Method Selection - Selection of a prospective method for day to day laboratory use

Selection of a method for day to day laboratory analysis by comparing with a prospective method.
Things to consider and assess during method selection.

1. Method Selection Karthik G Kamath K Associate Professor Department of Biochemistry

2. METHOD SELECTION Optimal method selection involves consideration of medical need, analytical performance, and practical criteria

3. Analytical Performance Criteria In evaluation of the performance characteristics of a candidate method (1) precision, (2) accuracy (trueness), (3) analytical range, (4) detection limit, and (5) analytical specificity are of prime importance.

4. introducing a new method into routine use Establish need Definition of quality goal Method selection/development Method verification/ validation Implementation Routine analysis Quality control practices Result report

5. Certain variables water quality, calibration of analytical balances, calibration of volumetric glassware and pipettes etc should be monitored on a laboratory-wide basis because they will affect many of the methods used in the laboratory

6. Choice of Analytical Method initial evaluation of a method often takes place in a setting somewhat more idealized than the production setting

7. it is desirable to have a startup laboratory before test results are to be reported. This period allows time to (1) discover any additional problems, (2) develop maintenance programs that alleviate those problems, and (3) train a sufficient number of analysts to support the routine service operation.

8. Linearity Measure of degree to which a curve approximates a straight line Refers to overall system response An attribute that is distinct for accuracy and precision Measured by testing levels of an analyte that are known relative to each other When results are plotted against these values the degree of curve’s comformance to straight line

9. Assessment of linearity Using samples containing analyte at 5 diff concentration levels in 3x A plot of signals is created, usually by means of regression line Correlation coefficient, y-intercept, slope, and residual sum of squares must be calculated.

10. Assessment of accuracy Several methods are available application of an analytical procedure to an analyte of known purity (e.g. reference material) comparison of the results of the proposed analytical procedure with those of a second well-characterised procedure, the accuracy of which is stated and/or defined 2 results must be compared accuracy may be inferred once precision, linearity and specificity have been established.

11. Assessment of precision Repeatability – A min. 9 determinations covering specified range of procedure (3 concentrations / 3 replicates) A min. 6 determinations at 100% of the test concentration (t he theoretical concentration of a testing substance when you prepare a test solution)

12. Assessment of precision Reproducibility – By inter-laboratory trials (testing same sample by many laboratories) Standardization of an analytical procedure

13. References Tietz textbook of Clinical chemistry and molecular diagnostics Wikipedia.org Slideshare.net Other internet resources