1.0 PURPOSE:
2.0 SCOPE:
3.0 DEFINITIONS:
3.1 Alert limit: A microbiological limit, when exceeded, indicates that a process may have drifted from its normal operating condition. This warns the condition of the area and an investigation is required but not necessary of a corrective action.
3.2 Action limit: A microbiological limit, when exceeded, indicates that a process drifted from its normal operating condition. A documented investigation program is required to know the route cause and corrective actions derived based on the investigation.
3.3 Standard deviation: A measure of the dispersion of a set of data from its mean. The more spread apart the data, the higher the standard deviation. Standard deviation is calculated as the square root of variance.
4.0 RESPONSIBILITY:
4.1 Analyst /Microbiologist: The Analyst/microbiologist is responsible for execution of the procedure specified in this document.
4.2 Executive /designee: Executive or designee is responsible for review of compiled data and calculating alert and action limits using statistical formulae.
4.3 Head Quality Control: The Head Quality control is responsible for review of the compiled data and ensure that the procedure mentioned in the SOP is followed.
4.4 Quality assurance: The QA is responsible for approval and over all compliance of the procedure mentioned in the SOP.
5.0 PROCEDURE:
5.1 Alert limit and action limits:
5.1.1 Normal distribution method is best used for high counts.
5.1.2 All the test data points are arranged in a histogram by using excel sheet.
5.1.3 Calculate the mean and standard deviation values for test data.
5.1.4 Consider mean + 2 x standard deviation is alert limit for test data.
5.1.5 Consider mean + 3 x standard deviation is action limit for test data.
5.1.6 For the above data mean value is 9.86
5.1.7 Standard deviation for above data is 2.42, hence alert level is 15 and action level is 17 according to the formulae.
5.2 Alert and action limit shall be reviewed periodically (once in 2 years) as a part of routine trend analysis.
5.3 If the existing alert and action limit is stringent than the established alert and action limit, then the revision is not required. The same limit shall be continued further.
5.4 If the established alert and action limit is stringent, than the existing alert and action limit, then the revision may also be required (wherever applicable) or the same limit shall be continued further.
6.0 ABBREVIATIONS:
SOP : Standard operating procedure
QA : Quality assurance
QC : Quality control
Cfu : Colony forming unit
7.0 REFERENCES:
Fundamental of environmental monitoring program PDA technical report —No.13 sept/oct- 2001.
8.0 ANNEXURES:
Nil.