Clinical risk factors as predictors of postmenopausal osteoporosis in general practice

Case-finding strategies to identify women with high risk for osteoporotic fractures have recently been proposed, but little information about such an approach in general practice is known.

To study the validity of the proposed case-finding strategy for osteoporosis.

Survey using case-finding strategy.

Seven hundred and twelve women aged between 55 and 84 years, randomly selected from a general practice in The Netherlands.

Of the 712 randomly selected women, 449 women participated. Information was obtained from a questionnaire, direct questioning, and computerised patients files. Bone mineral density of the femoral neck was measured by dual energy X-ray absorptiometry and vertebral morphometry was performed on lateral X-rays of the spine. Osteoporosis was defined by a bone mineral density T-score of less than 2.5 and/or the presence of severe vertebral deformities. Sensitivity, specificity, and predictive values were calculated for the whole set of risk factors; those significantly associated with osteoporosis and in logistic models.

Clinical risk factors were present in 55% of the women and identified 68% of the women with osteoporosis. Three risk factors--a low body mass index, fragility fractures, and severe kyphosis and/or loss of height--were associated significantly with osteoporosis; they were present in 33% of the women and identified 60% of those with osteoporosis. A logistic model based on age and fragility fractures selected 32% of the women and identified 76%.

No single risk factor could assist in identifying women with osteoporosis. A simplified case-finding strategy using only three risk factors, that is suitable for primary care, reduces the number of women to be evaluated by two-thirds; however, this is at the cost of missing the diagnosis in 40% of the women with osteoporosis. Addition of spine radiographs to the case-finding approach helped to obtain a better risk profile of the women and had also practical consequences for the management of some. We propose that radiographs should be included in any case-finding strategy.