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Re: [IP] One Touch Ultra and varying consecutive readings - comments?



THIS MESSAGE HAS BEEN POSTED TWO DAYS LATE. THE IP LIST REFUSED MESSAGES 
FROM MY ORIGINAL E-MAIL ADDRESS: email @ redacted MY SUBSCRIPTION 
ADDRESS HAS BEEN CHANGED TO email @ redacted

Hi, Curtis.

>You are correct in pointing out the difference between accuracy and precision.

Yeah, well I got confused at the beginning of this thread and, among 
others, treated it as an accuracy question. Tisn't. Your post woke me up.

>How does the precision of the Ultra compare with that of other meters?

Good question. I found the package insert for the standard One Touch strips 
here:

http://www.lifescan.com/pdf/ot_teststrip_insert.pdf

It contains the following precision results: CV of 3.4% at 160 mg/dl and 
4.0% at 406 mg/dl, which is considerably higher than the Ultra. Assuming a 
CV of 3.5% at 300 mg/dl and a normal distribution of measurements about the 
mean, meter readings would range from 270-330 over 99% of the time, 280-320 
over 95% of the time, and 290-310 over two-thirds of the time. That range 
is still short of what Catherine measured, which was a range of 280-340 
(again, for what she assumes was the same bg). The precision results tell 
us that it is *very unlikely* to have such results from a meter that 
performs to specifications. The causes of variation include the samples, 
the procedure, and the meter.

>Perhaps Catherine could test twice from the same drop, rapidly.

A concern was voiced about not wanting to have to conduct extra tests in 
order to feel comfortable with an analyzer, especially since this problem 
didn't manifest itself with her old one.

As I responded to her, IMHO changing analyzers is a delicate proposition.

regards, Andy
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