A test widely used to detect tuberculosis may have falsely suggested that thousands of Americans are infected with the disease, a Nader-founded consumer group said yesterday.

The Public Citizen Health Research Group said that faulty batches of the TB skin test may have already led to "unnecessary treatment," both chest X-rays and drugs, "psychological trauma," and "wasting of increasingly scarce public health money."

It accused Reagan administration health agencies of "lawlessness" in failing to recall the product or adequately warn "patients, doctors and hospitals" about potential problems with Aplisol, injected under the skin as a test for tuberculosis.

"The implications of this failure to properly regulate the drug industry are serious, both from a health perspective and from an economic perspective," wrote the group's director, Dr. Sidney Wolfe, in a letter to a congressional oversight committee.

Government officials and Parke-Davis, the product's manufacturer, defended their actions, saying that major screening programs around the country were notified in July and that it was in the "interest of the public" to keep the product available for use, where necessary, rather than removing it from the market entirely.

"There was a problem of a potential shortage of replacement supplies if we recalled that product," said a Food and Drug Administration spokesman, since the Parke-Davis product has 80 percent of the market and there is a start-up time involved in producing new material. FDA officials said that a general mailing to doctors and other health personnel around the country about the Parke-Davis test was expected soon.

The company said that the "negative" results that show up in most people being screened for tuberculosis are still considered "extremely reliable." The problem appears to be with "false positives"--test results indicating that a person may have had past or present infection with the tuberculosis organism and need follow-up tests and treatment.

Generally, those that have a positive skin test will follow it up with a chest X-ray. If the X-ray shows no signs of the disease, some people, particularly those under 35, may still be given preventative doses of a powerful drug called isoniazid.

A memo released by Wolfe from the federal Centers for Disease Control said that earlier this year the government began to receive "unexpectedly high numbers" of positive skin test reactions. In a July mailing to tuberculosis control officers for states and major cities, CDC officials said it would be "prudent" not to use current batches of Aplisol until new batches are available or to switch to a product made by a Canadian company.

A Parke-Davis spokesman said that the company had stopped production and distribution of the material under question and was awaiting approval for a new master batch.

The dimensions of the problem were uncertain, with CDC and FDA officials saying that tests had shown that overall, the reliability of the Parke-Davis TB skin test was "reasonably high" but that in the small group found to be positive, the reliability varied widely in different lots.

The consumer group charged that there were possibly "millions of doses of the defective" product available and "thousands" of people who were affected. It argued that the earlier government notice was not effective in reaching local health agencies, citing the case of Montgomery County.

According to Wolfe, the county noticed an increase in positive skin tests earlier this year but did not learn until late August (from the state and not the federal government) about the potential problem. He said one survey there suggested that about two-thirds of those people with a positive skin test for TB had a negative result when they were retested with a different product.

Wolfe said that as many as 1,000 patients there may have to be retested.