Doctors performing a heart-lung test that can cause fatal complications should receive specialized training and certification, according to researchers who found that many doctors have a poor grasp of the procedure.

A written exam about the procedure was given to 496 physicians at 13 U.S. and Canadian hospitals. It found that 47 percent were unable to derive "even the most basic information" from the data generated by the test, researchers reported in Wednesday's Journal of the American Medical Association.The study did not record any attempt to give the exam to doctors known to have used the heart-lung test. Rather, researchers gave the exam at random to doctors in hospital departments that use the tests the most.

The test, called pulmonary artery catheterization or PAC, is performed an estimated 2 million times a year and can provide life-saving information if used by a doctor with adequate training. But it can cause fatal complications or lead to treatment errors if used without adequate knowledge, the researchers said.

No training standards exist for doctors learning to use the test and no special credentials are required, they said.

Dr. Roger C. Bone, chairman of internal medicine at Rush Medical College in Chicago, said Tuesday that a moratorium on the use of the test "would be going off the deep end."

Bone said in a telephone interview Tuesday that the rate of serious complications overall is probably 2 percent to 3 percent. And the rate of life-threatening complications less than 1 percent.

"The PAC is very important, very helpful," he said. "It can give us information that may allow interventions that will be life-saving."

He agreed with the researchers that doctors should have to earn credentials to use the test. Bone serves on the American Board of Internal Medicine and the Critical Care Board, which set standards to certify doctors qualified for those specialties.

Bone said the ABIM and the Joint Commission on Accreditation of Healthcare Organizations, which sets quality standards for hospitals, are evaluating the findings.