Post on 08-Jun-2020
1 Add date in slide master | © 2017 Roche
Photometric Calibration
Roche User Group 2018Presented by Caroline Roche
2 Add date in slide master | © 2017 Roche
Photometric Calibration
• Photometric calibration curves
• Photometric calibration quality checks
• Photometric calibration methods
3 Add date in slide master | © 2017 Roche
Photometric calibration curves
Linear calibration curve
• Assay absorbances at differentconcentrations form a linear plot
• Linear 2-point
• Linear multipoint (min 3 max 6 standards)
4 Add date in slide master | © 2017 Roche
Photometric calibration curves
Non-linear calibration curve
• Plot of assay absorbances at differentconcentrations form a nonlinear curve
• Multipoint calibration
• Min 3 max 6 standards
• RCM, RCM2T1, RCM2T2, Spline, Line Graph
5 Add date in slide master | © 2017 Roche
Photometric calibration curve parameters
• Calibration curve is mathematically defined by its curve parameters
• In the user interface these are defined as S1 Abs, K, A, B, C
• Linear calibration curve – defined by two parameters S1 Abs and K
• Non linear calibration curve e.g. RCM defined by four parameters
• When an assay is recalibrated software plots the calibration curve using the newly measured values and recalculates these parameters
• Curve parameters displayed in Calibration Status > Calibration Result > Working Information
6 Add date in slide master | © 2017 Roche
Photometric calibration curve parameters
Linear two-point:
S1 Abs = Mean ABS of STD1 Blank
K = K Factor
7 Add date in slide master | © 2017 Roche
K factor (calibration factor)
• K factor is a calibration curve parameter calculated for linear curves.
• Ratio of the difference between the concentration of standards and the difference between the absorbance of the standards.
• For example for two point linear calibration for an end point assay:
K = (Concentration STD2 – Concentration STD1 (blank)) / (Abs STD2 – Abs STD1(blank))
• Used to calculate results from test absorbances
8 Add date in slide master | © 2017 Roche
K factor (calibration factor)
Calibration Working Information Screen – K factor
Always displayed as whole number
Automatically rounded and multiplied by the correct factor of 10 according to the number of decimalplaces set for STD 1 (blank)
9 Add date in slide master | © 2017 Roche
Photometric calibration curve parameters• Example – 2 point linear calibration
10 Add date in slide master | © 2017 Roche
Photometric calibration curve parameters
RCM non-Linear Multipoint
S1 Abs: curve parameter a
K: curve parameter b
A: curve parameter c
B: curve parameter d
11 Add date in slide master | © 2017 Roche
Photometric calibration curve parameters• Example – RCM non linear multipoint calibration
12 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
13 Add date in slide master | © 2017 Roche
Photometric calibration quality checksSD Limit
Non-linear and multipoint linear calibration curves
Absorbance is calculated from givenconcentration using calibration curve for eachstandard and is compared to measuredabsorbance
SD.E alarm generated if exceeds SD limit
Affected standard is flagged on calibration monitor
14 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
SD Limit
15 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
Duplicate Limit
Precision check on duplicate measurements
Calculates % error and absolute absorbance errorbetween duplicate calibrator measurements
Evaluates absolute error first, if this is out of range evaluates % error
Dup.E alarm generated If both out of range
Affected standard is flagged on calibration monitor
16 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
Sensitivity Limit
Ratio of the absorbance difference to the concentration difference
(ABS Span STD – ABS Blank STD) / (Conc SpanSTD – Conc Blank STD)
Upper and lower limit defined in Application/Calib screen
Sens.E alarm generated
17 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
S1 Absorbance Limit
Check on blank calibrator absorbance
S1 A.E Alarm generated if falls outside limits
Range of -32000 to 32000 indicates that thischeck is omitted
18 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
Std. Check
Std.E alarm issued if any of the listed data alarms occur in a calibration (cobas 6000)
19 Add date in slide master | © 2017 Roche
Photometric calibration quality checks
20 Add date in slide master | © 2017 Roche
Calibration methods
2 Point
Full
Blank
Span
21 Add date in slide master | © 2017 Roche
Calibration methods
22 Add date in slide master | © 2017 Roche
Span CalibrationUpdate Type – Difference
Absorbance difference for the measured calibrator is added to each calibrator’s value. Calibration curve is moved up or down maintaining slope.
Update Type – Rate
Ratio of new absorbance value to previous yields an adjustment factor. Each calibrator absorbance is multiplied by this factor.
23 Add date in slide master | © 2017 Roche
24 Add date in slide master | © 2017 Roche
Doing now what patients need next