Podcast: Screening for thyroid dysfunction in asymptomatic adults
Transcript
Andreas Laupacis: Hi, my name is Andreas Laupacis, I'm the new editor-in-chief for the CMAJ and today we're going to talk about thyroid dysfunction, specifically whether we should screen asymptomatic individuals for thyroid dysfunction. I've been a general internist for many, many years. I must admit that's not something I've been doing, but I gather, it's something that's done not infrequently. So I'm looking forward to talking with Dr. Richard Birtwhistle, who's a family physician in Kingston and a professor in family medicine and public health sciences at Queen's University. About this topic, Richard chaired a group associated with the Canadian Task Force for Preventive Health Care that made recommendations around this topic. So Richard is joining me from Kingston, which is where I went to med school. Richard, welcome.
Richard Birtwhistle: Well, thanks very much. Hello, Andreas.
Andreas Laupacis: Maybe first, do you have a sense of how many people are screened in Canada for thyroid dysfunction or what led you to the taskforce. I'm sure has many topics that you can choose to look at. So what made you think that this was important enough to write a guideline about?
Richard Birtwhistle: Well, I think there was a perception certainly among the family physicians on the task force, that there was TSH or thyroid dysfunction screening, happening fairly commonly in practices. We actually have had a recent study done by the Canadian primary care sentinel surveillance network, Michelle Greiver and colleagues in the UK. It has not been published yet. But they found that somewhere in the neighbourhood of a third of adult patients had had a thyroid test done over two years without any other finding within the lead electronic medical record for an indication for the test. So that's pretty significant that there's you know, that many people who seemingly are having who are asymptomatic and having having thyroid testing done.
Andreas Laupacis: That study was done in the UK, you're saying?
Richard Birtwhistle: Right, it was both Canada and UK. So okay, it was data, the electronic medical record data from the Canadian primary care sentinel surveillance network.
Andreas Laupacis: Maybe you could summarize briefly for us what you have recommended about thyroid screening and how confident you are in that recommendation?
Richard Birtwhistle: Recommendation is pretty straightforward. It was it's the Canadian nonpregnant adults who are asymptomatic, do not need to be screened for thyroid dysfunction, either hypothyroidism or hyperthyroidism. And I think we're quite confident in this recommendation, even though we the evidence was rated as as low quality, we gave it a strong recommendation. And I think part of the low certainty was related to our use of the grade system for assessing evidence, and that there was actually no direct evidence. So there have been no direct screening trials done for assessing benefits of thyroid screening. So all of the evidence we used was indirect, mostly related to both randomized trials and some cohort studies looking at treatment.
Andreas Laupacis: So if I've got you, right, there's no randomized trials, like we have in mammography screening, for example, where a large number of asymptomatic people are randomized to either get screened or not. So that's why you couldn't give it at a high methodological recommendation. But the same time you said there were some randomized trials. So what were those randomized trials of?
Richard Birtwhistle: So we undertook a systematic review, to look for any evidence that screening for thyroid dysfunction resulted in clinical improvement and those who were asymptomatic. And so we we reviewed, or our team at least reviewed 22 studies, 19 of which were randomized controlled trials of treatment, and three cohort studies and this compared treatment versus placebo, or no treatment in patients who are identified with an elevated TSH.
Andreas Laupacis: Okay, so these are people that were identified with an elevated TSH but presumably didn't have a compelling you know, most of the people that I've diagnosed with hypothyroidism, for example, I would sort of say, it'd be unethical not to replace them with T4 because they're clearly symptomatic. So these were, or these people that have what we call subclinical hypothyroidism or hyperthyroidism?
Richard Birtwhistle: It was certainly the ones who were treated, would fall into that category. So the population that were entered into the randomized trial were were patients who were quote screened somehow by the group; they had a TSH done for some reason, that probably wasn't wasn't was not related to symptoms. And so they got into the study of, you know, many of these people have subclinical hypothyroidism as an example. And there have been no trials at all actually looking at hyperthyroidism.
Andreas Laupacis: Okay, so it's all hypothyroidism. And when you looked at the systematic review of those trials, as I understand it, you found no clinically important effect on likelihood of death sort of cardiovascular outcomes, or even I think, sort of measures of well being or quality of life. Am I right about that?
Richard Birtwhistle: That's, yes, that's correct. And, you know, we also looked at other other things such as weight change, mood, cognitive impairment, and some, there were some immediate intermediate outcomes looked at, like blood pressure and blood lipids and to really, you know, overwhelming a did not seem to be treatment effect.
Andreas Laupacis: Okay. So it sounds like you said before, it sounds like a fairly straightforward recommendation, which is don't screen asymptomatic nonpregnant adults. And although there wasn't any randomized trials of screening versus no screening, per se, the evidence is pretty supportive of that recommendation, what would you say to a doc that would sort of say, Well, I don't know how much it is, maybe you can tell us actually how much a TSH costs but that, you know, there's no side effects to doing a TSH and it's not a costly test. So, you know, I think I might continue to screen anyway.
Richard Birtwhistle: I think that's, you know, a common argument used for, I think, doing blood tests. Other examples are PSA for prostate cancer screening. TSH is an inexpensive test. But if it comes back abnormal, that's just the start of the cascade. It comes back abnormal, it may result in further testing, like a thyroid ultrasound, it can certainly result in unnecessary lifelong treatment, regular TSH measurement and regular visits to health professionals who follow up. So not only that, it medicalizes a person without any apparent benefit to them. So while we can say yes, the individual test is is inexpensive, there's a lot of things that can fall out of hat finding an abnormal test that may not result in any lasting benefit for the patient.
Andreas Laupacis: When I find that argument, you know, quite convincing your comment about just you know, medicalizing people and and I presume that quite a few docs, if they got an abnormal TSH back and maybe the T4 isn't all that abnormal might just sort of say, I'm going to follow them, but you're still going to re, you know, redo the test and bring them back and have given them another potential diagnosis that they don't actually have.
Richard Birtwhistle: That's correct.
Andreas Laupacis: So how are you and your colleagues disseminating the guidelines? What should we do to get this out there to docs? And is there anything for patients? Does your guideline group produce patient oriented material? And if you do, how do you get it to them?
Richard Birtwhistle: We do. They're on our website, there's information for patients, there's information for physicians. Obviously, through the CMAJ. We'll be having sort of webinars with a variety of stakeholders once the publication comes out. And so we work with your old group in Toronto, with Li Ka Shing and they help us to produce patient materials and communication materials to distribute widely.
Andreas Laupacis: Great. Richard, is there anything that I haven't asked you about that, that you think our listeners should know about?
Richard Birtwhistle: Just to reinforce something around, if you know, somebody actually does come to see a physician with symptoms suggestive of, of thyroid dysfunction, this guideline does not cover those people. And they're, you know, somebody's coming with significant or unexplained fatigue or weight change, cognitive changes and some cardiovascular palpitation, that sort of thing that that certainly TSH should be part of their investigations. And I think the other thing is that this guideline doesn't cover the sort of people who are on certain medications, such as lithium or amiodarone, who may as part as part of the management have thyroid function testing, patients who've had head and neck radiation, and those who've had pituitary or hypothalamic disease. This is these are people who may well require some, some thyroid dysfunction assessment.
Andreas Laupacis: Okay. Yeah, important qualifiers on who your guideline is applicable to. So thanks for that. Anything else?
Richard Birtwhistle: Just to say that we're, we really are hoping that clinicians who are doing TSH screening as part of their practice will reconsider that practice. And those who aren't will not start, you know, particularly reaching out to family practice residents, people who are in training to understand the role of, of assessing for thyroid dysfunction.
Andreas Laupacis: So, thanks, Richard. So, I've been talking to Richard Birtwhistle, who's a family physician, clinical epidemiologist, and I noticed Richard, you're an emeritus professor. I just became an emeritus something rather too. So we're both together, so that's awesome.
Richard Birtwhistle: It's great.
Andreas Laupacis: Richard chaired the working group for screening for thyroid dysfunction for the Canadian Task Force for Preventive Health Care, and to read the clinical practice guideline, please visit cmaj.ca. Just a little infomercial here, if you haven't yet subscribed to the CMAJ podcast, we'd love it if you did, on SoundCloud, Apple podcasts or any podcast app. If you do, you'll be notified every time that we publish a new podcast episode. And please let us know how we're doing with our podcasts by leaving a rating. I've just started here at the CMAJ. So I'm asking everybody, you know what people think of the various parts of the journal we have. So I'd love to hear from you about that. So I'm Andreas Laupacis, editor-in-chief for the CMAJ and thanks for listening and chat with you soon. Thanks. Bye bye.