The only cost effective test available demonstrates a positive predictive value of less than 50%. What...

The only cost effective test available demonstrates a positive predictive value of less than 50%. What ethical and economic concerns do you have about using this test for screening the population for an STD infection? (Consider what we know about the effect of prevalence on predictive value.) This question takes into account that the prevalence is low

Expert Solution

The measure of frequency of occurance of a disease in a specified at risk population at a specific time is called as Prevalence.

Prevalence = Total number of persons with a disease / Population at risk for the disease

For example,if the prevalence of a disease is 1% of the total population, then approximately 1 in 100 people are expected to be affected with that disease before any diagnostic testings. Thus,the Prevalence of a disease have an impact on the positive predictive value (PPV) and negative predictive value (NPV) of tests.

Predictive value of a test is the number of times the result generated were proved to be correct. Positive predictive value(PPV), is the actual percentage of people affected with the disease condition out of those who were tested positive during screening process. Negative Predictive Value (NPV) is the actual percentage of people who are not having a disease out of those who tested negative. Predictive values are effective tools that aids in clinical decision-making as it gives a measurement of possibility of an individual to contract a particular disease. Also the PPV and NPV vary dramatically depending on the prevalence of the condition in the specific population being tested.

Screening tests are considered as the corner stones to secondary prevention. A Periodic health screening helps in early detection a disease. In case of infectious diseases, screening tests contributes to breaking the chain of transmission thus prevent onset of new cases.

Characteristics of good screening test:

Some of the necessary qualities of an effective screening tests are

Simple and quick to administer.
Inexpensive and safe to use.
Readily available and provides access to a proper plan of treatment if results are positive.
Acceptable to the target population.
Needs to be researched adequately and proven to be valid, reliable, and must have good predictive values.

Mass screening for prediction of probability of occurance is important when the incidence of cases are high in a particular set of population. For such a population it is not ethical to administer a test with only half chances of positive predictive values. That means a screening test can be cost-effective if the disease condition is common enough and the test results are accurate enough. A test is considered to be cost-effective also, if the patients who are tested positive have access to effective treatment measures at an affordable cost. A test with only half chances of beigng accurate, definitely cannot be administered to a vulnerable population as it affects the promptness in initiating care measures. Here the population mentioned have a low prevalance rate of STDs. A screening test with high sensitivity,specificity and predictability,may still have a low PPV if the disease prevalence is sufficiently low in the target population.

Nightingale answered 2 years ago

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