Researchers confirm heparin contaminant

WASHINGTON (Reuters) - Researchers said they had identified a chemical contaminating the blood-thinner heparin from China, confirming U.S. Food and Drug Administration findings that it was oversulfated chondroitin sulfate.

They said they had used a standard analytical method to find the contamination, which had been difficult to pinpoint before, and said it might be used to screen other batches.

The tainted heparin killed at least 81 patients and forced a widespread recall of the commonly used blood-thinner. It also caused a diplomatic squabble between U.S. and Chinese officials.

"Given the nature of this contaminant, traditional screening tests cannot differentiate between affected and unaffected lots," Ram Sasisekharan of the Massachusetts Institute of Technology and colleagues wrote in the journal Nature Biotechnology.

"Our analysis suggests effective screening methods that can be used to determine whether or not heparin lots contain the contaminant reported here."

Many patients in the United States and Europe who got the contaminated heparin suffered immediate allergic reactions, with plummeting blood pressure, swelling of the larynx and other severe symptoms.

The researchers freeze-dried the heparin and used a combination of nuclear magnetic resonance imaging and liquid chromatography-mass spectrometry to analyze its structure.

In addition to a known impurity of heparin called dermatan sulfate, they found that contaminated lots contain a molecule that looks similar to heparin and showed it was almost certainly oversulfated chondroitin sulfate.

Oversulfated chondroitin sulfate is derived from a popular supplement used to treat arthritis, among other things. It can resemble heparin's active ingredient but is much cheaper, leading some experts to suspect it was added deliberately.