Module 4 Flashcards
What are the five steps of introducing a new method or instrument?
Selection
Evaluation
Implementation
Maintenance
Quality control
What factors should be considered when selecting a method?
Application- cost, types of samples, TAT, equipment requirements, personnel requirements, space, portability, safety and hazard precautions, waste requirements, support available, electricity and plumbing requirements
Methodology- what analyte is tested, what is the test principle, how does it compare to the current method, how is it calibrated, stability of reagents, calibrators and controls
Performance- precision and accuracy, can small amounts be detected, interfering substances, change to current reference intervals
Why is method evaluation necessary?
To ensure it has acceptable minimal analytical errors
Error assessment
TE must be less than TEa
What are the error types?
Random- imprecision
Systematic- inaccuracy
Constant- inaccuracy (same over concentrations)
Proportional- inaccuracy (changes as concentration changes)
Total- SE and RE
Total allowable- not detected during evaluation but has to be established
What are the steps of method evaluation?
Familiarization
Determination of stability (calibrators, controls, reagents)
Perform validation assessments (most are quantitative)
What are the different validation assessments? What do they validate?
Linearity- reportable range of method
Method comparison- accuracy (at least 40 specimens for both methods)
Clinical correlation- accuracy (match diagnosis or symptoms = predictive value)
Within run application- precision (three samples analyzed at least 10 times)
Between run replication- precision (three samples analyzed at least 10 times)
MDL- analytic sensitivity (use low levels of analyte)
Interfering substances and cross reactivity- analytic specificity
Stability study- specimen stability (same results over a period of time)
Carryover study- carryover (test high followed by low)
Reference interval determination- reference intervals (set according to population being served, test >100)
What are the steps in method implementation?
Write SOP
Define QC procedures to monitor routine performance
Training (document)
Put method into use
Monitor closely
Identify sources of problems
Establish preventative maintenance procedures
Communicate to other professionals when there is a new or changed method
Why may changes to methods or instruments be implemented?
Improve accuracy and precision
Allow automation
Reduce reagent or labour cost
Measure a new analyte
