scanner variability
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Scanner Variability
• Error Specification = +/- 3000• Definition: 1 Standard Deviation (STD) or 1
sigma () = 3000• Example: One individual scanned on multiple
instruments - 30 consecutive times. 38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
Scanner Variability
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
10987654321
SCS (Thousands)
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
38,000 39,000 40,000 41,000 42,000 40,000 34,000 46,000 49,000 43,000 43,000 37,000 38,000 39,000 45,000 34,000 41,000 43,000 44,000 35,000 39,000 40,000 41,000 42,000 31,000 46,000 42,000 36,000 37,000 38,000
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
10987654321
31 34 37 40 43 46 49
Fre
quen
cy
SCS (Thousands)
Graph based on 30 Scans
What if we scanned this same person 10,000 times?
31 34 37 40 43 46 49
Fre
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cy
10 -
4 -
1-
SCS (Thousands)
Standard DeviationMeasure of the “Spread-outness” of your
data
68 %
What % of the scans will fall within 1 sigma (Red)?
What % of the scans will fall within 1 sigma (Red)?
31 34 37 40 43 46 49
Fre
quen
cy
10 -
4 -
1-
SCS (Thousands)
Standard DeviationMeasure of the “Spread-outness” of your
dataWhat % of the scans will fall
within 2 sigma (Red + Green)?
What % of the scans will fall within 2 sigma (Red + Green)?
95 %
31 34 37 40 43 46 49
Fre
quen
cy
10 -
4 -
1-
SCS (Thousands)
Standard DeviationMeasure of the “Spread-outness” of your
data
What % of the scans will fall within 3 sigma (Red + Green
+ Blue)?
What % of the scans will fall within 3 sigma (Red + Green
+ Blue)?
99%
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
Variation Exists in Biological Measurements
Example: Fasting Blood Glucose (FBG) Levels
Hypo Glycemia
NormalPre
DiabeticDiabetes Mellitus
0 64 110 126
Milligrams / Deciliter (mg/dL)
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 118Scanner (30,000) 38.3 95.5 4.5 118Scanner (20,000) 25.9 81.7 18.3 118
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