Measuring a biological chemical called hyaluronan found naturally in joints and the fluid that lubricates cartilage might enable doctors to diagnose osteoarthritis of the knee and hip earlier or more accurately, a new study concludes. Improving diagnosis of the painful inflammatory disorder should become increasingly important as baby boomer age, doctors say.
The research, conducted at the University of North Carolina at Chapel Hill and in Johnston County, N.C., revealed that levels of the chemical, also known as HA, in blood samples corresponded with how advanced osteoarthritis was in a group of rural patients, both blacks and whites.
"Our study shows statistically significant differences in average levels of serum hyaluronan (HA) between individuals with osteoarthritis of the knee as shown on X rays and those without knee or hip osteoarthritis," said study director Dr. Joanne M. Jordan. "Serum HA levels not only were associated with the presence of osteoarthritis but also showed a trend of increasing values as severity of the disease increased."
Jordan is associate professor of medicine and orthopaedics at the UNC School of Medicine. Also associate director of the Thurston Arthritis Research Center, she is principal investigator for the long-term Johnston County Osteoarthritis Project. That investigation is the largest of its kind ever done and involves more than 3,000 volunteers whose health and experiences with arthritis doctors follow and analyze.
A report on the findings appears in the January issue of Arthritis & Rheumatism, a journal published by the American College of Rheumatology.
Besides Jordan, UNC schools of medicine and public health authors are Dr. Alan L. Elliott, a rheumatology fellow; Dr. Jordan Renner, professor of radiology and allied health sciences; and Anca D. Dragomir and Gheorghe Luta, doctoral students in epidemiology and biostatistics, respectively.
Dr. Virginia B. Kraus, associate professor of medicine, and Thomas Stabler, both at Duke University, Dr. Charles D. Helmick of the Centers for Disease Control and Prevention and Dr. Marc C. Hochberg of the University of Maryland also participated in the study.
Hyaluronan is produced by cells of what is called the extracellular matrix, Jordan said. It is thought to contribute to lubricating joints, a process without which walking and running would be unbearably painful. Earlier work suggested HA might serve as a sign, or biomarker, of osteoarthritis.
"Our study is unique in that it consisted of a large, ethically diverse, population-based sample of African Americans and Caucasians and incorporates five definitions of osteoarthritis as shown on X rays," she said. "This was the first study of hyaluronan and osteoarthritis to include African Americans and to consider how other health problems commonly occurring with osteoarthritis might confound the relationship between serum HA and osteoarthritis."
The researchers studied 753 subjects, including 455 with osteoarthritis in their knees. Volunteers ranged in age from about 51 to 72 and averaged almost 62. About 39 percent suffered from high blood pressure, the most common other illness. The least common was cancer.