Sample Testing

Question 1

Testing process steps

Answer 1

• Receipt of sample
• Analysis
• Validation
• Interpretation
• Authorisation
• Reporting

Question 2

Turnaround time

Answer 2

The time taken between receipt and reporting of a sample

Question 3

Reasons for testing

Answer 3

• To make a diagnosis
• To identify causes of disease
• To monitor disease progress
• To estimate prognosis
• Determine treatment options
• Monitor efficacy of treatment

Question 4

Sensitivity of a test

Answer 4

The percentage of people with the disease who have a positive result

TP/[TP+FN] X100

Question 5

Specificity of a test

Answer 5

The percentage of healthy people who have a negative result

TN/[TN+FP] X100

Question 6

Positive predictive value

Answer 6

The percentage of positive results that are true positives

TP/[TP+FP] X100

Question 7

Negative predictive value

Answer 7

The percentage of negative results that are true negatives

TN/[TN+FN] X100

Question 8

Overall efficiency of a test

Answer 8

[TP + TN] X 100 / Total no. of tests

Question 9

Sources of error

Answer 9

1. Pre-analytical (sample collection)
2. Analytical (lab errors)
3. Post-analytical (calculation/reporting errors)

Question 10

Point of care testing

Answer 10

POCT can be carried out at a range of locations, including at home or in hospital

POCT gives rapid results but they are less subject to validation steps