The Utah group submitted a response of around 50 pages and revised the study protocol to incorporate all of the academy's criticisms, he said.

"CDC at that time had no problem with the scientific validity of the study," Lyon said. "In fact, they permitted us to start examining people."

CDC provided its funding, and "there was no indication of problems," he said.

Points addressed

Mary Bishop Stone, project manager of the study, told the Deseret Morning News that by the end of this grant year it will be 3 1/2 years since that response came from the NAS. "If the study was completely inadequate, why did they fund it for 3 1/2 years?" she asked.

Stephen C. Alder, who handles statistics for the study, said he reviewed the NAS comments. The academy "came up with some very good points. I don't think we took issue with any of the points."

In the group's detailed response, it addressed each of the points.

"There were some interesting aspects," Alder said. One point of criticism involved scientific methods and "our statistical power for the study," he said.

"The interesting point was that (section) was heavily influenced by the CDC."

Lyon said a person from the CDC wrote the section that was most heavily criticized.

"And we finally brought in a world expert as a consultant who basically went through all these statistical power and certainty issues, and we incorporated everything he suggested in our response to the CDC. And they were apparently happy."

Lyon had no indication that the CDC would not accept the procedure until he read Gerberding's letter, he said.

The statistics involved, especially concerning the project's uncertainty aspects, "are very challenging," said Alder. The nature of the uncertainty is that there are aspects relating to radiation exposure that are estimated, but within a range rather than a single value.

Because of that, the study enlisted the help of a world leader in the field, who developed methods and demonstrated that the statistical power in the study was adequate and the statistical methods were sound, Alder said.

Researcher responds

Lyon took sharp exception to Gerberding's comment that the university was "unable to reproduce the dosimetry from earlier work."

Researchers corrected errors that were inherent in the programming of a huge, complex calculation needed to figure dosimetry, he said. "But we are able to reproduce the dosimetry and have actually improved it substantially."