Many patients may be undergoing endoscopy with contaminated instruments, a pair of new studies suggest.

Current guidelines from the U.S. Centers for Disease Control and Prevention and others allow the reuse of flexible endoscopes after cleaning and high-level disinfection (HLD). But the instruments often remain contaminated and may infect the next patient, researchers say.

Cori L. Ofstead, who led one of the studies, said it "shows that current reprocessing methods weren't effective, and endoscopes retained fluid and harbored contamination, including pathogens."

"This study identified problems with reprocessing effectiveness for all types of flexible endoscope, not just the complex gastrointestinal endoscopes with elevators. We believe the risk for patients may be highest for bronchoscopes and urology scopes," said Ofstead, president and CEO of the independent research organization Ofstead & Associates in Saint Paul, Minnesota.

"We were surprised to find that two hospitals accredited by The Joint Commission were skipping so many steps or doing them poorly, but we were even more surprised to find that reprocessing failed about half the time, even in a hospital that had very good practices," she told Reuters Health by email.

As reported in the American Journal of Infection Control, Ofstead and her colleagues evaluated the endoscope reprocessing, drying and storage practices of three multispecialty hospitals.

At each hospital, the researchers sampled fully reprocessed endoscopes that had been stored for over 24 hours, and sent the samples for analysis to microbiology laboratories that were registered with the U.S. Food and Drug Administration and certified by the International Organization for Standardization.

The authors found an indicator of organic contamination in 22 percent of the endoscopes and detected microbial growth in 71 percent of the endoscopes.

The research team also visually examined and photographed retained fluid and other irregularities with a camera and borescopes designed to examine channels and ports, and they used a sterile swab and chemical indicator to test for water.

They found fluid in 22 of 45 endoscopes they examined, and the prevalence of moisture varied significantly by site (from 5 percent to 85 percent). None of the drying methods eliminated all residual fluid or waterborne pathogens.

Reprocessing and drying practices conformed to guidelines at one site and were substandard at the other two; damaged endoscopes were in use at all sites.

Mariah Quick, an epidemiologist and research projects manager at Ofstead & Associates, told Reuters Health by email, "It's critically important to ensure that endoscopes are completely dry before storage. Our statistical analysis found very high concordance between a moisture indicator strip and visual inspections done by time-consuming 'scoping the scope.' This means that reprocessing centers can implement an inexpensive, practical protocol for testing reprocessed endoscopes to ensure that no residual fluid remains inside them."

As recommended by guidelines, "an expert should do periodic audits to confirm proper reprocessing practices. Clinicians should ask to see their reports so they can feel confident that any issues have been resolved," Ofstead urged. "To reduce risk, clinicians should also visually inspect every scope before use to confirm that it's free of damage and debris."

"Ultimately, to reduce patient risk, clinicians should move toward the use of sterilized endoscopes," the authors advise.

In the second study, published in the journal Gut, Dr. Margaret C. Vos of Erasmus MC University Medical Center in Rotterdam, the Netherlands, and colleagues found at least one patient-ready duodenoscope contaminated with detectable microbes in 39 percent of all Dutch centers that perform endoscopic retrograde cholangiopancreatography (ERCP), which is used to diagnose diseases of the pancreas and liver.

Overall, 23 of the 150 duodenoscopes tested were positive for microorganisms with gastrointestinal or oral origin (MGO), indicating that inadequate disinfection left residual organic material on the scopes from previous patients.

"These results suggest that the present reprocessing and process control procedures are not adequate and safe," the researchers conclude.