A current acceptance criterion reco

A current acceptance criterion recommended in the pharmacopeias for Precision is based on Coefficient of Variation.
The EZ-Fluo™ method is considered as precise if:
% CV EZ-Fluo™ method≤% CV Traditional method
If the expected coefficient of variation is too high, the corrective actions detailed in section 6.2.6 are applicable.
EZ-Fluo™ Method Linearity
The Linearity of the EZ-Fluo™ method is its ability to produce results that are proportional to the concentration of microorganisms present in a sample, and should be determined over the range of the test.
To evaluate the Linearity, the regression line is determined across the range of the method, and the coefficient of regression(R2)is calculated; R2 gives an estimate of the relationship between EZ-Fluo™ results and traditional Method results.
The Linearity of EZ-Fluo™ method is established from the data recovered during the Accuracy test.
The regression line between the EZ-Fluo™ counts and traditional Method counts should be calculated across the test range as follows:
y=a x+b, where:
y is the average Fluo counts
x is the average Control counts
a is the slope
b is the intercept
The graphic should be done using an appropriate graphical and statistical tool, enabling also the calculation of the regression line equation and coefficient of regression R2.
The graph hereafter is an example of regression between the two methods:
Traditional Method CFU
On this graph example we can observe that:
the regression line is drawn across the range of the method; in the Accuracy test example the theoretical range tested was 0 to 100 CFU;
the regression line equation is y=1.0602x - 0.7495;
the slope is 1.0602;
the intercept is -0.7495;
the coefficient of regression R2 is 0.9988.
The choice of the statistical method(and related acceptance criterion)should be made and documented prior to starting the test.
Depending on the relevant regulations, the acceptance criteria can be related to:
the coefficient of regression R2
As an example, the EZ-Fluo™ method can be considered as linear if:
the regression line between the EZ-Fluo™ counts and traditional Method counts is drawn,
the correlation coefficient is R2≥0,95
the estimated slope is significant:0.8≤a≤1.2


If it is not possible to demonstrate the Linearity of the EZ-Fluo™ method across the complete range, it is possible to decrease the range and to demonstrate the linearity within a more narrow range(using four concentrations instead of the six series initially tested, for example).
If the Linearity does not meet one acceptance criteria, the corrective actions detailed in section 6.2.6 are applicable.
EZ-Fluo™ Method Range
The operational Range of the EZ-Fluo™ method is the interval between the upper and lower levels of microorganisms that have been demonstrated to be determined with Precision, Accuracy, and Linearity.
The effective range of the method is obtained from the effective CFU average observed at the lower and upper concentrations of the range tested.