Analytical Properties of Assays

Question 1

Analytical Accuracy

Answer 1

The ability of an assay to get agreement between the measured value and the true value

Question 2

Analytical Precision

Answer 2

The ability of a test to get the same result if a sample is analyzed several times

Question 3

Reliable Laboratory Test Results

Answer 3

The quality of the results being produced must be monitored so that they are both accurate and precise

Question 4

Analytical Specificity

Answer 4

The ability of an assay to identify only the analyte of interest form other substances

Question 5

Analytical Sensitivity

Answer 5

How much change in the analyte concentration is required for the assay to see the change

Question 6

Detection Limit

Answer 6

The lowest concentration of a substance that can be accurately detected by the assay

Question 7

Purpose of Quality Assurance (QA) and Quality Control (QC)

Answer 7

• To detect unacceptable error in the test
• Run Control Samples
  
  • positive, negative, different values for quantitative assays
  • At regular, previously determined intervals
  • Along with the samples from patients
  • Control samples are similar to those from patients

Question 8

Pre-analytical errors

Answer 8

Most common

sample collection

Sample handling

Sample labeling

Question 9

Analytical Errors

Answer 9

Method inappropriate for species

Reagents deteriorated

Poor laboratory technique

Poor maintenance of instruments

Interferences ( false positive or negative)

Question 10

Post-analytical Errors

Answer 10

Transcriptional errors

Report filed with wrong case

Inappropriate reference intervals

Question 11

How much can lab data tell us?

Answer 11

• Individual test results rarely provide a specific diagnosis
• Grouping results may improve the specificity of the process
• History, physical exam findings, and other diagnostic procedures to make a diagnosis
  
  • Patterns of abnormal test results often suggest which tissue or organ systems are affected, which pathologic processes are occurring, or both
• Monitoring sequential changes in data may be helpful
• Negative findings help rule out disease

Question 12

Data interpretation:

Important things you will learn along the way

Answer 12

1. How reproducibility affects data interpretation
   
   1. variation of repeated testing should be minimal but WILL be there
2. Magnitude of change associated with disease
   
   1. small changes are significant with some tests and analytes but not with others
3. Relationships or interdependency between diagnostic tests
   
   1. tests are more meaningful whe interpreted in groups