There have been a lot of stories about dogs that can diagnosis COVID by smell, like this fresh one from the Guardian: Faster than a PCR test: dogs detect Covid in under a second. Study in London used six enthusiastic dogs in a double-blind trial.
It’s an irresistible story, and I didn't resit it. I quipped on Twitter: “Someone has a Labrador laboratory — a lab lab.” 🤣 Also, “enthusiastic dogs” seems redundant. Lazy dogs exist, for sure. But apathetic? Never! That species is defined by enthusiasm.
Anyhoo, my dog digression is making my point: dog stories are fun! Everyone wants to hear about the doggos. And it is genuinely fascinating that they can smell COVID (and cancer, and other pathologies).
But there’s a “but” that we need to sniff here…
Dogs are great and dog diagnostics may be nifty, but it’s also really not reliable and scalable. It’s probably more useful as clickbait than anything else. Science journalist Jonathan Jarry, with a terrific dose of perspective:
How good a dog is at correctly identifying disease when it is there and appropriately not flagging patients when disease is absent (what are called “sensitivity” and “specificity”) varies a lot. In fact, many studies and reviews of studies point out the variation between breeds, within breeds, and between individual dogs… even for dogs similarly trained by the same institution. This variation means a dog is not as reliable as they should be. Then there is the issue of concentration. When testing a single dog which had been trained to sniff out a hospital-acquired infection by C. difficile, the authors of the study noted that their beagle got clearly distracted by “unrelated stimuli” (a life-size gorilla balloon among other things, I am told): in fact, a visit to the paediatric ward was deemed unusable because the children got excited and got the dog sidetracked.
Dogs are all about “unrelated stimuli,” in my experience. Even well-trained ones.
The whole article is much more interesting than the clickbait. Read it all: Barking Up the Wrong Tree: The Trouble with Disease-Sniffing Dogs.