Calypte Biomedical Scientist Presents Data On HIV Test Discordancies.

SAN JOSE, Calif.--(BUSINESS WIRE)--April 23, 1999--

Presenting at the Oak Ridge Conference of the American Association for Clinical Chemistry (AACC), Dr. Howard Urnovitz, chief scientific officer of Calypte Biomedical Corporation (NASDAQ: CALY), explained results of a significant clinical study of 826 individuals at high risk for HIV, whose blood and urine were tested for antibodies to HIV-1. The study, which was conducted by Calypte in conjunction with Independent Reference Laboratory, produced 10 individuals with discordant results -- meaning their blood and urine results did not agree. The 31st Annual Oak Ridge conference is Friday and Saturday, April 23 and 24, at The Fairmont Hotel, in San Jose.

In six of these individuals tested, antibodies to HIV-1 could be detected in urine but not in the matched blood sample. These six subjects have been described as urine positive/serum negative, or UPSN. In the remaining four individuals, antibodies could be detected in serum but not in urine. Follow-up testing is planned for all 10 of these individuals, during which time an independent lab will test them to determine if the HIV-1 virus itself, and not just antibodies to HIV-1, can be detected.

Dr. Urnovitz presented this data in the plenary session entitled: "Beyond Blood: The Use of Alternative Body Fluids and Detection Methodologies." During his presentation, Dr. Urnovitz explained that two of the six UPSN subjects in this study had a urine reactive panel with antibodies to all the components of HIV-1, strongly suggesting HIV-1 infection. The six UPSN individuals identified brings the total to 18 persons in four different clinical studies where the urine test showed antibody reactivity to the virus while the blood tests did not. These various studies, conducted over the past six years, continue to suggest that in certain individuals the immune system will produce antibodies to HIV that are detectable in certain bodily fluids but not in others.

A notable example of the variation in immune response was revealed in a recent study published by the journal AIDS (January 1999). This study reported on eight individuals with HIV-1 infection and AIDS who tested positive by nucleic acid testing for HIV-1 virus. Three of the eight individuals were persistently non-reactive by all licensed blood antibody screening tests. The remaining five were weakly reactive by some licensed tests, but non-reactive by other tests. All subjects were HIV-1 negative using blood-based FDA-licensed confirmation tests. "This study, together with the data we have seen in other studies, supports our concern that the immune response to the HIV-1 virus is variable and that combination testing of multiple bodily fluids may yield a higher sensitivity protocol for detecting exposure to HIV-1," Urnovitz stated.

"To date, we have relied primarily on testing for antibodies to HIV in blood to screen for HIV exposure," Dr. Urnovitz continued. "Clinical studies conducted during the past five years have indicated that the highest levels of sensitivity may be obtainable by testing for antibodies in multiple body fluids as well as testing for the virus itself with the new nucleic acid tests such as PCR."

This year's Oak Ridge Conference is titled: "On the Road to Non-invasive Testing, the New Millennium of Minimally Invasive and Non-invasive Technologies in Clinical Settings." The internationally recognized conference is designed to help scientific leaders learn how emerging technologies will revolutionize testing in the clinical laboratory of the next millennium.

Calypte Biomedical Corporation is an Alameda, California-based health care company dedicated to the development and commercialization of urine-based diagnostic products and services for HIV-1, sexually transmitted diseases and other chronic illnesses. Calypte manufactures the only two FDA-licensed HIV-1 antibody tests that can be used on urine samples. These tests include the screening EIA and supplemental Western blot tests.

Urine testing is non-invasive, less costly, does not require sample storage or a trained health care worker for sample collection, and is safer because there are no risks of accidental needle sticks. Also, while urine contains antibodies to HIV, it does not contain the actual virus. The availability of both a urine screening test and a urine supplemental test makes it possible to perform a full diagnostic HIV-1 antibody algorithm without ever drawing blood.

Statements in this press release that are not historical facts are forward-looking statements, including statements regarding market adoption of the HIV-1 urine testing system. Actual results may differ materially from the above forward-looking statements due to a number of important factors, and will depend upon the Company's ability, directly or through third parties, to successfully manufacture and market the HIV-1 urine testing system. Factors which may impact the Company's success are more fully discussed in the company's most recent quarterly report on forms 10-Q and 10-K.