P141 What are the predictors of fragility fracture in patients with low body mass index: an observational cohort study

Abstract

Abstract Background/Aims Low body mass index (BMI) is known to be associated with increased risk of fracture and therefore measurements of height and weight contribute towards the Fracture Risk Assessment Tool (FRAX) score, an estimation tool used to calculate approximate risk of fracture to guide therapy decisions. However, data is lacking on which measurement of bone mineral density is best in those that are underweight. Using a large population of patients with low BMI, we aimed to determine which measurement of bone mineral density (BMD) is the most accurate predictor of fragility fracture in this group of patients. We also aimed to explore the relationship of other traditional risk factors for fracture in this subpopulation. Methods Data on risk factors for osteoporosis and fragility fractures was collected on patients presenting for BMD estimation at a district general hospital in North West England between June 2004 and October 2016. All analysis was performed on those with low BMI, defined as < 18.5kg/m2. Firstly, univariate logistic regression was performed to assess risk of fracture using BMD for lumbar spine, femoral neck and total hip; as well as smoking, alcohol use, presence of rheumatoid arthritis, history of steroid use and history of hip fracture in a parent. Risk factors were defined as per FRAX. This was followed by multivariate regression of available risk factors, using the best BMD predictor identified from univariate analysis. All models were controlled for sex and age at first scan. Results for continuous variables are reported as beta coefficients and for categorical variables as odds ratios. All results are reported with 95% confidence intervals. Area under ROC curve for each model was calculated. Results 921 of 35,759 patients had a BMI of under 18.5 and were included in analysis. Of these, 88.4% were female, mean age at time of scan was 58.6 years. Results are shown in the table. Conclusion In those with low BMI, BMD of left total hip was the best predictor of fragility fracture. Smoking, alcohol use and history of hip fracture were also associated, but previous steroid use and diagnosis of rheumatoid arthritis was not. Disclosure S.D. Sharma: None. M. Bukhari: None.