Amedisys Inc. has issued a letter to its shareholders defending its home health care practices that have fallen under federal investigation.

In the 21-page letter, released after financial markets closed Thursday, Amedisys challenged questions raised by The Wall Street Journal, which examined Amedisys and three other home health providers.

The Journal analyzed Medicare data and reported that Amedisys and other providers appeared to boost the number of visits they made to patients to 10 or above — the threshold at which Medicare reimburses providers an additional $2,200. As a result, the Senate Finance Committee launched an investigation.

Amedisys, LHC Group Inc., Almost Family Inc. and Gentiva Health Services, in federal securities filings, have reported received formal notice of investigations and subpoenas for documents from the Securities and Exchange Commission. All have said they are cooperating.

In its letter, Amedisys said all care is prescribed by the doctors and its physician consultants are not compensated for referrals. In 2009, physician consultants received an average of about $2,600 for the year, Amedisys said.

The letter also said the Journal appeared to assume — inaccurately — a static patient base in 2007 and 2008 when it analyzed visits and payments.

"The key factors impacting our shifting patient population include the trend that Amedisys has been taking care of patients who are increasingly sicker and debilitated and therefore who need more therapy visits," the letter said. "At the same time, other factors have resulted in Amedisys also taking care of more lower acuity patients who require relatively fewer visits."

Amedisys also said it exceeded the national average by 7.1 percent in providing visits not compensated by Medicare. Over 2008 and 2009, those visits totaled more than $95 million, the company said.

"We stand by the integrity of our company and employees," the letter said. "We believe the WSJ article is based upon an inaccurate understanding of a very complex industry and the ever-changing population that we serve, and that it overlooked some important facts."

Since May 13, when the Senate committee letter was sent to the companies requesting information, Amedisys shares have fallen by roughly half to a Thursday close of $26.76.