Short teaching lessons
Sensitivity explained with a veterinary exam example
Prepared 23 October 2026 · VetQ
Sensitivity asks: among animals that truly have the condition, what proportion test positive? The denominator contains diseased animals, not all positive test results. Keep the reference disease classification separate from the test result.
For veterinary exam study. These short examples do not prescribe treatment for an individual patient.
Build the disease-positive column
In an invented evaluation, 100 animals truly have a condition according to the reference classification. The new test identifies 90 and misses 10. The 90 are true positives; the 10 are false negatives. Sensitivity is 90 ÷ (90 + 10) = 90%.
Keep the direction of the question clear
Sensitivity describes test results among those with disease. It does not tell you the probability that a positive animal has the disease. That second question uses a different denominator and requires information about false positives and the tested population.
Use false negatives to interpret the result
In this example, ten of every hundred diseased animals in the evaluation were missed. Whether that is acceptable depends on the purpose of testing and the consequences of a miss. Do not apply a study estimate to every species, disease stage or testing situation without checking its relevance.
Build the complete table yourself
Use four cells labelled true positive, false negative, false positive and true negative. Put disease status in columns and test result in rows. For a fictional study, enter 45, 5, 15 and 135 respectively. There are fifty diseased animals, so sensitivity is 45 ÷ 50 = 90%. The fifteen false positives do not enter that denominator. Total all four cells to check that the study contains 200 animals. Then cover the labels and rebuild them from the wording of the question. This simple exercise helps you avoid choosing a familiar formula before deciding which group the question is asking about.
Check your understanding
An invented evaluation includes 80 diseased animals. Sixty-eight test positive. Calculate sensitivity and the number of false negatives.
Read the answer and reasoning
Sensitivity = 68 ÷ 80 = 85%. False negatives = 80 − 68 = 12. The total number of positive results in the whole population is not needed for this calculation.
Keep reading
- Specificity explained with a veterinary exam example
- Why can a positive veterinary test be wrong? Predictive value explained
- Epidemiology and Preventive Medicine exam questions: topics, study tips and free sample questions
Sources and further reading
Source pages checked 23 October 2026. Examples and study routines on this page are original teaching material, not official examination items.