NHG standaard ‘Osteoporose’ heeft weinig nut bij indicatiestelling voor botdichtheidsmeting*

Objective

Assessment of sensitivity, specificity and positive and negative predictive values of the case-finding method of the Dutch College of Practitioners’ (NHG) practice guideline on osteoporosis for the identification of those patients at high risk for osteoporosis who should be referred for bone densitometry. Additionally, the optimal method of risk assessment for osteoporosis in women was determined.

Design

Descriptive.

Method

In one Dutch general practice 444 patients were invited for bone densitometry with dual energy X-ray absorptiometry (DXA). In addition, they were asked to complete a questionnaire on risk factors of osteoporosis in accordance with the case-finding method of the practice guideline. A sum score was calculated from the results of the questionnaire. All patients underwent DXA measurement, although according to the Dutch practice guideline this is only indicated in patients with a sum score ≥ 4 (cut-off score). Using the DXA outcome the sensitivity, specificity, and positive and negative predictive value of the questionnaire for the identification of patients at risk for osteoporosis were calculated. Additionally, in women these values were assessed at lower cut-off points.

Results

A sum score and a DXA measurement were obtained from 290 patients. At a cut-off score of 4, sensitivity was 17% and positive predictive value 14%. In women, the optimal cut-off value was 1, with a corresponding sensitivity of 79%.

Conclusion

The NHG case-finding method has little value in identifying patients at risk for osteoporosis. Sensitivity in women increases when the cut-off score is lowered from 4 to 1. We suggest that the NHG revises its practice guideline on the selection of patients for bone densitometry. This requires further research. The revision should be validated for both women and men before implementation in general practice.