DIY or Survey? Identifying interfering substances

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Souers

Dr. Zimmerman, a member of the CAP Instrumentation Committee, says the Survey overall does “a pretty good job,” though the higher values of lipemia hadn’t been assessed as well as she would have liked.

In the past, the Survey did yield some imprecise evaluations for lipemia for certain assays, Dr. Pearson says, but that is no longer an issue. “It hasn’t been a perfect lipemia product, but the manufacturers we work with have been helping us to resolve these things as they come up. And the CAP staff is constantly looking at the data coming back from these Surveys to make sure we’re really proactive in identifying some of these issues, instead of reactive.”

In Dr. Zimmerman’s laboratory, the Survey is used not only in its intended manner but also off-label, she says. “It’s kind of crude, but you can use the vials and spike them with the analyte of interest and use that too.” She and colleagues used it to help them develop their vitamin D test.

“I hadn’t even thought about using the Survey for that purpose,” Dr. Pearson says, “but it makes sense, because with our Survey material, we reliably know what the concentration of the interferent is in a particular vial, which could enhance the quality of any type of validation study.”

The Survey’s creators and users would like to change a few things about the Survey, mostly pertaining to its scope. “One of its shortcomings is that it’s really only for the chemistries,” Dr. Zimmerman points out. “There’s one immunoassay that’s included, but other immunoassays are not included, and drugs are not included. I guess we could just spike various drugs into the vials we get already, but then we don’t get the graphs and all that.”

Dr. Pearson agrees that laboratories would find it valuable if the Survey were able to identify additional substances. “If we were able to manufacture a product that would let laboratories test for a less prevalent interferent, that would be of huge value,” she says. “We do have ideas for how we can extend this particular Survey to other areas within the lab, such as coagulation. We’re learning that the methodology for many of the automated coagulation tests is susceptible to some of these common interferents, such as hemoglobin. So we would like to eventually be able to widen the net.”
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Anne Ford is a writer in Evanston, Ill.