A measure that would have modified how medical malpractice lawsuits are brought to court in Connecticut was defeated by five votes in the House on Thursday, possibly on the strength of testimony from a Republican lawmaker who also practices medicine.

The outcome drew an audible gasp from lawmakers in the chamber, where bills are seldom called unless legislative leaders are sure they have the votes.

The strike-all amendment, which already had passed the Senate on a 32-3 vote, would have made it easier for people to file medical malpractice claims against health care providers. But the amendment died in the House after several hours of debate and a 74-69 vote.

The bill would have allowed patients to use a doctor in a “similar” health care field to provide to the court a written opinion, called a certificate of merit, regarding a doctor’s medical negligence.

“I thought we had the votes,” Rep. Gerald Fox III said after the measure was defeated. He added that it was too soon to know late Thursday whether the House would try to raise the bill again before the session ends May 9.

House Minority Leader Lawrence Cafero, R-Norwalk, said he voted for the amendment, but couldn’t have been prouder of the opposition led by Rep. Prasad Srinivasan, R-Glastonbury, who is a practicing allergist. Cafero believes Dr. Srinivasan’s argument persuaded lawmakers to vote against the measure, which is a rare occurrence these days in the chamber.

“I think it’s sort of neat,” Cafero said.

Dr. Srinivasan said that all he did was inform his colleagues of the impact the legislation would have had on the number of doctors and specialists in Connecticut. He said specialty practices are returning to the state and this bill could easily hinder that growth. He said the bill could easily cause medical professionals to move or retire. He said the current medical malpractice law, passed in 2005, is adequate.

“Your peer judging you has to be in the same specialty,” Srinivasan said.

But proponents of the legislation said the current law is too restrictive for consumers.

The bill was supported by the Connecticut Trial Lawyers Association, but it was opposed by medical organizations and hospitals. The trial lawyers testified in March that the current law sets a higher standard for a certificate of merit than it does for an expert witness who testifies in court. They said a medical expert who is not able to sign a pre-litigation letter would be allowed to testify as an expert in court.

The Yale New Haven Health System testified in March that “the ‘similar healthcare provider’ requirement under current law serves as a gatekeeping function that eliminates frivolous lawsuits.” The Connecticut State Medical Society testified that doctors would flee the state if the legislation was passed.