(Reuters) – The U.S. Food & Drug Administration said on Wednesday it found inaccuracies in sales data of opioid drug products provided by IQVIA Holdings Inc, a vendor it contracts.

The regulator said IQVIA overestimated past data on prescription opioid fentanyl due to an error in its weight-conversion methods, sending the shares of the company down as much as 10.3 percent to $91.57.

The data showed a more than 20 percent drop in the reported kilogram amount of fentanyl sold in the United States for at least the past five years, compared with what was previously reported, the regulator said.

IQVIA collects data to measure the volume of drugs sold by manufacturers and wholesalers to pharmacies and hospitals.

The FDA uses IQVIA’s drug sales data to assess the scope of prescription opioid use and evaluate trends. It also aids the U.S. Drug Enforcement Administration to estimate future medical need for controlled substances.

FDA Commissioner Scott Gottlieb has asked the company to have a third-party auditor review the quality control measures on IQVIA drug sales data as well as all other products of the company used by the regulator.

The agency also said it will brief members of Congress on IQVIA’s data quality issues and their potential impact on public health.

IQVIA did not immediately respond to requests for comments.

(Reporting by Mrinalini Krothapalli and Anuron Kumar Mitra; Editing by Arun Koyyur)