0
   

Covid -19 validation trial -HELP!

 
 
Reply Sat 4 Apr, 2020 02:25 am
Dear Stats people, I desperately need your help.
I have created a laser to diagnose Covid-19 but have to supply Stat data for ethics and medical device approval.
May I have your opinion please - because, I know nothing about this field of maths and logic.

In Australia ~250000 tests with 2.14% positive PCR tests. I am hoping to validate the positive side of tests as a negative PCR test does not mean its negative - it just means its negative or you did not acquire the RNA. There is an expectation there may be a 5 to 10 fold greater infection rate than actually tested, partly to not testing and partly to false-negative tests.

So I am assuming in my validation trial I will at least get a doubling of the 2.14% positive rate to 4.28%. Its a guess but I have to choose a figure.

I have used this calculator: https://clincalc.com/stats/samplesize.aspx

Sorry the formula does not paste well

Incidence, population 2.14%
Incidence, study group 4.28%
Alpha 0.05
Beta 0.05
Power 0.95

=p0q0{z1−α/2+z1−βp1q1p0q0−−−√}2(p1−p0)2q0=1−p0q1=1−p1N=0.0214∗0.9786{1.96+1.640.0428∗0.95720.0214∗0.9786−−−−−−−−−√}2(0.0428−0.0214)2

N=830

p0 = proportion (incidence) of population
p1 = proportion (incidence) of study group
N = sample size for study group
α = probability of type I error (usually 0.05)
β = probability of type II error (usually 0.2)
z = critical Z value for a given α or β


So the number of tests is at least N =830 . I was planning on at least 1000
people in the validation trial.

So I have some questions - in Stats - how do you handle this data/present this data? Sorry, I am a complete novice in this field.
eg these are the questions I am being asked :
• Data Analysis: How will you measure, manipulate and/or analyze the information that you collect/gather?
o Matching and sampling strategies
o Accounting for potential bias, confounding factors and missing information
o Statistical power calculation

Thanking you in advance
  • Topic Stats
  • Top Replies
  • Link to this Topic
Type: Question • Score: 0 • Views: 220 • Replies: 2
No top replies

 
engineer
 
  2  
Reply Sat 4 Apr, 2020 07:10 am
@GarryBright,
It sounds like you are trying to test two different populations which is really confounding your study. I suggest you get 20 positive test samples and 20 negative test samples using the existing methodology. Conduct your test on the exact same 40 samples. Your data will divide up into four boxes, YES/YES, YES/NO, NO/YES and NO/NO. If your test is comparable to the existing methodology, you will get a lot of YES/YES and NO/NO, very little in the other boxes. If you get equal in all the boxes, your test is not equivalent to the existing test. 20 each is statistical overkill here but while five of each (with perfect matches of yes and no) would be statistically clear, I'm sure you would have trouble selling it to non-statisticians. You want to avoid getting 2 positive samples and 98 negative samples. That would match real life, but you are testing the capability of the test, not the population. You need to know what your risk of false positive and false negative is compared to the existing test.
GarryBright
 
  1  
Reply Sat 4 Apr, 2020 05:53 pm
@engineer,
Thanks - that sounds logical
0 Replies
 
 

 
  1. Forums
  2. » Covid -19 validation trial -HELP!
Copyright © 2024 MadLab, LLC :: Terms of Service :: Privacy Policy :: Page generated in 0.03 seconds on 10/10/2024 at 04:21:27