Is Molecular Testing the Holy Grail?
“Go and tell your master,” King Arthur offers a French soldier in Monty Python and the Holy Grail, “that we have been charged by God with a sacred quest. If he will give us food and shelter for the night, he can join us in our quest for the Holy Grail.”
“Well, I'll ask him,” replies the French soldier, “but I don't think he will be very keen. Uh, he's already got one, you see.”
In the laboratory, we are seeking that Holy Grail of a test with 100% specificity and 100% sensitivity, one that gives no false positives or false negatives. Its quest has been a large part of laboratory medicine, from monoclonal antibodies to cardiac troponin to absolute cell counts. The more often our testing correctly identifies disease, the more useful it is to doctors.
Lately, the Grail seems to be molecular testing. Meridian’s Illumigene method, for example, offers an affordable benchtop assay using LAMP (Loop-Mediated Isothermal Amplification) technology to detect toxigenic C. difficile and other organisms. The manufacturer claims 95.2% sensitivity and 95.3% specificity. For smaller laboratories, this kind of technology opens a tantalizing door into a future of cheap, rapid molecular testing.
Theoretically, such molecular testing accurately identifies an organism with faster, better certainty. Similar assays exist for MRSA, another bug from the black lagoon that has been terrorizing hospital patients. But isn’t this stuff everywhere? Imagine sneakered, nose-picking children at visiting hours, and you get the idea. I’m not sure healthcare workers are much cleaner, sometimes.
At a recent meeting a State laboratory microbiologist cautioned against over-interpreting molecular testing. “Is it the be-all and end-all? No,” he said. “It’s another piece of the puzzle for physicians.”
I’ve talked to ED docs about molecular testing, and they always say the same thing. “We treat the patient based on presentation. It’s nice to know the answer, but it probably won’t change what we do.” I wonder how these attitudes will evolve as the technology becomes commonplace in all laboratories.
I suspect it’s too early to tell. In the meantime, we’ll keep looking.
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