DALLAS — Federal prosecutors have charged 13 people in North Texas as part of a sweeping nationwide healthcare fraud crackdown involving billions of dollars in false claims. The crackdown was a coordinated effort that included more than 450 defendants nationwide, U.S. Attorney Ryan Raybould said in a news release. Investigators say the schemes involve more than $6.5 billion in fraudulent claims and, in some cases, led to serious patient harm. In North Texas alone, prosecutors say the cases involve more than $365 million in fraudulent billing, targeting taxpayer-funded programs like Medicare and TRICARE. Authorities also seized more than $35 million...