The rate of improper payments in Medicare's purchases of home medical equipment is significantly higher than the government has estimated, according to a federal audit. The report by Inspector General Daniel R. Levinson at the Department of Health and Human Services found an error rate of almost 29% in a sample of claims paid in 2006 under Medicare's durable medical equipment program. The Centers for Medicare and Medicaid Services had estimated a rate of 7.5%. "We attributed these review discrepancies to the . . . contractor's reliance on clinical inference rather than additional medical records available from healthcare providers, CMS's inconsistent policies regarding proof-of-delivery documentation, physicians' lack of understanding of documentation requirements and CMS's lack of procedures for obtaining information on high risk DME [durable medical equipment] items from beneficiaries," Levinson wrote in the report.