Glossary of Evidence-Based Medicine and Statistical Terms
| Term | Abbreviation | Definition | |
|---|---|---|---|
| Sensitivity | Sn | Percentage of patients with disease who have a positive test for the disease in question | |
| Specificity | Sp | Percentage of patients without disease who have a negative test for the disease in question | |
| Predictive value (positive and negative) | PV+
PV- |
Percentage of patients with a positive or negative test for a disease who do or do not have the disease in question | |
| Pretest
probability |
Probability of disease before a test is performed | ||
| Post-test
probability |
Probability of disease after a test is performed | ||
| Likelihood ratio | LR | LR |
|
| Relative risk reduction | RRR | The percentage difference in risk or outcomes between treatment and control groups. Example: if mortality is 30 percent in controls and 20 percent with treatment, RRR is (30-20)/30 = 33 percent. | |
| Absolute risk reduction | ARR | The arithmetic difference in risk or outcomes between treatment and control groups. Example: if mortality is 30 percent in controls and 20 percent with treatment, ARR is 30-20=10 percent. | |
| Number needed to treat | NNT | The number of patients who need to receive an intervention instead of the alternative in order for one additional patient to benefit. The NNT is calculated as: 1/ARR. Example: if the ARR is 4 percent, the NNT = 1/4 percent = 1/0.04 = 25. | |
| Number needed to harm | NNH | The number of patients who need to receive an intervention instead of the alternative in order for one additional patient to experience an adverse event. | |
| 95 percent confidence interval | 95% CI | An estimate of certainty. It is 95% certain that the true value lies within the given range. A narrow CI is good. A CI that spans 1.0 calls into question the validity of the result. | |
| Systematic review | A type of review article that uses explicit methods to comprehensively analyze and qualitatively synthesize information from multiple studies | ||
| Meta-analysis | A type of systematic review that uses rigorous statistical methods to quantitatively synthesize the results of multiple similar studies |
