IVD Technology Magazine | IVDT Article Index
Originally published March 1996
Scientists debate means, efficacy of osteoporosis assays
Metra Biosystems, Inc. (Mountain View, CA), is banking on a big demand for finding bone problems among aging baby boomers. It has FDA clearance to market its Pyrilinks-D urinary assay, which it is promoting as a detector of bone loss. The technology relies on the measurement of levels of free deoxypyridinoline cross-links.
Another urine test to detect skeletal deficiency, Osteomark, hit the U.S. medical market last spring and has been making inroads ever since, despite a strategic partnership gone awry between its maker, Ostex International, Inc. (Seattle), and Boehringer Mannheim Corp. (BMC; Indianapolis). The two are now embroiled in federal arbitration hearings: Ostex terminated its licensing agreement with BMC last year, and BMC's parent company, Corange International, Ltd., responded by claiming breach of agreement. The matter is expected to be resolved sometime this year.
Most of the bone-specific assays, including others being developed, tend to fall into one of two categories: tests that measure compounds integral to bone formation, such as alkaline phosphatase and osteocalcin, and those that measure constituents associated with resorption (see Figure 2).
Representatives of NovaDx International, Inc. (San Diego), are at work on a blood-based test that quantifies osteoclasts, the cells associated with bone depletion. They say its accuracy surpasses that of urinary assays for cross-links. "We feel we are developing the second-generation test," says Eric Button, president and chief operating officer of NovaDx.
Scientists in the field say the Metra urine test has the distinct advantages of being less invasive and more patient-friendly than blood tests. Button counters this assertion, saying that patients may be more uncomfortable providing a urine sample than a blood sample. He acknowledges that the NovaDx test is still "at the bench" but points out that the company is making headway in U.S. preclinical trials with Chondrex, a serum arthritis assay manufactured and marketed by Metra Biosystems through a licensing agreement. The osteoporosis kit is on the same track, he asserts.
Dale Greenwalt, PhD, a scientist at Human Genome Sciences (Rockville, MD), has been keeping a close watch on such cell-seeking quantifying techniques as part of his own research. The blood test is based on sound principles, he suggests. Theoretically, the amounts of the bone-forming osteoblasts and the bone- depleting osteoclasts could be analyzed in a formula for tracking or staging disease.
To avoid the risk of infectious disease transmission and the need for a skilled phlebotomist, Pacific Biometrics, Inc. (PBI, Seattle), and BioQuant (Irvine, CA) are developing an innova-tive sweat test for bone loss. Sweat is collected over several days by use of a specially designed skin patch. In addition to being noninvasive, the test, as a result of its collection method, has "the added advantage of averaging out the large day- to-day biological variability plaguing current urine tests," asserts Elizabeth Leary, PhD, vice president and director of laboratories at PBI.
Osteoporosis contributes to 1.5 million fractures annually in the nation and accounts for $10 billion in direct health costs, according to the American College of Rheumatology. By 2020, those costs are expected to at least triple.
But even if precise in vitro bone-measuring methods are available, there are doubts about how much physicians will use them. The American College of Physicians, the largest specialty organization of internists in the United States, doesn't recommend screening for osteoporosis. The National Osteoporosis Foundation does advocate testing, but not by any one method. The American College of Rheumatology supports bone-density measurements to check for the disease; quantitative ultrasound is gaining popularity among this group of physicians. Unlike in vitro tests, ultrasound requires no fluid from the patient.
Still, insists Colette Andrea, vice president of marketing and clinical affairs for Metra, there are compelling arguments for the company's test. "An obstetrician-gynecologist would tell you right now, 'I don't treat osteoporosis. I treat menopause.' But we can say, 'Wouldn't you like to know which bone is likely to fracture?' Physicians want to be able to give concrete evidence of risk. Now they have a quantitative measure."--A. S.
