But industry sources say that in checking around on Capitol Hill, they get no sign the idea has traction and doubt that legislators would reverse course to resurrect a notion they previously rejected. House staff are said to have been looking at the idea, even though the House-passed reform bill contained no such provision.

The lab tax was proposed in the original Senate Finance Committee reform bill, but dropped after drawing swift fire from the clinical lab industry. In its place, however, the update to the lab fee schedule is reduced 1.75 percent from 2011 to 2015, on top of a cut in the update to account for productivity gains.

The lab tax was a $750 million non-deductible annual fee on all clinical lab testing providers allocated by market share (except testing for hospital inpatients and labs with revenues under $500,000). The effective rate is estimated at about 2 percent of revenues.