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Scanner Variability

Scanner Variability. Scanner Variability. Error Specification = +/- 3000 Definition: 1 Standard Deviation (STD) or 1 sigma ( s ) = 3000 Example: One individual scanned on multiple instruments - 30 consecutive times. 10 9 8 7 6 5 4 3 2 1. Frequency.

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Scanner Variability

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  1. Scanner Variability

  2. Scanner Variability • Error Specification = +/- 3000 • Definition: 1 Standard Deviation (STD) or 1 sigma (s) = 3000 • Example: One individual scanned on multiple instruments - 30 consecutive times.

  3. 10 9 8 7 6 5 4 3 2 1 Frequency 31 34 37 40 43 46 49 SCS (Thousands)

  4. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  5. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  6. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  7. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  8. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  9. Frequency 31 34 37 40 43 46 49 10 9 8 7 6 5 4 3 2 1 SCS (Thousands)

  10. Frequency 31 34 37 40 43 46 49 Graph based on 30 Scans SCS (Thousands) What if we scanned this same person 10,000 times?

  11. Frequency 31 34 37 40 43 46 49 Standard DeviationMeasure of the “Spread-outness” of your data 10 - What % of the scans will fall within 1 sigma (Red)? 68 % 4 - 1- SCS (Thousands)

  12. Frequency 31 34 37 40 43 46 49 Standard DeviationMeasure of the “Spread-outness” of your data 10 - What % of the scans will fall within 2 sigma (Red + Green)? 95 % 4 - 1- SCS (Thousands)

  13. Frequency 31 34 37 40 43 46 49 Standard DeviationMeasure of the “Spread-outness” of your data 10 - What % of the scans will fall within 3 sigma (Red + Green + Blue)? 99% 4 - 1- SCS (Thousands)

  14. Successive Scan Differences Question: What is the probability of two successive measurements being very different? • Difference of:Frequency is: • 3000 47.8 % • 6000 15.8 % • 9000 3.4 % • Note: Standard Deviation = +/- 3000

  15. Variation Exists in Biological Measurements Example: Fasting Blood Glucose (FBG) Levels Hypo Glycemia Normal Pre Diabetic Diabetes Mellitus 0 64 110 126 Milligrams / Deciliter (mg/dL)

  16. How Does this Compare to the Scanner? Percentage of readings within a defined range of the actual value Scanner (40,000) 49.1 99.2 0.8 118 Scanner (30,000) 38.3 95.5 4.5 118 Scanner (20,000) 25.9 81.7 18.3 118

  17. Conclusion • Variability is similar or better than typical FDA approved instruments measuring trace compounds in a biological matrix • With measurements such as this it is critical to focus on the Zone and not the specific number • The scale shifts the focus toward the “Zone” concept and away from the number

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