WBR0660: Difference between revisions
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|Explanation=The [[number needed to treat]] (NNT) is an [[epidemiology|epidemiological]] measure that refers to the number of patients required to receive a certain treatment for 1 patient to benefit from it. It is the the inverse of the absolute risk reduction (ARR), where ARR is the absolute difference in the event rate between the treatment group (vaccine group) and the control group (placebo group). The ARR can be calculated as follows: | |Explanation=The [[number needed to treat]] (NNT) is an [[epidemiology|epidemiological]] measure that refers to the number of patients required to receive a certain treatment for 1 patient to benefit from it. It is the the inverse of the absolute risk reduction (ARR), where ARR is the absolute difference in the event rate between the treatment group (vaccine group) and the control group (placebo group). The ARR can be calculated as follows: | ||
[[Image:ARRequation.jpg| | [[Image:ARRequation.jpg|800px]] | ||
Shown below is a detailed explanation of the calculation of NNT:<br> | Shown below is a detailed explanation of the calculation of NNT:<br> | ||
Rate of HEV development in the vaccine group: (1/50) | Rate of HEV development in the vaccine group: (1/50) x 100 = 2%<br> | ||
Rate of HEV development in the placebo group: (7/50) | Rate of HEV development in the placebo group: (7/50) x 100 = 14%<br> | ||
Absolute risk reduction (ARR) = 2 | Absolute risk reduction (ARR) = 14 - 2 = 12% = 0.12 | ||
NNT = 1/0.12 = 8.33 patients | NNT = 1/0.12 = 8.33 patients | ||
|AnswerA=1.14 | |AnswerA=1.14 | ||
|AnswerAExp=1.14 is not the number needed to treat | |AnswerAExp=1.14 is not the number needed to treat | ||
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|AnswerEExp=Given the equation below, all variables are available to calculate the number needed to treat. | |AnswerEExp=Given the equation below, all variables are available to calculate the number needed to treat. | ||
|EducationalObjectives=The [[number needed to treat]] (NNT) is an [[epidemiology|epidemiological]] measure that refers to the number of patients required to receive a certain treatment for 1 patient to benefit from it. NNT is defined as the inverse of the absolute risk reduction (1/ARR). | |EducationalObjectives=The [[number needed to treat]] (NNT) is an [[epidemiology|epidemiological]] measure that refers to the number of patients required to receive a certain treatment for 1 patient to benefit from it. NNT is defined as the inverse of the absolute risk reduction (1/ARR). | ||
[[Image:ARRequation.jpg|800px]] | |||
|References=First Aid 2014 page 53 | |References=First Aid 2014 page 53 | ||
|RightAnswer=C | |RightAnswer=C | ||
Revision as of 17:20, 17 September 2014
| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian and Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biostatistics/Epidemiology |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A new vaccine is being developed for the prevention of Hepatitis E. In a phase 2 clinical trial, 100 individuals with negative Hepatitis E IgM and IgG anti-HEV antibodies are randomized to receive either the vaccine or placebo. Out of the 50 patients that received the vaccine, 1 went on to develop Hepatitis E in the 6 month follow-up after the vaccination. In the placebo group, 7 out of 50 patients developed Hepatitis E. What is the number needed to treat for this newly developed vaccine according to the results of this trial?]] |
| Answer A | AnswerA::1.14 |
| Answer A Explanation | AnswerAExp::1.14 is not the number needed to treat |
| Answer B | AnswerB::7.14 |
| Answer B Explanation | AnswerBExp::7.14 is not the number needed to treat |
| Answer C | AnswerC::8.33 |
| Answer C Explanation | AnswerCExp::The number needed to treat according to this trial is 8.33 patients |
| Answer D | AnswerD::300 |
| Answer D Explanation | AnswerDExp::300 is not the number needed to treat |
| Answer E | AnswerE::Data insufficient to calculate |
| Answer E Explanation | AnswerEExp::Given the equation below, all variables are available to calculate the number needed to treat. |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::The number needed to treat (NNT) is an epidemiological measure that refers to the number of patients required to receive a certain treatment for 1 patient to benefit from it. It is the the inverse of the absolute risk reduction (ARR), where ARR is the absolute difference in the event rate between the treatment group (vaccine group) and the control group (placebo group). The ARR can be calculated as follows:
Shown below is a detailed explanation of the calculation of NNT:
|
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Number needed to treat, WBRKeyword::Absolute risk reduction, WBRKeyword::HEV, WBRKeyword::Trial, WBRKeyword::Vaccine, WBRKeyword::Placebo, WBRKeyword::NNT |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
