In a ruling that could give consumers a weapon to fight anticompetitive business practices, a split Supreme Court ruled yesterday that a Virginia woman may sue Blue Shield of Virginia for refusing to pay her psychologist's fees.

The court was divided 5 to 4 in its decision on a case brought by Carol McCready, whose bills for a psychologist's care were turned down routinely by Blue Shield. Blue Shield did reimburse customers for medical bills of psychiatrists, however.

McCready sued Blue Shield, alleging that the insurer had violated a section of the Clayton Antitrust Act by conspiring with psychiatrists to refuse to process bills for psychologists' services. This, in turn, injured McCready because she was unable to be repaid for her bills, she alleged.

In an opinion written by Justice William J. Brennan, the court rejected arguments that, because McCready wasn't directly the target of a conspiracy or related to it such as a psychologist would be, she couldn't sue under the Clayton Act.

"We think it plain that McCready's injury was of a type that Congress sought to redress in providing a private remedy for violation of the antitrust laws," the court said.

"Although McCready was not a competitor of the conspirators, the injury she suffered was inextricably intertwined with the injury the conspirators sought to inflict on psychologists and the psychotherapy market," the court continued. "In light of the conspiracy here alleged, we think that McCready's injury 'flows from that which makes Blue Shield's acts unlawful' . . . and falls squarely within the area of congressional concern."

Section four of the Clayton Act "provides a remedy to any person injured by reason of anything prohibited in the antitrust laws," the court said.

The decision "is certainly not limited to cases against Blue Shield or the health care area," said Timothy Bloomfield, an attorney for McCready. "It does have broad ramifications."

The ruling could be helpful for other consumers or businesses suing corporations when injured indirectly by violations of antitrust laws, Bloomfield said.

Thirty states and the District of Columbia have enacted laws establishing the recognition of psychological services for reimbursement purposes, including Maryland and Virginia, whose law became effective in September 1980.

The majority decision was joined by Justices Byron R. White, Thurgood Marshall, Harry A. Blackmun and Lewis F. Powell. Justice William H. Rehnquist filed a dissent joined by Justice Sandra D. O'Connor and Chief Justice Warren E. Burger. Justice John Paul Stevens filed his own dissent.

McCready's voluntary decision to "spend money for services not covered by her insurance policy would have no greater legal significance than a similar voluntary decision by a person who was not a Blue Shield subscriber," Stevens said in his dissent.