and for trabecular tissue from 1.8 to 8.0%. CVs forareal and density measures of soft tissues (marrow, muscle, fat) ranged from 1.7 to13.1%. With the exception of the marrow density from the TIBIA4S macro at66%, acceptable precision with the pQCT was achieved in our setting for theconditions specified. These findings suggest potential for use of the pQCT incross-sectional or short-term serial studies of humans in which hard and soft tissuefeatures of the leg may be of special interest.

466 Abstracts

Journal of Clinical Densitometry: Assessment of Skeletal Health Volume 11, 2008