• Epiville: Screening • Think of hypothetical screening programs for diseases of
ID: 123297 • Letter: #
Question
• Epiville: Screening • Think of hypothetical screening programs for diseases of interest to you; find one example of a disease where high sensitivity would be more important, and one example where high specificity would be more important. • You have probably had the experience of being screened many times (e.g., cholesterol test, glucose level test, blood pressure measurement). What is more important information from a PATIENT's point of view (PPV/NPV vs. Sensitivity/Specificity), and what is more important information from a PHYSICIAN's point of view (PPV/NPV vs. Sensitivity/Specificity). • What are some strategies to reduce lead time bias in studies evaluating the efficacy of screening programs?
Explanation / Answer
Sensitivity:
The term sensitivity is defined as the ability of a test to identify correctly those who have the disease, that is "true Positive". A 90 percent sensitivity means that 90% of diseased people screened by the disease will give a true positive result and the remaining 10% a false positive result
.Specificity:
It is defined as the ability of a test to identify correctly those who do not have the disease, that is "true negatives". A 90% specificity means that 90% of non-diseased persons will give "true negative" result, 10% of non-diseased people screened by the test will be wrongly classified as 'diseased" when they are not.
Evaluation of a screening test:
The following measures used to evaluate the screening test.
Let us compare the sensitivity and specificity of EEG and CAT screening for diagnosis of brain tumours.
Diagnosis of Brain tumors by EEG
Brain Tumors
sensitivity = 36/40*100 = 90 percent.
specificity = 306,000/360,000 *100 = 85 percent.
Diagnosis of Brain tumors by computed assisted axial tomography
Brain tumors
sensitivity =39/40*100 =97.5 percent.
specificity =342,000/360,000*100 =95 percent.
Patient point of view:
Physician point of view:
Strategies to reduce lead time bias:
EEG results present Absent positive 36 54,000 Negative 4 306,000 40 360,000Related Questions
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