Question

1. Describe three characteristic of a screening test that would make the test a "good" test

[ Disease Prevalence and Screening Tests ]

2.Describe how disease prevalence can impact the predictive values of a screening test.

Answer 1

1.The characteristics of a good screening test are

Sensitivity :The test is capable of designating positive case

Specificity :The test is capable of designating negative case

The additional four characteristics are

1. Positive predictive value
2. Negative predictive value
3. Accuracy
4. Likelihood ratio

The other characteristics which can be also used in community are

• Inexpensive :It should be easily available for all without burning out their pocket
• Easy to administer and minimal discomfort :The test should be easy to perform with out making the patient feel anxious or exhausted
• Reliable and Valid:It shoukd be very consistent on whom to be taken for screening and capable of distinguishing sick and non sick people

2.Predictive value is based on the sensitive and specificity test while prevalence refers to the disease occurrence in the area.

It can impact in the following way

The positive predictive value increases with higher prevalence rate and

The negative Predictive value decreases when the prevalence results are increased or higher