Ice Pops May Lead to False Positive Fungal Test

(Image credit: Ice Pops via Shutterstock)

A woman tested positive for a serious fungal infection, but wasn't actually infected — instead, her test results stemmed from eating ice pops containing a certain food additive, according to a case report.

The tests said the patient had aspergillosis, a dangerous infection caused by mold, but doctors couldn't find any other symptoms. A CT scan didn't find any trace of the fungus in the patient's body, and blood samples didn't contain the fungus, either.

Mysteriously, the patient continued to test positive over three consecutive days.

The doctors treated the woman with antifungal drugs before realizing that the test for aspergillosis also picks up on a food additive used in ice cream. The patient had been eating three to four flavored ice pops daily.

Although the ice pop connection came as a surprise to the woman's doctors, they knew of other reports of false-positive test results due to food products, said Dr. Nicolas Guigue, a pharmacologist at Saint Louis Hospital in Paris, who wrote about the woman's case in a report published yesterday (July 4) in the New England Journal of Medicine. [Microscopic Worlds Gallery: Fascinating Fungi]

The test for aspergillosis looks for a fiber called galactomannan, which makes up the cell walls in the fungus. The same fiber is used in ice pops and ice cream as a thickener and stabilizer, to make them melt better. (This does not mean that ice pops contained mold.)

"Physicians should be aware of this unusual cause of interaction with the galactomannan test, which can result in unnecessary investigations and treatments," Guigue and colleagues wrote in the report.

Invasive aspergillosis is a life-threatening infection, but usuallystrikes only immune-compromised patients.

The patient was a 42-year-old woman who had just received a bone marrow transplant as a treatment for a condition in which the marrow produces too many blood cells. Patients who undergo organ transplants have compromised immune systems, so they are regularly tested for infections such as aspergillosis, because early detection is critical for successful treatment.

Guigue told LiveScience that he suspects galactomannan crossed from the woman's intestines into her blood, and subsequently showed up on aspergillosis tests that were looking for it in the blood.

When the patient stopped eating the ice pops, her galactomannan levels returned to normal, and she no longer tested positive for fungal infection, according to the report.

The doctors tested 37 flavored ice pops of three brands, and found that they all contained high levels of galactomannan.  

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Bahar Gholipour
Staff Writer
Bahar Gholipour is a staff reporter for Live Science covering neuroscience, odd medical cases and all things health. She holds a Master of Science degree in neuroscience from the École Normale Supérieure (ENS) in Paris, and has done graduate-level work in science journalism at the State University of New York at Stony Brook. She has worked as a research assistant at the Laboratoire de Neurosciences Cognitives at ENS.