PALM BEACH, Fla. (AP) _ A state board Wednesday endorsed a study saying ownership of clinical labs by physicians encourages unnecessary tests and higher costs.

The Health Care Cost Containment Board's unanimous vote clears for a possible crackdown on doctor-owned labs. The board rejected criticism by the Florida Medical Association that the study was biased and overlooked contradictory data.

The $150,000 study by Florida State University was commissioned by the Florida Legislature in 1989. It is the nation's most comprehensive examination to date on the effects of such joint ventures, and has been closely watched by Congress and other states.

It found that when doctors make referrals to clinics they own, patients undergo nearly twice as many tests - at double the cost - as at independent facilities.

''Self-referral threatens our modern health care system,'' Robert Carl III, one of the nation's largest operators of diagnostic imaging centers, told the board.

Carl, chief executive officer of Atlanta-based Health Images Inc., urged the board to recommend laws against such referrals, saying that doctors who have invested in such facilities ''see their patients as commodities.''

The study, released Aug. 8, was based on 2,669 questionnaires sent to nine kinds of medical centers owned by doctors, including nursing homes, clinical laboratories, radiation therapy and diagnostic imaging centers. Imaging centers offer X-rays, CAT scans and ultrasound tests and magnetic resonance imaging.

The study found that labs owned by physicians charged an average $43 per patient, compared with $20 per patient charged by other labs.

The study showed that 92 percent of the imaging labs in Florida are owned by doctors and that these labs provide little access to the poor. Fewer than 1 percent of their patients subscribe to Medicaid, the study said.

The approval of the study means that the board's staff can begin developing new regulations to control joint ventures, but doctors are sure to fight any proposal that threatens to become law.

Last month, the Florida Medical Association accused the study's authors of bias and of interjecting editorial remarks while ignoring statistical data that contradicted their conclusions. The association said investment by doctors in labs makes economic sense.