The agency said its aim is to analyze the way CMS has chosen to implement PAMA and to estimate the potential financial impact to Medicare as a result of those choices.
The diversity of the organizations that have signed the letter to CMS demonstrates widespread concern over this policy.
After a GAO report found that CMS may be overpaying for lab tests, the legislator is asking the government payor to explain how it will ensure appropriate use of taxpayer funds.
CMS's move to restrict coverage could limit test access for early-stage cancer patients and negatively impact lab revenues.
Smaller labs that serve large Medicare populations, such as skilled nursing facility labs, have cut services and expressed concerns about their survival.
The amicus briefs challenge the method in which HHS collected data to establish market-based Medicare prices and found flaws in a district court decision dismissing the case.
HHS Secretary Azar's implementation of PAMA resulted in market-based Medicare prices that don't accurately represent the market, ACLA argues.
ACLA was critical of the report, saying it "fails to reflect market reality" and calling on Congress to intervene to prevent further cuts.
At the Personalized Medicine Conference this week, stakeholders historically at odds over lab test regulation said it is up to Congress to resolve the issue.
Newly announced changes will enable more hospital outreach laboratories to submit lab pricing data, but lab groups say more changes are needed.