Scientists have questioned the ability of dogs to feel the "smell of cancer"

Roman Fishman, N+1

European researchers have again tested the ability of dogs to recognize lung cancer by the smell of patients. Contrary to some previous evidence, the animals have shown themselves to be not very effective in performing this task. Most likely, the fault is not the nose, but the restless disposition, which makes dogs far from the best diagnosticians. Scientists write about this in an article published by the Journal of Breath Research (Hackner et al., Canine scent detection for the diagnosis of lung cancer in a screening-like situation).

Incredibly sensitive sense of smell makes dogs quite effective in recognizing even trace amounts of volatile substances. They are used to search for explosives and drugs, and scientists also know the ability of these animals to detect molecular markers of disease in the breathing of patients with type I diabetes (a few months ago, British biologists showed that dogs react to increased amounts of isoprene associated with hypoglycemia).

At the same time, the "canine diagnosis" of oncological diseases remains a subject of discussion. For example, in 2006 it was shown that they can really learn and recognize lung cancer with sufficient reliability. This was confirmed by the works of 2011. However, a new study conducted by Austrian and German scientists led by Klaus Hackner makes it doubtful that these animals will ever be used in oncology.

Six dogs of breeds with outstanding nose were selected for experiments: golden Retriever, Labrador, German Shepherd, Risenschnauzer, Munsterlander and Hawaiian Bichon. The animals underwent preliminary training for six months, training to recognize the smells of cancer patients. Then the authors used a group of 122 volunteers, of whom 29 were diagnosed with lung cancer (but treatment has not yet begun), and 93 showed no signs of the disease.

In double-blind experiments conducted by Hackner and his colleagues, dogs recognized the smell of patients in 79 percent of cases. However, when sniffing samples obtained from healthy people, dogs performed much worse, demonstrating the correct reaction only in 34 percent of cases. Their effectiveness turned out to be noticeably lower than in previous works.

"Animals should not be considered as strict analytical machines, one hundred percent accuracy with them is never achievable, which is shown for other areas of their application (for example, when searching for explosives and narcotic substances)," the authors conclude. – From the point of view of the dog itself, the smell recognition procedure is something like a game that can bring a reward. (...) At the same time, the dog can change the behavior strategy, focusing on getting less reward and making less effort." Perhaps, for the diagnosis of oncological diseases, it is better to turn to pigeons, which do not have a good nose, but have shown themselves to be excellent diagnosticians, finding even poorly visible traces of a breast tumor on histological images.

Portal "Eternal youth" http://vechnayamolodost.ru  29.09.2016