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BRS Pathology 24 Interpretation of Diagnostic Tests Laboratory Statistic
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BRS Pathology 24 Interpretation of Diagnostic Tests Laboratory Statistic
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BRS Pathology 24 - Interpretation of Diagnostic Tests: Laboratory Statis1. The answer is A. Sensitivity is defined as the ability of a test to be positive
in patients with a specific disease; it is the percentage of known positives
who actually test positive. It is calculated by dividing the number of positive
results in patients (TP) by the total number of patients (TP 1FN).: A worker in
a research laboratory is developing a new diagnostic procedure making use of a
newly discovered marker protein for ovarian cancer. The laboratory has at its
disposal 1,000 preserved serum samples from patients who are known to have
had this tumor. The percentage of the samples that test positive with this new
procedure is referred to as the (A) sensitivity.
(B) specificity.
(C) precision.
(D) accuracy.
(E) predictive value.
2. The answer is B. Specificity is defined as the ability of a test to be
negative in healthy persons; it is the percentage of known negatives who
actually test negative. It is calculated by dividing the number of negative
results in healthy persons (TN) by the total number of healthy persons (TN
1FP).: Conversely, the same laboratory has at its disposal 1,000 similarly
preserved serum samples from normal subjects who are known not to have had
ovarian cancer. The ability of the new procedure to correctly identify these
individuals as normal is referred to as (A) sensitivity.
(B) specificity.
(C) precision.
(D) accuracy.
(E) predictive value.
3. The answer is D. Sensitivity is defined as the probability that a test will be
positive in individuals who are already known to have disease (ovarian
cancer) and is stated to be 90%.: A biotechnology company has just released a
new blood screening test for ovarian cancer. The test is positive in 90% of all
women with ovarian cancer and negative in 80% of women without ovarian
cancer. The prevalence of ovarian cancer in the study population of 1,000 women
is 30%. What is the sensitivity of this test?
(A) 32.5%
(B) 66%
(C) 80%
(D) 90%
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, BRS Pathology 24 - Interpretation of Diagnostic Tests: Laboratory Statis
(E) 95%
4. The answer is C. Specificity is defined as the probability that a test will be
negative in individuals who are already known to be healthy (no ovarian
cancer) and is stated to be 80%.: A biotechnology company has just released a
new blood screening test for ovarian cancer. The test is positive in 90% of all
women with ovarian cancer and negative in 80% of women without ovarian
cancer. The prevalence of ovarian cancer in the study population of 1,000 women
is 30%. What is the specificity of this test?
(A) 32.5%
(B) 66%
(C) 80%
(D) 90%(E) 95%
5. The answer is B. The positive predictive value is the probability that a
woman with a positive test actually has the disease in question. In this
example, there are 410 women (270 TP [90% of 300] 1140 FP [20% of 700])
who had a positive test result. The ratio of TP to all positives (TP 1FP) is
270/410, or 66%.: A biotechnology company has just released a new blood
screening test for ovarian cancer. The test is positive in 90% of all women with
ovarian cancer and negative in 80% of women without ovarian cancer. The
prevalence of ovarian cancer in the study population of 1,000 women is 30%.
What is the positive predictive value of this test?
(A) 32.5%
(B) 66%
(C) 80%
(D) 90%(E) 95%
6. The answer is E. The negative predictive value is the probability that a
woman with a negative test does nothave the disease in question. In this
example, there are 590 women (560 TN [80% of 700] 130 FN [10% of 300])
who had a negative test result. The ratio of TN to all negatives (TN 1FN) is
560/590, or 95%.: A biotechnology company has just released a new blood
screening test for ovarian cancer. The test is positive in 90% of all women with
ovarian cancer and negative in 80% of women without ovarian cancer. The
prevalence of ovarian cancer in the study population of 1,000 women is 30%.
What is the negative predictive value of this test?
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