FDA warns LeadCare tests not to be used with venous blood samples

When the U.S. Food and Drug Administration first warned Americans in May 2017 that lead tests manufactured by Magellan Diagnostics may provide inaccurate results for some children and adults in the U.S., the agency made a commitment to continue to aggressively investigate the problem.In response, Becton Dickinson recalled its Vacutainer EDTA Blood Collection Tubes with lavender, tan, pink, and green rubber stoppers. The FDA continues to recommend that Magellan Diagnostics' LeadCare tests not be used with venous blood samples because they may give falsely low results, the agency said in an update to its 2017 warning.

As part of its investigation, the FDA found that "there was a significant chance of false results" when Magellan's tests were used on venous blood stored in certain Becton Dickinson collection tubes. The rubber stoppers in the tubes contain the chemical thiuram, which can release sulfur-containing gases that dissolve in blood and bind to lead particles. This, in turn, interferes with the lead test's ability to assess the amount of lead in the blood.

Because rubber stoppers from other manufacturers may also contain thiuram, the FDA's recommendation against using Magellan lead tests applies to all venous blood samples, regardless of the type of collection tube used. Magellan lead tests may still be used on heel- and fingerstick blood samples.

At the FDA’s request, BD conducted studies to assess the accuracy of Magellan’s LeadCare testing systems when used with blood from the vein (venous) collected into BD tubes. The FDA concluded that the studies performed by BD were robust and showed that there was a significant chance of false results with Magellan’s LeadCare tests when used with whole blood collected from the vein and stored in certain BD tubes. Upon further investigation, BD determined that the affected tubes’ rubber stoppers contain a chemical called thiuram that can release sulfur-containing gases that dissolve into blood samples and bind tightly to lead particles. This chemical reaction makes it difficult for the Magellan lead tests to detect the correct amount of lead in a sample.

Given these findings, the FDA continues to recommend that Magellan lead tests not be used with blood samples taken from the vein. Magellan’s lead test systems can continue to be used with blood samples from a finger or heel stick (capillary blood samples).

BD has determined their venous blood collection tubes that contain thiuram and that could be used with Magellan lead tests include those with green tops (lithium heparin tubes), pink, tan, and lavender tops (EDTA tubes). Because the chemical thiuram may be used to manufacture rubber stoppers by both BD and other blood collection tube manufacturers, the recommendation not to use Magellan lead tests with blood samples taken from the vein applies to all brands of collection tubes used for blood drawn from the vein. The FDA is following up with blood collection tube manufacturers serving the U.S. market to investigate if this issue may impact collection tubes marketed by companies other than BD. The FDA is also continuing to evaluate other factors that may have contributed to inaccurate results observed with Magellan lead tests.

Lead exposure can affect nearly every system in the body, produces no obvious symptoms, and frequently goes unrecognized, potentially leading to serious health issues. Lead poisoning is particularly dangerous to infants and young children. While recommendations for lead screening in adults differ from state to state, all states require children to be screened for lead exposure. Some adults are also at risk for lead exposure, including those who work around products or materials that contain lead.

BD uses thiuram in the manufacturing of green tops (lithium heparin tubes), red tops (serum tubes), grey tops (sodium fluoride tubes), pink, tan and lavender tops (EDTA tubes), black tops (seditainer tubes), light blue/black tops (CPT tubes), and green/red tops (CPT tubes). At the FDA’s request, BD is conducting testing to determine whether clinical laboratory tests other than the Magellan lead tests are affected by the thiuram chemical interference. This evaluation is ongoing. Based on the results of BD’s studies to date and our understanding of the chemical interaction that could cause inaccurate lead test results, the FDA does not believe that there is evidence at this time showing that other tests are impacted by the chemical interference. The FDA also has no evidence at this time that other methods of measuring blood lead, including mass spectrometry or atomic absorption method lead tests, are affected by the thiuram interference.