WASHINGTON -It's fish or cut bait for direct contracting.   With state insurance regulators seeking direction and trustbusters politically shackled, physicians and moguls are seizing the moment to gut the third-party payer layer. Hundreds of thousands of employees are already covered by health plans that omit an insurer.   On medicine's side, doctors are joining together in physician-sponsored organizations (PSOs) and physician-hospital organizations (PHOs) to seek out contracts directly with employers. On the business end, self-insuring employers are linking to seek direct contracts with doctors and hospitals for an allotted fee.   Yet no one really has an accurate handle on how many physicians, hospitals, or employers are involved. One early 1996 estimate counted 92 contracts between major employers and providers. But the AMA, conceding scant data, found that a whopping 19% of physicians who responded to a survey said they were involved in direct-contracting schemes.   State and federal regulators are confused over what to make of these new middleman-killing entities. The National Association of Insurance Commissioners, alarmed by the unknowns of the pas de deux, issued an alert to members last summer calling for close monitoring of it.   Yet NAIC says it is sure of one thing-that provider networks that accept full capitation are no different than indemnity plans and fall under current insurance laws. But the American Hospital Association and AMA say self-insured employers-not providers-retain the risk in direct contracting. They say self-insured employers act as their own insurance companies, bearing all risk.   Though the obvious motivation for physicians is to nix third-party hassles and recapture some of the HMO booty lost to Wall Street, employers see more than just lower costs.   In Houston, it was employers who sought out direct contracts, in an effort to end-run HMOs perceived as too dictatorial on doctor and hospital choices. In just a few months, nearly all hospitals and doctors had signed the business coalition's direct contracts, leaving HMOs fuming.   On medicine's end of the spectrum, some 350 physicians in Memphis linked to form a doctor-run HMO to negotiate direct contracts with local employers. Dozens of medical societies and other doctor groups nationwide are doing likewise, though a sprinkling have been rejected by federal trustbusters as cartels.   Employers in Minneapolis-St. Paul have formed a direct-contracting organization in an area that's come to be dominated by an HMO trium-virate. Businesses say the Twin Cities' three HMOs, united by merger after merger, had become indistinguishable on price and quality. Direct contractors' raison d'être: virtually all hospitals and doctors had joined all three HMOs, negating competition.   Yet some see a rocky road. "These are going to be difficult times for phy-sicians and hospitals because we are going to see aggressive purchasers making use of their position in an overcapacitated market," says Dr. Gail Wilensky, who chairs the Physician Payment Review Commission.   Moreover, employers and physicians have different motivations, says Kim Barnes of the Richmond (Va.) Area Business Group on Health.   "It's wrong to think that an employer just wants to get around managed care," she says. "Physicians must offer something to employers that managed care can't." She feels that proof of quality and continuity of care will be PSOs' main hurdle.   For regulators, a more immediate concern is whether hastily formed PSOs will fold when trouble arises. In an HMO trade group's survey of the 50 state insurance commissioners last year, most said that they would require a PHO to get an HMO license if it bears full capitated risk. Less clear cut, however, were cases of partial or downstream risk-where the PHO provides services under a capitated deal with a licensed HMO.   But physicians say it's nonsense to think a group practice or a hospital would leave a community en masse. PPRC agrees. "A PSO can credibly promise through its provider contracts not to make beneficiaries liable for the costs of services furnished by the PSO," says PPRC.   It suggests that cash reserves be waived in favor of a contractual requirement that bankrupt doctors and hospitals would continue to care for patients without compensation till patients can join another health plan. But in NAIC's draft model, dollar reserves would be mandatory, based on the amount of fiduciary risk a physician or hospital assumes.   The AMA and others say the proposed NAIC formula may be even more onerous than standards now in place for HMOs and other insurance products. State insurance regulations are designed to regulate financial intermediaries, the AMA says, not health-care-delivery systems.   "We would have hoped for lower standards than this," says AMA attorney Ed Hirshfeld, who points out that HMOs in the 1970s and the Blues in the 1930s were granted softer solvency standards to help them get going. "We need separate solvency standards entirely for PSOs."Insurers and HMOs are pushing for tighter standards as a way to keep PSOs out of the market, Hirshfeld says. Indeed, insurers and HMOs admit their biggest fear is that Congress-now finalizing PSO solvency rules-will set standards in Medicare plans that usurp state laws. With presumably softer financial standards in place, PSOs would soon swamp private markets too. -Joe R. Neel