Suppose a study sampled 200 males with prostate cancer and 200 males without pro

Question

Suppose a study sampled 200 males with prostate cancer and 200 males without prostate cancer (a case-control study). A new diagnostic test for detecting prostate cancer is performed in all 400 participants and the results are summarized below. Assume it is known from prior studies, that 30% of men in this population have prostate cancer. What is the estimated sensitivity of the new diagnostic test? What is the estimated specificity of the new diagnostic test? What is the positive predictive value (PPV) of the new diagnostic test? How would your answers to a), b) and c) change if 10% of the men in this population have prostate cancer?

Explanation / Answer

a. Sensitivity=True positive/Total disease=160/(160+40)*100=80%

b. Specificity=True negative/Total non disease=180/(180+20)*100=90%

c. Positive predictive value (PPV)=True positive/Total positive=160/(160+20)*100=88.89%

d. Sensitivity and specificity being characteristics of the test are not influenced much, but prevalance of the disease, affects the positive predictive value. That is with lower prevalance, the positive predicted value will be lower.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.