Background World Health Organisation (WHO) defines osteoporosis as a “bone mineral density (BMD) that is a T score of <-2.5 SD” [1]. Whether this is specifically in any site is not clear. Most units use an average of L1-L4 or the non-dominant femoral neck or femoral mean with any T score less than <-2.5 indicating osteoporosis. No work has been done looking at whether fewer sites could be measured in order to make a diagnosis.

Objectives To identify any correlations between BMD at different skeletal sites in order to determine whether measuring T scores at individual sites are independently sufficient for the diagnosis of osteoporosis.

Methods Data from male and female patients attending dual-energy X-ray absorptiometry (DXA) assessment between 2004 and 2011 in the North West of England were used for analysis. Overall osteoporosis was defined as the average t score for L1-L4 was <-2.5, femoral neck t score or total hip t score was <-2.5. A correlation matrix was initially carried out to identify whether there is good correlation between the individual T scores from L1-L4 and femoral neck and total hip. Univariate logistic regression was used to estimate the likelihood of osteoporosis in individual site T scores and overall osteoporosis. Receiver operating characteristic (ROC) curves and area under the curve was calculated to determine whether t scores from individual sites are independently predictive for diagnosing osteoporosis.

Results 15,304 patients were included in the study. The mean age of patients was 63.6 years (SD 12.4). 84.3% of patients were female. Correlation between the individual t scores from lumbar vertebra and femoral neck and total hip was highly significant (p<0.001) with best correlation between femoral neck and total hip (0.910). The odds ratio and area under the curve for the univariate regression analysis is shown in Table 1 below.

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Conclusions This study shows that there is good correlation between the different sites of measurement of t scores. Also, specific areas such as the total hip, femoral neck and L2 were found to be the best diagnostic predictors of osteoporosis.

References

1. World Health Organisation (WHO). WHO Scientific Group assessment of osteoporosis at primary care level. [Accessed from: http://www.who.int/chp/topics/Osteoporosis.pdf]

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.3250