I’ve blogged about fetal lung maturity (FLM) tests before but this is exciting news!
The Clinical and Laboratory Standards Institute (CLSI) has just published a document that provides guidance to labs that wish to perform the lamellar body count as a test for fetal lung maturity. Disclaimer: I participated in creating this guideline.
So why is this exciting news? Currently, the most widely used FLM test is one made by Abbott Diagnostics called the “TDx Fetal Lung Maturity II” test. It’s popular because it’s commercially available, it can be performed quickly, it’s precise, and it’s an excellent predictor of fetal lung maturity. Abbott is the only in vitro diagnostic company that makes this test and a couple of years ago they announced that they would stop doing so at the end of 2011. Labs that perform this test have been left wondering what test they would replace it with. While the lamellar body count is the most logical option, it’s not a well-known test and there are some issues that have to be considered.
One of the biggest hurdles facing labs that wish to offer the lamellar body count test is the fact that it’s a laboratory developed test. The test is performed on FDA-approved automated blood cell counters but the manufacturers of those cell counters have never sought FDA approval for using them to count lamellar bodies in amniotic fluid. Lack of FDA approval doesn’t mean that the test can’t be performed because FDA doesn’t regulate clinical laboratories. In the U.S., The Centers for Medicare & Medicaid Services regulates lab testing performed on humans through the Clinical Laboratory Improvement Amendments (CLIA). CLIA requires that all clinical tests be validated before they are used but the requirements for a laboratory developed test are more stringent than they are for FDA-approved tests.
Many labs are not accustomed to validating laboratory developed tests because they only perform those that are FDA-approved. After Abbott announced the retirement of their FLM test it became clear that labs would need some sort of guidance if they wanted to offer the lamellar body count tests as a replacement. In 2009 I proposed to CLSI that a guideline document on this topic be created. The proposal was approved and several well-qualified volunteers stepped up to help write it. Writing began at the end of 2010 and the final version was approved by CLSI earlier this month.
The new CLSI guidelines will help educate people about the lamellar body count test and it provides a framework that labs can use to validate the test for clinical use. According to a press release, the guideline 1) describes the use of automated cell counting to perform the lamellar body count test, 2) describes methods to assist in test verification and validation, and 3) describes methods to select an appropriate maturity cutoff.