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|Prompt=Two medical teams from France and Russia are conducting a similar study that aims to detect an association between vitamin K deficiency and osteoporosis. Both teams are using the same test kit that is designed to measure vitamin K level in the blood. While the sensitivity of the test is 90%, its specificity is found to be 85%. According to previous studies, the prevalence of vitamin K deficiency is higher in Russia than it is in France. | |Prompt=Two medical teams from France and Russia are conducting a similar study that aims to detect an association between vitamin K deficiency and osteoporosis. Both teams are using the same test kit that is designed to measure vitamin K level in the blood. While the sensitivity of the test is 90%, its specificity is found to be 85%. According to previous studies, the prevalence of vitamin K deficiency is higher in Russia than it is in France. | ||
Based on the previous information, which of the following statements is correct? | Based on the previous information, which of the following statements is correct? | ||
|Explanation=The [[positive predictive value]] (PPV) is used to indicate the probability that in case of a positive test, the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. | |||
Educational objective: The PPV depends on the [[sensitivity]], [[specificity]] and [[prevalence]] of the tested item. | |||
Educational objective: The PPV depends on the sensitivity, specificity and prevalence of the tested item. | |AnswerA=The ability of the test to detect vitamin K deficiency in people who really have a low [[vitamin K]] level is higher in Russia that it is in France. | ||
|AnswerA=The ability of the test to detect vitamin K deficiency in people who really have a low vitamin K level is higher in Russia that it is in France. | |||
|AnswerAExp=The ability of the test to detect [[vitamin K]] deficiency in people who really have a low vitamin K level refers to the sensitivity of the test. The [[sensitivity]] of the test was mentioned to be 90% and this value is constant for a particular test. The sensitivity of this test is independent from the prevalence of vitamin K deficiency. | |AnswerAExp=The ability of the test to detect [[vitamin K]] deficiency in people who really have a low vitamin K level refers to the sensitivity of the test. The [[sensitivity]] of the test was mentioned to be 90% and this value is constant for a particular test. The sensitivity of this test is independent from the prevalence of vitamin K deficiency. | ||
|AnswerB=The positive predictive value of the test is the same in France and Russia. | |AnswerB=The positive predictive value of the test is the same in France and Russia. | ||
|AnswerBExp=The positive predictive value (PPV) is used to indicate the probability that in case of a positive test, the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the [[sensitivity]], [[specificity]] and [[prevalence]] of the tested item. Since the prevalence of vitamin K deficiency is different in Russia than it is in France, then the PPV is not the same in these two different countries. | |AnswerBExp=The [[positive predictive value]] (PPV) is used to indicate the probability that in case of a positive test, the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the [[sensitivity]], [[specificity]] and [[prevalence]] of the tested item. Since the prevalence of vitamin K deficiency is different in Russia than it is in France, then the PPV is not the same in these two different countries. | ||
|AnswerC=The positive predictive value of the test is higher in Russia that it is in France. | |AnswerC=The positive predictive value of the test is higher in Russia that it is in France. | ||
|AnswerCExp=The positive predictive value (PPV) is used to indicate the probability that in case of a positive test, that the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the sensitivity, specificity and prevalence of the tested item. Since the [[prevalence]] of vitamin K deficiency is higher in Russia than it is in France, then the PPV of this test is higher in Russia than it is in France. | |AnswerCExp=The [[positive predictive value]] (PPV) is used to indicate the probability that in case of a positive test, that the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the sensitivity, specificity and prevalence of the tested item. Since the [[prevalence]] of vitamin K deficiency is higher in Russia than it is in France, then the PPV of this test is higher in Russia than it is in France. | ||
|AnswerD=If the test is positive, the probability that the person truly has vitamin K deficiency is higher in France than it is in Russia. | |AnswerD=If the test is positive, the probability that the person truly has vitamin K deficiency is higher in France than it is in Russia. | ||
|AnswerDExp=The PPV depends on the [[sensitivity]], [[specificity]] and [[prevalence]] of the tested item. Since the prevalence of vitamin K deficiency is lower in France than it is in Russia, then the PPV of this test is lower in France than it is in Russia. | |AnswerDExp=The PPV depends on the [[sensitivity]], [[specificity]] and [[prevalence]] of the tested item. Since the prevalence of vitamin K deficiency is lower in France than it is in Russia, then the PPV of this test is lower in France than it is in Russia. | ||
Revision as of 17:35, 2 September 2013
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biostatistics/ Epidemiology |
| Sub Category | SubCategory::Endocrine |
| Prompt | [[Prompt::Two medical teams from France and Russia are conducting a similar study that aims to detect an association between vitamin K deficiency and osteoporosis. Both teams are using the same test kit that is designed to measure vitamin K level in the blood. While the sensitivity of the test is 90%, its specificity is found to be 85%. According to previous studies, the prevalence of vitamin K deficiency is higher in Russia than it is in France.
Based on the previous information, which of the following statements is correct?]] |
| Answer A | [[AnswerA::The ability of the test to detect vitamin K deficiency in people who really have a low vitamin K level is higher in Russia that it is in France.]] |
| Answer A Explanation | [[AnswerAExp::The ability of the test to detect vitamin K deficiency in people who really have a low vitamin K level refers to the sensitivity of the test. The sensitivity of the test was mentioned to be 90% and this value is constant for a particular test. The sensitivity of this test is independent from the prevalence of vitamin K deficiency.]] |
| Answer B | AnswerB::The positive predictive value of the test is the same in France and Russia. |
| Answer B Explanation | [[AnswerBExp::The positive predictive value (PPV) is used to indicate the probability that in case of a positive test, the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the sensitivity, specificity and prevalence of the tested item. Since the prevalence of vitamin K deficiency is different in Russia than it is in France, then the PPV is not the same in these two different countries.]] |
| Answer C | AnswerC::The positive predictive value of the test is higher in Russia that it is in France. |
| Answer C Explanation | [[AnswerCExp::The positive predictive value (PPV) is used to indicate the probability that in case of a positive test, that the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group. The PPV depends on the sensitivity, specificity and prevalence of the tested item. Since the prevalence of vitamin K deficiency is higher in Russia than it is in France, then the PPV of this test is higher in Russia than it is in France.]] |
| Answer D | AnswerD::If the test is positive, the probability that the person truly has vitamin K deficiency is higher in France than it is in Russia. |
| Answer D Explanation | [[AnswerDExp::The PPV depends on the sensitivity, specificity and prevalence of the tested item. Since the prevalence of vitamin K deficiency is lower in France than it is in Russia, then the PPV of this test is lower in France than it is in Russia.]] |
| Answer E | AnswerE::The positive predictive value of the test does not depend on the sensitivity and specificity. |
| Answer E Explanation | [[AnswerEExp::The PPV depends on the sensitivity, specificity and prevalence of the tested item.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The positive predictive value (PPV) is used to indicate the probability that in case of a positive test, the patient really has the specified disease. PPV is a function of the population sampled whereby a higher yield occurs in a higher risk group.
Educational objective: The PPV depends on the sensitivity, specificity and prevalence of the tested item. |
| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |