Temp readings not accurate

The Rapid mode of the Welch Allyn Thermometer is also called Predict mode. All predictive thermometers utilize a software algorithm to “predict” what the patient’s temperature would have been after 3-5 minutes, and Welch Allyn 692 thermometers are no exception. se software algorithms vary company to company and the better quality thermometers tend to have a better algorithm based on a wider base sampling size of patients and their conditions.

So onto the likely reasons you are seeing temperature variations:

When the thermometer probe is placed in the patient temperature site, the probe is generally cooler than the patient temperature site and the patient is generally warmer. Because of this, patient heat is transferred to the probe, causing the patient’s body site to be cooled. Welch Allyn thermometers utilize an electronic tip warmer in their probes to compensate somewhat for this temperature difference. The body site typically takes approximately 20 minutes to fully recover and return to its original site temperature after a temperature reading is taken.

If repeat Rapid mode temperatures are taken at the same site prior to the 20-minute site recovery time, the temperature readings will most likley be different for each reading.  If another thermometer is used to testexact  body temperature at the same site prior to the 20-minute site recovery time, that reading too will also be different. This hopefully explains why you had a 0.4C temperature variance as you took successive measurements in the Rapid mode at the same site.

You'll find this temperature variance to be true regardless of what brand electronic thermometer is used in Rapid mode or a mode that gives a reading in less than the 3-5 minute Monitor mode reading the Welch Allyn 692 has. Monitor mode is very similar to traditional glass mercury thermometers, where the thermometer can be left in place for 3-5 minutes to allow it to come to thermal equilibrium (or for the probe and the mouth to come to the same temperature) to give you a “true” and accurate temperature.

Another thing that can cause temperature variance, especially in Rapid mode, is using the temperature same probe cover more than once. The cover will retain heat, although only a small fraction of a degree. Also, the probe cover is stretched over the probe to reduce the air gap which can also cause temperature variation especially in Rapid mode. Introduction of an air gap will cause a temperature variance, again although by a fraction of a degree.

I hope this explain why you are seeing temperature variances between the two modes and variances when you take successive Rapid mode readings.    Let me know if there’s anything else you need help with.   - Cipher

Cipher,   Thanks for you reply.   I am aware of the changes caused by the probe and the predictive algorithms.   In my case, I did not attempt multiple rapid readings close together because of that.  I took a single rapid reading, and then I put the unit in monitor mode and waited the three minutes for it to fully settle.   As I understand, this should give me an accurate reading.   The rapid reading differs from the monitor mode reading by about 1 degree F.   I tried this several times at different times of the day, and always got similar differences.  I also made sure I had not drunk any water or eaten anything for 30 minutes or more.  That indicates to me that the rapid predictive algorithm is frequently a degree or even more off.   This is not what I would expect from a standard clinical device.

A 1.0 F degree variation, especially uitlizing a rapid predictive temp scan, is not clincially significant when rapidly assessing a person's core body temperature.  Whenever a rapid scan reading is in doubt, a clinician will always change to monitor mode to obtain a more accurate reading.   There's just too many viarations in the device algorithims to account for every possible variation between people, which will get close to the accuracy of Monitor mode readings.   Time and stability are the twogreatest issues.  I believe that if you run the same test you mentioned on other people, you may notice that the temp variation between Rapid and Monitor modes may be greater for some and less for others.  

Just out of curiosity, what color probe are you utilizing and what mode are you in ; ORAL, ADULT AXILLARY, or PED AXILLARY?    -Cipher

I am using the blue probe, and I have only tried oral mode. 

After having these issues, I did more research and discovered the Filac 3000 AD, which is similar.   However, that unit is speced to read within 1 degree C even in its fast mode, which is only slightly longer (about 6 seconds instead of 3 seconds) than the Sure Temp fast mode.   I noticed the Filac has an even faster mode (Rabbit), but they spec that mode as only +- 0.5 degrees F.  

Different companies seem to use different approaches.   I understand the challenges of fast predictions.   I just think that Welch Allyn should make it clear that the "normal" readings can vary by a degree F or more at least for some people.   I purchased the professional unit primarily for accurate readings (the cheaper ones were off from 0.5 to 1 degree), so I now feel mislead to find I cannot count on accurate readings unless I wait 3 minutes in monitor mode.