Validation of the Dutch guidelines for dual X-ray absorptiometry measurement

Abstract

In Europe, a case-finding strategy for osteoporosis is recommended above widespread population-based screening. However, no universally accepted policy currently exists. In 2005, the Dutch College of General Practitioners published guidelines for GPs to select patients for dual energy X-ray absorptiometry (DXA). AimTo evaluate the sensitivity, specificity, and predictive value of the Dutch guidelines to select participants with osteoporosis for DXA. Design of studyCross-sectional. SettingA total of 345 females aged over 50 years (mean age = 62 years, standard deviation [SD] = 8.3) and 99 males over 65 years of age (mean age = 72 years, SD = 5.2) of a Dutch general practice. MethodCalculation of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the Dutch case-finding instrument for selecting patients with osteoporosis for DXA measurement. ResultsSensitivity was 19.5%, specificity 85.6%, PPV 18.6%, and NPV 86.6%. ConclusionThe Dutch guidelines are unreliable in detecting people at risk for osteoporosis. KeywordsDEXA scan; osteoporosis; practice guideline; predictive value of tests; sensitivity and specificity. INTRODUCTIONOsteoporosis is a major public health issue: osteoporotic fractures affect one in two women and one in five men aged >50 years.1 In 2000, the number of osteoporotic fractures in the European Union was estimated at 3.8 million, equalling a financial burden €31.7 billion. It is expected that by 2050, the direct cost of fractures in Europe will exceed €75 billion. 2The annual incidence of fractures in the UK is estimated at 310 000 with costs of €2.4 billion. 3 In the Netherlands over 430 000 patients have osteoporosis 4 and about 83 000 people aged >55 years have a fragility fracture each year. 5Considering the growing incidence, fracture prevention and thus early diagnosis of osteoporosis are of great importance, especially since pharmacological treatment of osteoporosis has been shown to be cost-effective, irrespective of age. 6Diagnosis of osteoporosis is currently based on bone densitometry, usually by dual energy X-ray absorptiometry (DXA). Bone mineral density is widely recognised as a major predictor for fractures. 7 However, case-finding strategy has been shown to be more cost-effective than population-based NA Verdijk, MSc, PhD candidate; VJ Pop, professor of primary care, the

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“…According to tools such as the FRAX, which have been designed to estimate fracture risk based on the presence of CRFs, fracture risk increases when more CRFs are identified. A possible explanation for our finding could be that the specific CRFs included in the Dutch case-finding method are not very sensitive for identifying subjects at high risk for fractures, since it has already been shown that this method is not very sensitive when selecting patients with osteoporosis [26]. However, the aim of this study was to asses the prevalence of unknown VFs in women aged 50 years and older in Primary care.…”

Risk factors for osteoporosis, falls and fractures in hereditary myopathies and sporadic inclusion body myositis — A cross sectional survey

“…The gold standard in the diagnosis of osteoporosis and its precursor osteopenia is the DXA scan [14], [15]. However, in the present pilot study we confined the design to the collection of data on classical risk factors of reduced bone mineral density, serum levels of 25-OH D3, calcium, and the bone formation marker ALPs.…”

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A fractured service: the latest advice on osteoporosis

“…6 In this issue of the BJGP a Dutch team examines a case finding tool that is widely used in general practice in the Netherlands to select patients for referral for DXA (dual energy X-ray absorptiometry) scanning. 7 Specificity was found to be high (85.9%) but sensitivity was very low (19.5%). The team concluded that the tool 'is of little value to select patients for DXA measurement' and that the Dutch case finding instrument showed the poorest outcomes of the eight tools compared.…”