Medicare spends about $10 billion annually on wheelchairs, oxygen machines and other devices for the elderly and disabled. For years, federal inspectors have documented payment errors that expose the program to fraud and abuse.

A report by the inspector general for the Department of Health and Human Services says that roughly 70 percent of payments reviewed by an outside contractor should not have been approved. But Medicare's own contractor estimated the error rate at less than 10 percent.

The review was not comprehensive and consisted of a sample of 250 payments made in fiscal year 2008.
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