Osteoporosis is the most common bone disease in the Western world. It is defined as an age-related bone loss resulting in increased susceptibility to bone fracture. Because prevention and therapy are now possible, detection of patients at risk is essential.

Progress in bone mass measurements has been very marked during the last 10 years, many regions of interest can now be measured precisely and accurately. However, there is no uniformity in reporting and there are great problems in comparing results from one centre to another. The different manufacturers pursue various strategies for the determination of bone mineral density (BMD) with the hardware and software available for densitometry. The measured values are not directly comparable without consideration of the examination modalities.

In July 1990, a European Concerted Action on Quantitative Assessment of Osteoporosis was started to stimulate and coordinate the research for this particular problem. In the research group was incorporated an already existing Working Group on Bone Fracture Analysis using Vibration Technique.

The purpose of the concerted European research action was to improve comparability of bone mass measurements between machines, measurement sites and centres, to establish normative data, and to find out which techniques and regions are the most sensitive and specific for the diagnosis of osteoporosis. It is therefore necessary to adhere to common examination modalities in order to reduce to a minimum technician error.

The main achievements were :

- The establishment of a working relationship between basic researchers, clinicians and companies interested in quantitative assessment of bone mass and bone density.

- The development of COMAC-BME reference materials known as the European Spine Phantom (ESP) and the European Forearm Phantom (EFP).

- The production and agreement of guidelines for standardization of measurements, definitions (precision, accuracy, constancy and linearity), primary quality control, COMAC-BME phantom cross calibration, measuring sites, regions of interest (ROI) and data reporting.

- Based on 823 ESP and EFP phantom measurement forms, it is now clear after statistical analysis that there are not only important differences in bone density values between instruments of the same type and brand from different manufacturers, and between different techniques, but that significant differences in precision, accuracy and stability have been found which could lead to important clinical misinterpretations.

- The development of procedures and equations for interconverting the results of dual X-ray absorptiometry on the equipment of one manufacturer in conjunction with measurements made on the machines of another manufacturer.

- 6905 bone density data were received at the statistical centre on a normal European population and patient groups: spinal osteoporosis, thyroid excess, hip fracture, hyperparathyroidism and corticosteroid treated cases. All these data were collected in a standardized way on instruments calibrated with COMAC-BME European Spine Phantom (ESP) and European Forearm Phantom (EFP). These data are not yet analyzed, results will be available early 1993.

- The European phantoms and the European guidelines are at present used as a research tool in Japan (Prof. Orimo) and in the USA (Prof. Genant).

- A major achievement is that the manufacturers from the USA and Europe, of dual energy X-ray absorptiometry equipment (DXA) (USA: Lunar, Norland, Hologic; France: Sopha) and quantitative computer tomography (QCT for the spine, Siemens, IGE and Philips) and for the forearm (Stratec and Densiscan) have given their collaboration and expressed their willingness to adapt their instrumentation along the lines of the research results which will come out of this COMAC-BME project.

- Subgroup COMAC-BME II 2.6 Monitoring Fracture Healing, concentrated their activities on intact bone quality assessment and osteoporosis. Their results dealing with new techniques, experiments, studies on bone properties and the correlation with measurement parameters are published in “In vivo assessment of bone quality by vibration and wave propagation techniques, part II, 1992” (G. Van der Perre, G. Lowet, A. Borgwardt Christensen (Editors)).