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Are you a decision making miser? Hopefully not!

I’ve been reading about bias and all the problems that brings to decision making.

You know the sort of thing, you’ve just been to a conference on your favourite topic, let’s say that's atopy (OK, I know that skin cases are not your favourite but they are mine). That’s in your head and in comes Sam the West Highland Terrier, scratching. Could it be atopy? Well, yes it could, it is a Westie after all. But you still need to keep an open mind - it could be fleas. Next is a collie, scratching. Could it be atopy? Not common in the breed, but could it still be in there? What do you do? Treat for fleas or other ectoparasites (it is an outdoor farm collie after all), or think about the new drugs for pruritus? You start looking back through the history, looking for a pattern . Any scratching of the ears or around the eyes? Any seasonal scratching? What are you going to do?

I would hope the answer would be treat it for fleas – they are much more likely in the first instance.

But it does highlight how we can be influenced by events and what’s in our head.

Cognitive miserliness (my term for the year) is where your thinking takes the easiest route. This doesn’t mean that it’s wrong but you could miss out other possibilities for what is wrong with these patients. Think about your list of differentials for an itchy dog – topicals (have they washed it in tea tree oil? Please don’t), parasites (Cheyletiella, scabies), infection (bacterial or fungal), neoplasia (lymphoma) to name a few.

Taking the approach that all itchy dogs are likely to have fleas, is going to be right a lot of the time. But not always. Equally, taking the approach that all itchy westies are atopic will be right some of the time, but not always. So what do you do? Fleas are easy – take a comb. You can do that while you’re talking to the owner. In dogs, you are likely to find flea dirt. In cats, less likely as they groom it off. So a negative flea comb in a cat does not rule out fleas. You can use treatment as an exclusion. Just explain to the owner that the most likely cause is fleas, and that you have to exclude that before you do any more work up. Get them to come back in 7-10 days (unless it’s dramatically worse) and review. Did the flea treatment make a difference?

Similarly cats with bald bellies are most likely to have fleas. They are itchy and overgroom. Feel the hairs that are left – do they feel rough as if they’ve broken off? In that case it’s not an endocrine problem. There are some cats that are stressed or have behavioural problems who can present with a bald ventrum – however fleas are still more common. So rule them out with treatment.

In this way, you’re treating the case and not being a cognitive miser.


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