Updated

A new clinical trial funded by the U.S. government exposes premature infants suffering from anemia to risks without fully informing their parents, advocacy group Public Citizen said on Thursday.

The group, in a letter, asked U.S. Health and Human Services Secretary Kathleen Sebelius to stop recruiting for the trial, which aims to determine the best way to treat anemia in premature infants. It also calls on HHS to notify parents of babies already enrolled in the trial of the potential risks.

The Transfusion of Prematures trial, funded by the National Institutes of Health, randomly assigns half of the infants in the study to receive transfusions at a high hemoglobin level and half at a low hemoglobin level. Hemoglobin are the red blood cells that carry oxygen throughout the body.

Public Citizen said the best available evidence suggests a restrictive transfusion strategy is more likely to cause neurologic injury or other harm to extremely premature infants, and the trial exposes more than 900 infants to the inferior treatment.

But consent forms given to parents do not tell them about prior research on which method may be better, or properly describe the risk of death or disability, the group said.

Officials at NIH said they are reviewing the letter.

HHS did not immediately respond to a request for comment. Investigators at trial locations including the University of Pennsylvania, the University of California at Los Angeles and Stanford University also were not immediately available for comment.

Earlier this year, Public Citizen called for an investigation into an NIH-funded study from 2005 to 2009 that was designed to test the effectiveness of different oxygen levels in the treatment of very premature infants. Public Citizen said that study exposed infants to an increased risk of blindness, brain injury and death, without properly disclosing the information to parents.

"This continued pattern of egregious informed consent deficiencies in NIH-funded trials involving the most vulnerable of human beings is deeply troubling," said Dr. Michael Carome, director of Public Citizen's Health Research Group. "These ethical lapses may represent the tip of the iceberg."

Public Citizen has called for an independent investigation of the U.S. system for review and oversight of government-funded research and a suspension of any other similar studies.