Recent times have seen dogs/">reports of dogs whose sniffing senses are so sharp they can detect cancer in human breath samples. Now, a study in the Journal of Breath Research on lung cancer detection appears to throw a bit of cold water on that notion.
Austrian and German researchers trained six dog breeds (golden retriever, labrador, giant schnauzer, large Munsterlander, Havanese and German shepherd) for six months, before handing them the task of sniffing breath samples from 122 test volunteers. Twenty-nine of the volunteers had already been diagnosed with lung cancer, while the remainder had no symptoms of the illness.
The topline results? In a press release, the scientists said the dogs correctly identified the subjects who had cancer 78.6% of the time. However, they delivered on the negatives just 34.4% of the time.
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The study was performed double-blind, to keep subjective bias out of the picture, which the researchers suggest may have been a contributing factor to the less-than-stellar success rate.
"Our dogs made mistakes with both positive and negative samples," study co-author Klaus Hackner, from Krems University Hospital in Austria, acknowledged in a statement. "One important reason for the inferior results might be that a true double-blind situation puts a lot of stress on the animals and their handlers."
"Success and regular rewards," he noted, "are important for every kind of sniffer detection work."
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Experience was likely not a factor. Each of the dogs had a serious professional-sniffing background -- whether finding buried bodies or catching the scent of avalanche victims in Austria's mountains. In their training phase, prior to the official testing, the canines worked with 150 samples that mixed cancer-positive breath samples with negative.
"This disparity is not likely to be a detection issue," said Hackner. "Dogs have been shown to have extremely sensitive noses, as proven by their use in tracking, bomb detection, and search-and-rescue."
"However," he said, "in contrast to analytical instruments, dogs are subject to boredom, limited attention span, fatigue, hunger, and external distraction."
The researcher thinks the dogs might be able to improve their detection success rate, given a program designed to reward them more often. But Hackner and his colleagues still think a better goal might be development of an "e-nose" -- an electronic sniffer that offers fast, affordable cancer screening.
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