The People for the Ethical Treatment for Animals suggested that pets that have disappeared and are feared dead may well have ended up in local animal research laboratories {letters, June 2}. It is important to examine the facts and evaluate whether that is a valid concern or just a scare tactic that PETA is using to impugn the use of animals in research.

In 1987 the American Humane Society estimated that between 6.3 million and 10.4 million unclaimed dogs were euthanized nationwide. This represents 60 percent of the dogs brought to shelters; most of the other 40 percent are claimed by new or old owners. Some of the pets that are claimed are indeed purchased for use in biomedical research, but that number is small.

In 1988, for example, the U.S. Department of Agriculture reported that only 140,000 dogs were used for all biomedical research. Of these, somewhere between one-third and one-half were bred exclusively for that purpose. This means that about 100 unclaimed dogs (i.e., random source) are killed each year by shelters for each random-source dog used in research.

These numbers suggest that the likelihood of any lost pet ending up in a lab is quite small compared to the chances of it being killed on the roads, reclaimed or euthanized. In addition, because most local labs obtain their animals from out-of-state sources, there is little chance that an owner will find a missing pet at an area lab. PETA is sending people on a wild goose chase when it suggests that they look there.

Obviously, concerned pet owners must protect their animals by making them wear collars and tags and must contact area shelters if their pet disappears. But they also can go a step farther and have their pets tattooed and their numbers entered in a national pet registry program. Lost animals then can be identified and owners contacted even if collar and tags are lost.

Given all this, one must ask why PETA tries to scare pet owners who may have lost a valued animal. If PETA is really concerned with the well-being of animals, as opposed to maligning biomedical research, why didn't it use its letter to describe what people could do to protect their pets?

DAVID P. FRIEDMAN Bethseda The writer is a scientist working for the U.S. Public Health Service.