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118 SCIENTIFIC AMERICAN June 1991
Clot Spotter Does a test for fibrinogen predict risk of heart disease?
A: if blood pressure, cholesterol , cigarette smoking and weight were not enough, here comes
another potential risk factor for heart disease: fibrinogen. This blood-clotting factor circulates through the body on the lookout for any lesion in need of repair with a clot or scab. But lately the protein has been showing up in studies that link high levels of it to heart disease and stroke.
"There is a great deal of interest in fibrinogen as a risk factor," acknowledges John C. Hoak , director of hematology at the National Heart, Lung and Blood Institute in Bethesda, Md. But, he adds, the plethora of studies making the correlation may be raising unwarranted suspicions. It is still undetermined whether elevated fibrinogen levels actually cause heart disease or are simply associated bystanders.
The scientific uncertainty has not deterred Henry L. Nordhoff, president and chief executive officer of American Biogenetic Sciences (ABS), a tiny biotechnology company on the campus of the University of Notre Dame in Indiana.
"Fibrinogen should be on a routine physical," he asserts, citing independent studies done in the U.S., U.K . and Sweden, which conclude fibrinogen is a risk factor that should be a target of routine screening-and perhaps therapy.
Nordhoff happens to be developing a rapid, highly speCific test for fibrinogen. He hopes a major diagnostic company will license the test, trade named Cadkit, which has been designed to run on the high-volume automatic machines found in clinical laboratories. A bedside version that works on whole blood is also under development. It could be used to monitor heart-attack patients receiving or being considered for clot-dissolving therapy.
One of the studies that puts the onus on fibrinogen is the same one that fingered cholesterol. The Framingham study, which since 1948 has tracked the heart health of residents in the Massachusetts town, measured fibrinogen levels just once, in 1968-among 1,315 people free of cardiovascular illness. It has since found that "if we follow people long enough, those with higher fibrinogen values are at greater risk for atherosclerotic problems," says William B. Kannel, lead researcher for the Framingham study.
The classic way of measuring fibrinogen is with functional assays that add
Starting from Scratch
G ordon Bell is clearly a man after the hearts-and businesses-of aspiring entrepreneurs. In the 1970s he led the design team that built the VAX superminicomputer at Digital Equipment Corporation
in Maynard, Mass. That work helped Digital blossom from a midsize company into one that IBM had to reckon with. Since then, Bell has had a hand in some 20 start-ups, most of which have tried, with varying degrees of success, to build computer hardware.
Now Bell is trying a different kind of start-up, one that aims to guide other start-ups through infancy. He has developed what he calls a diagnostic, a collection of questions he thinks could help fledgling entrepreneurs. Bell's approach is outlined in his recent book, High-Tech Ventures (Addison-Wesley), which reads a bit like a Dr. Spock guide for young companies. Among his questions: Will the company need fewer than three technical breakthroughs to make its product? Do the designers have a manufacturing strategy in mind? Will the product still be trendy when the company seeks additional funding?
Yet building a successful start-up is still more of an art than a science. Some consultants may disagree with Bell's priorities, even on elements as standard as a business plan. Bell argues that such a plan should serve as a dynamic blueprint for the company. In contrast, Edward B. Roberts, a professor at the Sloan School of Management at the Massachusetts Institute of Technology, suggests in his recent offering, Entrepreneurs in High Technology (Oxford University Press), that his studies reveal few relationships between high-tech start-ups, their initial plans and their later performance.
So far, Bell says, Japanese managers have been more intrigued by his approach than have U.S. venture capitalists. All Bell hopes is that his pointers will steer some entrepreneurs away from the pitfalls he has encountered. As he wryly observes: "In hardware engineering, Ohm's law and Maxwell's equations pale in importance and influence next to Murphy's law." -Elizabeth Corcoran
© 1991 SCIENTIFIC AMERICAN, INC
thrombin to a blood plasma sample . . Thrombin converts fibrinogen to fibrin, the main component of insoluble clots. The faster a clot is formed, the more fibrinogen is deemed present. A newer testing approach uses monoclonal antibodies, but the clotting process releases breakdown products that can confuse these immunochemical assays.
ABS is betting on a new production technique to manufacture monoclonal antibodies, which the company claims are much more specific to fibrinogen. Instead of isolating antibody-producing cells from normal laboratory mice, ABS creates its antibodies in mice that have been immunologically isolated for generations.
Because these mice, which the company has licensed from Notre Dame's Lobund Laboratory, have developed very few antibodies on their own, the response is highly specific when they are injected with a specific antigen-in this case, human fibrinogen. ABS says that one in 48 spleen cells from these mice produced antibodies to fibrinogen, compared with one in 60,000 cells from normal mice. The cells are then cultured to provide commercial quantities of the antibody. "Antibodies made this way seem better able to 'see' the dllference between fibrinogen and fibrin," explains Paul E. Gargan, director of protein biochemistry at ABS.
Given an accurate test, patients with high fibrinogen levels could minimize other risk factors, such as smoking, Nordhoff says. They might also be candidates to receive fibrinogen-reducing drugs, he suggests. A number of medications on the market reduce fibrinogen, although they were not developed to do that specifically, including beta blockers for high blood pressure.
So begin administering fibrinogenlowering drugs? "God, no," says Greg Vercellotti, an associate professor of medicine and hematology at the University of Minnesota and an expert in clotting. Fibrinogen is an acute-phase reactant that increases with inflammation, he says, "so you'd wonder if the patient had a hidden cancer or infection."
Framingham's Kannel acknowledges that no one really knows how elevated fibrinogen levels could cause heart disease, but he suggests possible mechanisms: with more fibrinogen around, it is more likely a clot will form; higher levels also could be a measure of the activity of lesions and the body's efforts to repair them. "The Significance of rising or falling levels of fibrinogen is a continuing saga in research," Kannel notes. ABS would like to write itself into the story. -Deborah Erickson
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SCIENTIFIC AMERICAN June 1991 119 © 1991 SCIENTIFIC AMERICAN, INC