Originally Published IVD Technology September 2001
New osteoporosis tests headed to market
Consumers at risk for osteoporosis could gain some useful tools if recently released diagnostic products live up to their promise. For one, Osteometer BioTech (Copenhagen, Denmark) received FDA clearance to market its N-MID Osteocalcin enzyme-linked immunosorbent assay (ELISA) in the United States. This test detects both intact osteocalcin, which is synthesized by the bone-forming cells and is therefore a marker of bone formation, as well as the large N-MID fragment.
Osteocalcin consists of 49 amino acid molecules that are released to circulation from the osteoblasts. Three major breakdown fragments from the molecules have been identified in circulation: the N-terminal fragment, the MID-fragment, and the C-terminal fragment. The C-terminal fragment is extremely labile and very easily cleaved from the rest of the molecule, while the further degradation of the larger N-MID fragment occurs at a much slower rate.
While clinicians expect that diagnostic companies will continue to produce new tests for osteoporosis, they also feel that companies need to continue working on such tests to make them better and more efficient.
"There should and will be more interest in osteoporosis among diagnostic companies, because there are going to be more of these tests done," says Lawrence Raisz, MD, chairman of the scientific advisory board for the National Osteoporosis Foundation (Washington, DC) and program director of the general clinical research center at the University of Connecticut Health Center (Farmington, CT). "So far, none of these tests has received sufficient backing from the research and clinical communities to make their use routine. There's still concern about them. One of the issues is accuracy, and that's particularly true for the osteocalcin test.
"But if this new test turns out to be very accurate and reproducible, then that might increase its use," Raisz adds. "We need to keep working on this area, since it's still in the developmental stage."
Another development in the field was the announcement that Axis-Shield (Dundee, Scotland) had signed an agreement granting Specialty Laboratories Inc. (Santa Monica, CA) exclusive U.S. rights to a gene-based test for predisposition to osteoporosis. The company's Osteoporosis GenotypR/Col1A1 test detects changes in the type-1 collagen gene that is associated with predisposition to osteoporosis as well as increased risk of bone fracture. Specialty Labs officials said that they are validating the assay for commercial-scale offering and expect to make it available to physicians and patients during the second half of 2001.
Even once the test becomes available, however, it is uncertain what impact it may have for clinicians."At this point, it has no effect on treatment," says Raisz. "The number of people who have the abnormality in this gene associated with osteoporosis is only moderately large, and this gene is only one of many. Of the various genes that have been proposed as candidate genes, it has probably done as well as any."
According to Raisz, however, even a good candidate gene may not be the ultimate answer for osteoporosis diagnosis. "What's much more likely to have a big impact is multiple-gene analysis—the analysis of multiple genes that might influence a subject's risk of osteoporosis." —Richard Park
Copyright ©2001 IVD Technology
