E-Insight

August 2003

Results Available for Bio-Rad Rapid Test Study

A team of faculty and staff at Colorado State University's Veterinary Diagnostic Laboratories, and the Colorado Division of Wildlife, recently completed the first in-depth field validation and assessment of the Bio-Rad rapid test for chronic wasting disease in deer and elk. Detailed in the July issue of the Journal of Veterinary Diagnostic Investigation, the team analyzed more than 25,000 tissue samples and determined that the Bio-Rad test is an excellent rapid test for screening large numbers of samples to detect CWD in deer and elk populations.

Bio-Rad Laboratories' enzyme-linked immunosorbent assay, or brELISA, is an effective and efficient CWD rapid test procedure for diagnosing brain and lymphoid tissue samples. The rapid brELISA takes five hours to complete compared to the three-to-five days necessary for the previously used immunohistochemistry test, or IHC. Diagnosticians at the Veterinary Diagnostic Laboratory can test 990 tissue samples per day with the rapid test compared to 260 per day with the IHC. Additionally, the new study shows that the rapid test is comparable in accuracy to IHC, considered the "gold standard" of CWD testing.

"IHC is a costly, labor-intensive and time-consuming technique necessitating skilled histology technicians and pathologists to diagnose CWD," said Dr. Barbara Powers, laboratory director. "The rapid brELISA designed for large-volume sample screening is a very effective and practical solution to meet the increased demand for CWD testing and surveillance. It is faster, requires fewer personnel, allows for automation and larger daily volumes of samples, and is less expensive."

The two-phase study was a collaborative effort among Colorado State's Veterinary Diagnostic Laboratories, the Colorado Division of Wildlife, the Colorado Department of Agriculture, and the Colorado Veterinary Medical Association. For the initial validation phase, researchers examined 4,175 samples independently by brELISA and IHC. Overall agreement between the two tests was nearly 100 percent for lymph nodes. Based on these results, the Bio-Rad rapid test to detect CWD in deer and elk was granted a license by the United States Department of Agriculture for use nationwide in November of last year. During the phase two field application, researchers studied the effectiveness of the rapid test on a large scale; an additional 20,875 tissue samples were tested for CWD. For this phase, the IHC test was only used to confirm positive brELISA results. The rapid brELISA proved to be equally as sensitive, specific and reliable in the larger field application as in the validation tests.

Participants in the study from the Diagnostic Laboratory and the Colorado Division of Wildlife were: Charles P. Hibler, Kathi L. Wilson, Terry R. Spraker, Michael W. Miller, Robert R. Zink, Linda L. DeBuse, Elaine Andersen, Darrell Schweitzer, James A. Kennedy, Laurie A. Baeten, John F. Smeltzer, Mo D. Salman, and Barbara E. Powers. If you would like a complete copy of the study (Journal of Veterinary Diagnostic Investigation, 15:311-319 (2003) ), contact Dr. Powers at (970) 297-1281 or e-mail at bep@lamar.colostate.edu.