The new medFICO score, being designed with the help of credit industry giant Fair Isaac Corp., could debut as early as this summer in some hospitals.

Healthcare Analytics, a Waltham, Mass., health technology firm, is developing the score. It is backed by funding from Fair Isaac, of Minneapolis; Dallas-based Tenet Healthcare Corp.; and venture capital firm North Bridge Venture Partners, also based in Waltham. Each kicked in $10 million for the project.

The score is already raising questions from consumer advocacy groups that fear it will be checked before patients are treated. People with low medical credit scores could receive lower-quality care than those with a healthy medFICO, they argue.

''How much assurance do I have that they're not going to look at this medFICO first, before they decide whether to treat or not?'' asked Linda Foley, founder of the Identity Theft Resource Center in San Diego.

That will not happen, says Stephen Farber, chairman and chief executive of Healthcare Analytics. Hospitals will check the score, which will be based on the patient's medical bill payment history, only after the patient is discharged, he said.

''We only come into play once the patient has been treated and discharged, and the bill already exists,'' said Farber, who has visited hospital executives nationwide over the last six months to sell the concept. ''We just help figure out what sort of relief a hospital should grant the patient.''

Hospitals and other caregivers already can tap into regular credit scores - even without the patient's permission - but those are not necessarily a good indication of whether a patient will pay a medical bill, Farber says. Such credit scores are based on voluntary purchases, such as a car. Health care debt is largely involuntary.

Under the Fair Credit Reporting Act, hospitals and doctors are allowed to report health care debts to credit reporting agencies, but they cannot indicate what they were for.

''They have to do it in a way that there will be no way a person looking at the information would be able to guess what they were treated for,'' said Frank Dorman, spokesman for the U.S. Fair Trade Commission.

Tenet, the nation's third-largest hospital system, with 63 hospitals and medical centers, had $433 million in bad debt through this year's third quarter.