Terminology

Accuracy

• Defines how close the result is to the ‘true’ value

Precision

• The reproducibility of an analytical result

Internal Quality Control (IQC)

• Expected results are known, actual results compared with previous results
• Allows precision to be calculated

External QC

• Samples are circulated by an external lab to lots of NHS biochem labs - expected results are not known to staff when they are analyzing the samples
• The results of what everyone found are circulated and method mean usually taken as the ‘true’ result

Diagnosis

Sensitivity

• Tells you how good the test is at identifying disease
• Most important characteristic of a biochemical test

Specificity

• Measure of how good the test is at identifying heath

Positive Predictive Value (PPV)

• The percentage of people with a positive test who have the disease

Negative Predictive Value (NPV)