Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Next revision		 Previous revision
nnt [2025/02/07 14:56] – created andrewtaustinnnt [2025/02/07 15:09] (current) – [Numbers Needed to Treat (NNT)] andrewtaustin
Line 1: Line 1:
-====== Numbers Needed to Treat (NNT) ====== +{{tag>Related}} 
 + ====== Numbers Needed to Treat (NNT) ====== 
  
 The Number Needed to Treat (NNT) is an important concept in evidence-based medicine (EBM). It represents the average number of patients who must be treated with a specific therapy or intervention for one additional patient to benefit compared to a control group (often a placebo or standard of care). The NNT is derived as the inverse of the Absolute Risk Reduction (ARR), providing a practical measure of clinical effectiveness. The Number Needed to Treat (NNT) is an important concept in evidence-based medicine (EBM). It represents the average number of patients who must be treated with a specific therapy or intervention for one additional patient to benefit compared to a control group (often a placebo or standard of care). The NNT is derived as the inverse of the Absolute Risk Reduction (ARR), providing a practical measure of clinical effectiveness.
 +
 +In short, NNT represents the number of patients who must be treated to prevent one additional negative outcome or achieve one additional positive outcome.
  
 ===== Definition and Calculation ===== ===== Definition and Calculation =====
  
-Absolute Risk (AR): The proportion of patients experiencing an event in a group (e.g., 10% of patients have a heart attack in a control group). +**Absolute Risk (AR)**: The proportion of patients experiencing an event in a group (e.g., 10% of patients have a heart attack in a control group). 
-Absolute Risk Reduction (ARR): The difference in the absolute risk between the treatment group and the control group. + 
-Formula: //ARR = AR_control - AR_treatment// +**Absolute Risk Reduction (ARR)**: The difference in the absolute risk between the treatment group and the control group. 
-Number Needed to Treat (NNT): The inverse of the absolute risk reduction. + 
-Formula: //NNT = 1 / ARR//+**Formula**: //ARR = AR_control - AR_treatment// 
 + 
 +**Number Needed to Treat (NNT)**: The inverse of the absolute risk reduction. 
 + 
 +**Formula**: //NNT = 1 / ARR// 
 For example, if the incidence of a particular outcome (e.g., myocardial infarction) in a control group is 10% and the incidence in the treatment group is 5%, the ARR is 0.05 (or 5%).  For example, if the incidence of a particular outcome (e.g., myocardial infarction) in a control group is 10% and the incidence in the treatment group is 5%, the ARR is 0.05 (or 5%). 
  
Line 28: Line 36:
 Below are illustrative examples (approximate values) of interventions with relatively low NNTs: Below are illustrative examples (approximate values) of interventions with relatively low NNTs:
  
-Antibiotics for Bacterial Pneumonia+**Antibiotics for Bacterial Pneumonia**:
 NNT can be as low as around 5 for preventing serious complications in susceptible populations. The high impact of appropriate antibiotic therapy in an acute setting leads to a favourable NNT. NNT can be as low as around 5 for preventing serious complications in susceptible populations. The high impact of appropriate antibiotic therapy in an acute setting leads to a favourable NNT.
  
-Smoking Cessation Interventions in High-Risk Patients+**Smoking Cessation Interventions in High-Risk Patients**:
 Intensive behavioural therapy combined with pharmacotherapy (e.g., nicotine replacement, varenicline) might have an NNT between 5 and 10 for achieving long-term abstinence. The benefit of reducing morbidity is substantial, given the high baseline risk of smoking-related diseases. Intensive behavioural therapy combined with pharmacotherapy (e.g., nicotine replacement, varenicline) might have an NNT between 5 and 10 for achieving long-term abstinence. The benefit of reducing morbidity is substantial, given the high baseline risk of smoking-related diseases.
  
-Vaccinations (e.g., Influenza in Elderly or High-Risk Populations)+**Vaccinations (e.g., Influenza in Elderly or High-Risk Populations)**:
 Depending on the population, seasonal influenza vaccination can have an NNT ranging from around 12 to 40 to prevent one case of influenza, though these numbers vary widely by season, vaccine match, and patient comorbidities. During severe flu seasons or in particularly vulnerable groups, the NNT can be pretty low. Depending on the population, seasonal influenza vaccination can have an NNT ranging from around 12 to 40 to prevent one case of influenza, though these numbers vary widely by season, vaccine match, and patient comorbidities. During severe flu seasons or in particularly vulnerable groups, the NNT can be pretty low.
  
Line 40: Line 48:
 Some therapies or preventive measures show benefits only when administered broadly or for long durations; these often come with higher NNTs: Some therapies or preventive measures show benefits only when administered broadly or for long durations; these often come with higher NNTs:
  
-**Statins for Primary Prevention of Cardiovascular Disease**+**Statins for Primary Prevention of Cardiovascular Disease**:
 In individuals without established cardiovascular disease (low to moderate risk), the NNT for statins to prevent one cardiovascular event over a period of five years can be in the range of 50 to 200, depending on risk factors. Despite a high NNT, statins may still be recommended due to their relatively favourable safety profile and the severity of cardiovascular events. In individuals without established cardiovascular disease (low to moderate risk), the NNT for statins to prevent one cardiovascular event over a period of five years can be in the range of 50 to 200, depending on risk factors. Despite a high NNT, statins may still be recommended due to their relatively favourable safety profile and the severity of cardiovascular events.
  
-**Aspirin for Primary Prevention of Cardiovascular Events in Low-Risk Patients**+**Aspirin for Primary Prevention of Cardiovascular Events in Low-Risk Patients**:
 For individuals at low cardiovascular risk, the NNT to prevent one heart attack or stroke can be over 100. However, this must be weighed against potential harms such as gastrointestinal bleeding. For individuals at low cardiovascular risk, the NNT to prevent one heart attack or stroke can be over 100. However, this must be weighed against potential harms such as gastrointestinal bleeding.
  
-**Screening Mammography for Women Aged 40–49**+**Screening Mammography for Women Aged 40–49**:
 Estimates for the NNT (to prevent one breast cancer death) can be in the hundreds when screening is applied to younger, lower-risk populations. As age and risk factors increase, the NNT typically decreases. Estimates for the NNT (to prevent one breast cancer death) can be in the hundreds when screening is applied to younger, lower-risk populations. As age and risk factors increase, the NNT typically decreases.
  
  • Last modified: 2025/02/07 14:56
  • by andrewtaustin