DURHAM, N.C. — Lawyers for patients caught up in a medical mix-up at two Duke University Health System hospitals say patients exposed to used hydraulic fluid are at a higher risk than Duke Health experts want to admit.

The exposure to approximately 3,800 patients was the result of surgical tools mistakenly washed in used hydraulic fluid during the cleaning process.

"Our findings are more comprehensive," said Dr. Annette Santamaria, a toxicologist hired by lawyers representing patients in this case. "We detected more metals than was reported by Duke."

Lawyers partnering with Raleigh law firm Henson Fuerst, which is representing close to 500 clients in the case, said Duke Health's assessment that the fluid was not harmful to patients is premature and misleading.

"It is certainly premature for Duke to make a broad statement that there are no implications resulting from this," said environmental attorney David Weinstein. "There is simply not enough information to draw that conclusion reasonably at this point. I think it is irresponsible to do so."

Santamaria said her analysis shows several different contaminants including arsenic and lead.

Duke Health officials say they have not seen the lawyers' reports, so they cannot speculate on the results. However, they stand by the analysis from RTI International that shows the exposure to used hydraulic fluid was miniscule.

In a written statement, Duke Health said that the residual amount left on the tools was less than a fraction of a drop and that the risk of infection was low and the tools were still sterile. Officials admit, however, that long-term effects of exposure are unknown.

The difference in analysis comes down to how the two studies were conducted.

The Duke Health study looked at the risk from the amount left on surgical tools. The lawyers' study looks at the entire contents of a larger sample.

"We have a better handle on what could've been on the various instruments," Santamaria said.

Conflicting scientific data can make for complicated court cases.

"Expert cases of a scientific nature like this are difficult and challenging," said attorney Jim Gale.

While Gale said he could not comment on the case, he said as a litigator, he has seen cases like it. He said if conflicting reports are allowed in court, the jury will side with the case that is easiest to understand and the most credible.

"While sympathy is a factor, it's not the controlling factor," Gale said. "In a well tried case, the jury will come back with the right answer based on the evidence, not sympathy."

Duke is tracking patient health concerns and has devoted a Web site to providing information.

No one has filed a lawsuit against Duke Health in the case, but there are lawsuits against the detergent supplier, Cardinal Health, and the elevator repair company, Automatic Elevator Co., blamed in the mix-up.

For two months late last year, surgeons at Duke Health Raleigh Hospital and Durham Regional Hospital unknowingly used instruments that had been washed with hydraulic fluid instead of soap. The error happened after elevator workers drained hydraulic fluid into empty soap containers without changing the labels.

The used hydraulic fluid originally came from an elevator repair job at Duke Health Raleigh Hospital.