Accuracy of FDA approved oximeters

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dataq1
Posts: 816
Joined: Sat Dec 24, 2005 8:09 am
Location: Northeast Ohio

Accuracy of FDA approved oximeters

Post by dataq1 » Fri Sep 30, 2022 9:18 pm

Embedded in the various discussions about watches and other OTC oximeters has been the notion that FDA approved oximeters are more accurate than non-FDA approved ones.

In the FDA website https://www.fda.gov/medical-devices/saf ... %20values. the accuracy is discussed for FDA approved oximeters.
FDA-cleared prescription pulse oximeters are required to have a minimum average (mean) accuracy that is demonstrated by desaturation studies done on healthy patients. This testing compares the pulse oximeter saturation readings to arterial blood gas saturation readings for values between 70-100%. The typical accuracy (reported as Accuracy Root Mean Square or Arms) of recently FDA-cleared pulse oximeters is within 2 to 3% of arterial blood gas values. This generally means that during testing, about 66% of SpO2 values were within 2 or 3% of blood gas values and about 95% of SpO2 values were within 4 to 6% of blood gas values, respectively.

However, real-world accuracy may differ from accuracy in the lab setting. While reported accuracy is an average of all patients in the test sample, there are individual variations among patients. The SpO2 reading should always be considered an estimate of oxygen saturation. For example, if an FDA-cleared pulse oximeter reads 90%, then the true oxygen saturation in the blood is generally between 86-94%. Pulse oximeter accuracy is highest at saturations of 90-100%, intermediate at 80-90%, and lowest below 80%. Due to accuracy limitations at the individual level, SpO2 provides more utility for trends over time instead of absolute thresholds. Additionally, the FDA only reviews the accuracy of prescription use oximeters, not OTC oximeters meant for general wellness or sporting/aviation purposes. (bold emphasis added by FDA)
There are a couple of learning points here:
(1) it is implied that the oximeter readings of an oximeter under test/review are averaged then compared with a laboratory-based arterial blood gas determination for purposes of the analysis.
(2) Clearly states that the acceptable range is 8% (plus 4% or minus 4%) from the blood gas value.
(3) The FDA only reviews (tests?) oximeters that are for prescription-use. (sounds like they will not review/evaluate OTC oximeters.
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Tec5
Posts: 173
Joined: Mon Mar 28, 2022 10:32 am

Re: Accuracy of FDA approved oximeters

Post by Tec5 » Wed Oct 05, 2022 7:33 am

dataq1 wrote:
Fri Sep 30, 2022 9:18 pm
For example, if an FDA-cleared pulse oximeter reads 90%, then the true oxygen saturation in the blood is generally between 86-94%.
Is the reverse also true? That an actual (blood draw test) of 90% is likely to be shown by a "medical grade" pulse-oximeter as any number between 86 and 94?

The problem I sense with that is that a 94 reading could be viewed as inconsequential (requiring no intervention), while an 86 is within the scope of a need for supportive therapy (supplemental O2 or supportive ventilation).

It seems as if the medical grade oximeters are not all that accurate, if the acceptable range is 8 percentage points.
I am neither a physician nor a lawyer, so DO NOT rely on me for professional medical or legal advice.