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Withings Thermo Smart Thermometer Review – A Medical Perspective

The Withings Thermo, a smart thermometer, has been released just in time for the cold and flu season in the UK. I’ve been testing it out to see how their temporal artery scanning tech, compares with my NHS issue Braun ThermoScan in-ear thermometer. So have I a got a new toy in the doctor’s bag, or should Withings go back to the drawing board?

Withings Thermo Smart Thermometer – A Medical Perspective – TitaniumGeek

Withings Thermo

Withings is building itself up to be a whole body monitoring company, looking at everything from sleep, cardiac health (ish) to weight. Following their acquisition by Nokia, they are expanding on that idea to monitoring of the unwell person with the Withings Thermo. A temporal thermometer using a HotSpot sensor enabling you to monitor a person’s temperatures by scanning across their forehead when things are not looking as rosy

I say monitoring another person’s temperature rather than your own, as being a temporal scanning thermometer, there is a bit of a knack to using the Withings Thermo. With an in-ear thermometer, it’s essentially just a case of pushing the probe into the hole and wait for the beep. However, with a temporal scanning thermometer, you need to follow a smooth arc around the forehead. Doing so on someone else isn’t that difficult, but monitoring your own temperature with the Thermo isn’t that easy – a mirror is definitely needed!

Withings Thermo

So mirrors aside, let’s take a look at the Withings Thermo

Device Design

 Withings Thermo

The Withings Thermo looks nothing like any other thermometer I’ve seen. It almost looks a little too friendly to be a medical device. It seems like some of the bright design from the Nokia of the past is leaching into Withings, and to my mind, that’s not a bad thing

The green rubber cap serves both to keep the sensor clean when in transit, but also to stand the unit up when not in use (trust me, I’ve enough cluttering up my doctor’s desk, anything which reduces it’s own office space requirement has already one a point from me!)

 Withings Thermo

At the green, business end of the Thermo is the HotSpot sensor. We have the rubber cover, and a green rubber ending around the top of the unit, with the sensor recessed underneath. But I wonder what would happen if you did get something on it? How well would it work after cleaning?

 Withings Thermo

On one side of the unit is the measuring button and the flat piece of plastic which also has the screen behind it

 Withings Thermo

NO USB power here, on the other side of the unit is the battery cover, with two AAA’s nestled inside.

 Withings Thermo

Interestingly enough there is also a small magnet on the back of the cover

 Withings Thermo

Which makes getting access to the batteries with a finger nail very easy

 Withings Thermo

Before we get onto what it  is like using the Withings Thermo, it’s very important we look at a little bit of the theory of measuring temperature

What is a NORMAL temperature?

If you ask many people, even medics, the answer will be 36.0 – 37.5 degrees C. However, the slightly anally retentive medic, or me (!), will ask first where you are measuring that temp? As the normal temp with an ear thermometer, for example, has a wider range of normal, 35.8 – 38.0 deg C

Withings Thermo

SO what do you do about this big range? One line I use with patients who have a temperature of 37.3 – 37.5 using an in-ear thermometer, is: “You are a little warm – but not hot. However, we’ll still pay attention to that.” Whereas, at 37.5-38.0, they are “Are little hot, but not so that we’ll worry at the moment” basically covering this grey area

In all cases, I’m not going to diagnose a patient as having a fever until they cross the 38.1 boundaries, but then I’ll certainly pay close attention

At the other end of the scale, higher temperatures become even more worrying, and we’re likely going to be discussing getting a review at the hospital if things worsen

Does it matter where you measure?

I think before we go any further it might be worthwhile looking at what a “temporal scanning thermometer” is, and how it differs from other thermometers on the market.

So what makes this type of thermometer so special? How is it better than the classical mercury thermometers that would just be stuck under the tongue “in days of yore”? – Well, for one thing, you’ve not got the increased chance of mercury poisoning if a child decides to bite into either a temporal scanning, or in-ear thermometer, but that also stands for many thermometers today!

Withings Thermo

The Thermo uses 16 infrared sensors in the HotSpot sensor which are scanned across the forehead to take the temperature derived from the temporal artery. This location is used as the temporal artery is supposed to be the next most “real” temperature when compared to using an invasive method of measurement

In fact, Withings put together a very nice little illustration of how to use a temporal scanning thermometer, starting in the centre of the head, and moving until the unit detects the increased infrared radiation from the artery under the skin

There are many different places to measure the bodies temperature, but from a medical perspective, we’re interested in is what a bodies CORE temperature is.

So with that in mind, let’s look at the accuracy i.e. how true a temperature is when it’s taken in different parts of the body:

  • Mouth
  • Rectally
  • In the armpit
  • Tympanically
  • Temporally

There are other locations that temp can be checked, but they are not going to be routine locations and not something a normal person would measure at home, we’re talking things like direct monitoring occurring in ITU.

So a distinction is needed to be made between core body temperature, i.e., The temp to which you are inside and at which your bodies chemical reactions will be taking place compared with the surface temperature you are measuring

As a result, most ideal measurement points are at locations close to major blood vessels: hence mouth, rectum, under-arm and the forehead

So let’s look at those in order – Paediatrics in Child health has an excellent overview of thermometers in children, from which this section is derived:

  • Mouth – a thermometer here needs to go as far back under the left and right side of the tongue as possible. –  IDEALLY not have eaten or drunk for 30mins, and of note is not considered to be accurate when is used to measure the temps of under 5yrs – as it must remain under the tongue, with the mouth closed for 3-4 mins – Have you SEEN how much children <5yrs squirm?!!!
  • Rectum – yes we had to go there, as this is about as close to core temperature as your going to get without physically going inside the tissues of the body (Remember we’re just walking tubes, so going “inside” via the rectum isn’t truly inside. Although if you were on the receiving end of the thermometer, I’m not sure that infrared distinction would matter much to you!! However, apart from the slightly intrusive nature of a rectal thermometer, it is also ~ 0.5 of a degree higher than an oral temperature, and closer to the true body temperature. However, this temperature is slow to change, which may allow an acute fever to be missed
  • Armpit (axillary) – unlike the oral temperature, a temperature measured at the armpit is suitable for all age groups but tends to be considered quite inaccurate given that the thermometer must be applied for at least 5 minutes
  • Tympanic, or ear measured temperature – today this may be the method of temperature measurement that most people are familiar with going to see the doctor, a reading is obtained in approximately 1 second with current tympanic thermometers. But the temperature is not actually measured “in the ear canal”, but in fact, it is the infra-red light bouncing off the ear drum which is measured. This can be a source of error, potentially up to a whole degree. E.g.,  if someone has “tortuous” or winding ear canals, so we may not be able to see the ear drum without discomfort, or if dealing with a child under 2. You see that the probe has a width of 8mm normally, in which case it can’t reliably get into the ear canal of a child under 2 years (Ear canal is 4mm at birth, 5mm at 2 yrs) without discomfort – so a child or baby who doesn’t want something pushed into their ear is going to be even less cooperative, likely affecting the readings further. In both cases, or a squirming child or a tortuous ear canal, if that patient as a reading of 37.5, we could be missing a more significant temperature
  • Forehead temperature  (Withings Thermo) – here the temperature is derived from an infra red recording from the temporal artery at the side of the temple, a nicely accessible major blood vessel. In this case, as the thermometer is measured off exposed skin, a calculation is needed of the surrounding air, to allow for an adjustment of the measured reading to improve accuracy. Taking 2-3 seconds to swipe across the forehead tends to be tolerated more effectively, in my clinical experience, than other methods

Using the Withings Thermo

Withings Thermo

The Withings Thermo is a smart device, thus it talks to your phone. Thankfully this is not an absolute requirement. You can still run it around someone’s forehead and get a temperature with the device.

When the Thermo is scanning for a temperature, as you hold down the side button, you get a slight vibration, and a moving series of dots on the screen, when the temperature has been recorded, the screen will also display a coloured light, green, amber or red, to indicate concern level

The Withings Termo app, is a stand-alone app, as opposed to Withings Healthmate, which I was a little surprised about. It is available on iOS and Android

Withings Thermo

Once installed, the Thermo quickly pairs over BlueTooth is ready to record. Of note that Thermo app can also output data to Apple’s HealthKit and Googles offering

Withings Thermo

If you have set up the app, it allows you to keep a record of the temperatures, which in turn can be useful when discussing the problem with your doctor. The last measurement will tell you the trend so far

Withings Thermo

From a medical perspective, the app encourages you to give you a little more detail, which can be inputted when you click on a particular temperature reading.

There is also the option to take a photo in the app, and record symptoms and current medications. From a medics perspective, these little options are great, as frequently rashes disappear, and symptoms get forgotten, but if they are written down and photographed, it is extra detail for me to work with

Withings Thermo

OK here comes the science – Part 2!

Which might not be a great thing to be compared with, especially when it comes to accuracy of temporal thermometers. As of 2011, at least one well-powered study has scanning thermometers demonstrating an accuracy of 68% (Sensitivity being the ability to detect a true reading, suggesting that more than 1 in 3 children would have been measured as NOT having a temperature when actually they did!)

But there have been a lot of changes to technology since 2011. Unfortunately, a 2015 paper had an even more damning conclusionPeripheral thermometers do not have clinically acceptable accuracy and should not be used when accurate measurement of body temperature will influence clinical decisions“, OR SO IT SEEMED! 

Here is a major problem with medical devices and journal articles, it is often not difficult to massage wording to reach the conclusion you want – I refer you to Withings picture above. In the case of the 2015 article, they are not speaking specifically about temporal scanning thermometers, but ALL peripheral thermometers. Which is a statement that also includes the Braun ThermoScan, used across the NHS!

Withings Thermo

Then this year, the BMJ had a crack at this is the issue, looking specifically at temporal scanning thermometers, using a scientific approach called a Systematic Review – so here we’re getting into REAL stats and research areas. The point being, this is the top of the research pyramid. THE gold standard

Withings Thermo

What did they find? “Temporal scanning thermometers could replace tympanic thermometers with the caveat that both methods are inaccurate.” 

TO clarify that point, they are both inaccurate from an ITU, clinically vital perspective, but for use at home, and in the GP’s bag as an indication of patients approximate condition, they are ok.

SO heavy science out of the way, what did I find?

As mentioned previously, in-ear thermometers don’t play nicely with children, or should that be that children don’t place nicely with them. While in practice, with Withings Thermo, has made my life easier taking temperatures, patients obviously don’t want photos of their child, at the GP surgery, looking unwell on the net.

Given my best friend has recently had a child, well his wife anyway, I had the perfect tester and photographic subject!

Withings Thermo

NO not him – the baby!!! Although my friend is also a GP, so was actually happy to help with the review.

SO we grabbed an Exergen temporal scanning thermometer, the Withings Thermo, and my trusty Braun in ear thermometer and set to it

 Withings Thermo

Here is the real benefit for a doctor or a parent a temporal scanning thermometer, the child really isn’t affected by the temperature being taken, you can literally do it whilst they are sleeping. Starting in the centre of the forehead, and drawing slowly towards the hair line. It’s important that the sweep takes about three secs in order to allow enough data, and not hit the hair line too quickly. I have found myself repeating a result, as I’ve not been happy with how quickly the unit has reported a temp, and it’s usual settled on the second and third scans when I have taken the whole three secs to get around.

 Withings Thermo

As mentioned before, in-ear thermometers can cause a bit of a problem, both in terms of child discomfort, but also accuracy is affected below aged 2.

With the Withings as you move it around the head, there is a slight pulsing vibration from the unit, which then changes to a single long buzz when it has honed in on a temp. We had no issues with the little one waking with either temporal thermometers, but the Braun proved slightly more of a challenge in the one yr old! Even with his own parents, it was a bit of a challenge

Withings Thermo

“What are you doing Dad?? Stop it!! No, I SAID NO!!”

Withings Thermo

“Not that ear! Mother save me! Mother, let me wriggle!!!, MOTHER YOU TRAITOR!”

After the baby challenge, what did we get?

Exergen: 37.1 deg

Withings Thermo

Braun: 36.5

Withings Thermo

Withings Thermo:36.7

Withings Thermo

As you can see, not a huge amount of variation, 0.6 degrees. But from use in the practice, I have seen up to 1 deg measurement variable both ways when using the Braun and the Thermo.

From a medical perspective, I am not going to act purely on the basis of a temperature, but put things in the overall clinical context. This is sometimes while you’ll send patients down to the A&E department, or along for further investigations based on a hunch.

As we’ve seen, no indirect thermometer is accurate enough to base the entirety of a medical management plan, but they can be used to get a “feel” for what is going on.

What about that FDA approval though?

The Withings Thermo has passed through FDA CLEARED and seems very proud of this comment

Withings Thermo

HOWEVER this is a very imported distinction from FDA approved, and the above from Withings site might be considered slightly misleading – so the first question is, what’s the difference?

Cleared medical devices: These medical devices are ones that FDA has determined to be substantially equivalent to another legally marketed device

Approved medical devices: Approved medical devices are those devices for which FDA has approved a premarket approval (PMA) application prior to marketing. This approval process is generally reserved for high-risk medical devices and involves a more rigorous premarket review

Ok, anyone else’s eyes cross over with that?? So we know what the DIFFERENCE between those two statements is, but what does it actually MEAN? Basically that the Thermo is as effective as other temporal scanning thermometers on the market, which we’ve already seen isn’t the gold standard. Conversely, the FDA is saying it is not worse than anything else on the market.


Withings Thermo

The Withings Thermo is an interesting piece of kit. It’s not going to be any better than a similarly priced thermometer (£89), but what is does do, is prompt you via the app to record details, which may be useful for your doctor to see. As we’ve seen the variation can be considerable, but it’s likely you can be reassured if the Thermo is at least showing a normal temperature

The ease of checking a child’s temperature is greatly improved with a temporal scanning device like the Withings Thermo, and a child who is being monitored well is likely going to have a fever picked up sooner than a child with fewer measurements, due to the battle that checking an in ear temperature can be.

On the device side of things, one thing I didn’t like is the white material; it tends to pick up marks very quickly in the bag. However, that may also be a good design feature, encouraging me to clean and disinfect it more often!

Overall the Withings isn’t cheap, which might be it’s the biggest issue. The inclusion of the app might also be considered an excess engineering step. BUT if your little one is unwell, then I think a temporal scanning thermometer can be quite a useful aid, but only if you can afford it – remember this is likely a device to remain in a cupboard, unused for most of the year!



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  2. What’s also good with this is good integration with Apple HealthKit (or equivalent for Android). The temperature gets saved on he phone and can be shown alongside with blood pressure, respiratory rate, weight and compare easily week or month history. It’s good for a patient who want to be proactive in his/her health

    • Hi Heri, you are right on the Health app point, and I’ve added that to the review. However I’d disagree about being proactive on health monitoring depending how you mean. If someone is sick, monitoring the temp is very useful. But there is no indication for general monitoring of temperature day-to-day in a well person, in the way that I monitor weight for example with smart scales.


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