Lab Screens Serum Samples for ‘Footprints’ of Virus : Valley Firm Tests Military Recruits for AIDS Exposure

Every week, the fate of hundreds of military recruits from across the country is written on strips of treated paper floating in gently rocking trays of amber blood serum incubating in a laboratory in Newbury Park.

The laboratory performs the “Western blot” test, the best available measure of whether a person has been exposed to the virus that causes the deadly disease AIDS.

The serum samples tested come from Army, Navy or Air Force applicants who have already twice tested positive for AIDS exposure on a simpler, less reliable test that the military has required of all applicants since October.

On a typical day, a distinctive pattern of dark bands, similar to the bar codes on grocery items, will appear on at least half a dozen strips. Each such result means that, somewhere in the country, someone will be rejected for military service, be advised to see a physician and then be accompanied home by a recruiter--the last step, to avert suicide attempts.

The Newbury Park facility, the name of which is Reference Laboratory, is run by Damon Clinical Laboratories, a division of Massachusetts-based Damon Corp. Damon last fall won contracts worth $3 million to do the AIDS tests for the military and was recently awarded $10 million in new contracts by the Army--which oversees AIDS testing for all the armed services--to continue the testing for three years.

A positive result on the Western blot guarantees that even if the test subject never develops AIDS--and a majority may not, according to AIDS researchers--he or she will never serve in the military.

It also means that the person was at some time exposed to a dreaded, fast-spreading disease about which little is known.

‘Gold Standard for Exposure’

“The Western blot is as close as we have to a gold standard for AIDS exposure,” said Tim Dondero, a medical epidemiologist in the AIDS program at the federal Centers for Disease Control in Atlanta. The test is about 95% accurate, he said.

AIDS, acquired immune deficiency syndrome, attacks the immune system, leaving victims vulnerable to a variety of deadly infections and cancers. The AIDS virus, called HTLV-III in the United States, is most commonly transmitted through homosexual contact and unsterilized syringes used by intravenous drug abusers.

Dr. William Mayer, assistant secretary of defense for health affairs, has called the screening a necessary precaution until more is known about the ways AIDS can spread.

A blood sample is taken during an applicant’s physical and spun on a centrifuge to separate the liquid part, the serum, from the blood cells. The serum is flown to a Damon laboratory on the outskirts of Dallas where a preliminary screening test, called the HTLV-III Elisa, is run.

The Dallas facility screens at least 70,000 serum samples a month from the military, a company spokeswoman said.

The Elisa test is highly automated and generally costs less than $10 a test but it also produces a high number of false positives, in which tests of the same person later show no exposure to the AIDS virus, a military spokesman said.

Even if a serum sample tests positive for AIDS exposure twice using the Elisa screen, the result is not considered conclusive. At that point, the sample is sent to Newbury Park.

Neither the military nor Damon Corp. will say how many serum samples are sent on for the Western blot. But Howard I. Kim, who designed and directs the testing in Newbury Park, said the laboratory runs from 50 to 300 Western blots each day, six days a week, and that most of them are for the military.

The laboratory, which has about 450 employees, also runs the AIDS test for area clinics and hospitals, Kim said.

The military contracts were “very important,” technical director Robert Foery said. “A $10-million contract is a substantial contract. The thing that’s really good about it is they are guaranteed dollars. You can plan your budget around that.”

The Western blot works by detecting the response of a person’s immune system to the presence of the AIDS virus. Small strips of paper are coated with proteins isolated from the virus, and each strip is soaked in serum taken from the person being tested.

If that person has ever been exposed to the AIDS virus, antibodies circulating in his or her blood will leave the serum and latch onto the proteins on the paper, a process assisted by the gentle shaking.

Several steps and a number of chemical processes later--in a process resembling the production of a photographic print--the presence of antibodies on the paper can easily be seen as the bands.

Typical Test

On a typical test run at Reference Laboratory, after 30 minutes of shaking and heating, most of the 25 paper strips in each plastic tray remain pure white--meaning a negative test. In those cases, the earlier finding was a false alarm.

There are no names on the test slips, only coded numbers representing the recruits.

Shuffled in among the others, 10% of the samples are controls to assess the laboratory’s accuracy, Kim said.

It takes about 12 hours to run one batch of tests, Kim said. The cost of the complex procedure varies with volume. Julian Barber, special assistant to Assistant Secretary of Defense Mayer, said that the military has paid as much as $300 a test and that the current contract breaks down to about $100 a test.

Kim said he assesses every test strip as positive or negative, signs off on sheets containing 25 strips, and sends the results to the Army. He emphasized that the Western blot only picks up the “footprints” of the AIDS virus, that it does not determine whether the live virus is still active in a person’s bloodstream.

He said any judgments on the basis of the test are left to the lab’s customer, in this case the military. “We have tunnel vision on this when it comes to positive results and their implications,” he said.