In epidemiology and biostatistics, the experimental event rate (EER) is a measure of how often a particular statistical event (such as response to a drug, adverse event or death) occurs within the experimental group (non-control group) of an experiment. [1]
This value is very useful in determining the therapeutic benefit or risk to patients in experimental groups, in comparison to patients in placebo or traditionally treated control groups.[ citation needed ]
Three statistical terms rely on EER for their calculation: absolute risk reduction, relative risk reduction and number needed to treat.
The control event rate (CER) is identical to the experimental event rate except that is measured within the scientific control group of an experiment. [2]
In a trial of hypothetical drug "X" where we are measuring event "Z", we have two groups. Our control group (25 people) is given a placebo, and the experimental group (25 people) is given drug "X".
Event "Z" in control group : 4 in 25 people Control event rate : 4/25
Event "Z" in experimental group : 12 in 25 people Experimental event rate : 12/25
Another worked example is as follows:
Example 1: risk reduction | Example 2: risk increase | |||||
---|---|---|---|---|---|---|
Experimental group (E) | Control group (C) | Total | (E) | (C) | Total | |
Events (E) | EE = 15 | CE = 100 | 115 | EE = 75 | CE = 100 | 175 |
Non-events (N) | EN = 135 | CN = 150 | 285 | EN = 75 | CN = 150 | 225 |
Total subjects (S) | ES = EE + EN = 150 | CS = CE + CN = 250 | 400 | ES = 150 | CS = 250 | 400 |
Event rate (ER) | EER = EE / ES = 0.1, or 10% | CER = CE / CS = 0.4, or 40% | EER = 0.5 (50%) | CER = 0.4 (40%) |
Equation | Variable | Abbr. | Example 1 | Example 2 |
---|---|---|---|---|
EER − CER | < 0: absolute risk reduction | ARR | (−)0.3, or (−)30% | N/A |
> 0: absolute risk increase | ARI | N/A | 0.1, or 10% | |
(EER − CER) / CER | < 0: relative risk reduction | RRR | (−)0.75, or (−)75% | N/A |
> 0: relative risk increase | RRI | N/A | 0.25, or 25% | |
1 / (EER − CER) | < 0: number needed to treat | NNT | (−)3.33 | N/A |
> 0: number needed to harm | NNH | N/A | 10 | |
EER / CER | relative risk | RR | 0.25 | 1.25 |
(EE / EN) / (CE / CN) | odds ratio | OR | 0.167 | 1.5 |
EER − CER | attributable risk | AR | (−)0.30, or (−)30% | 0.1, or 10% |
(RR − 1) / RR | attributable risk percent | ARP | N/A | 20% |
1 − RR (or 1 − OR) | preventive fraction | PF | 0.75, or 75% | N/A |
Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments and known interventions that warrant further study and comparison. Clinical trials generate data on dosage, safety and efficacy. They are conducted only after they have received health authority/ethics committee approval in the country where approval of the therapy is sought. These authorities are responsible for vetting the risk/benefit ratio of the trial—their approval does not mean the therapy is 'safe' or effective, only that the trial may be conducted.
The Heart Protection Study was a randomized controlled trial run by the Clinical Trial Service Unit, and funded by the Medical Research Council (MRC) and the British Heart Foundation (BHF) in the United Kingdom. It studied the use of the cholesterol lowering drug, simvastatin 40 mg and vitamin supplementation in people who were at risk of cardiovascular disease. It was led by Jane Armitage, an epidemiologist at the Clinical Trial Service Unit.
Sulfonylureas or sulphonylureas are a class of organic compounds used in medicine and agriculture. The functional group consists of a sulfonyl group (-S(=O)2) with its sulphur atom bonded to nitrogen atom of a ureylene group (N,N-dehydrourea, a urea derivative). The side chains R1 and R2 distinguish various sulfonylureas.
In the design of experiments, hypotheses are applied to experimental units in a treatment group. In comparative experiments, members of a control group receive a standard treatment, a placebo, or no treatment at all. There may be more than one treatment group, more than one control group, or both.
The number needed to treat (NNT) or number needed to treat for an additional beneficial outcome (NNTB) is an epidemiological measure used in communicating the effectiveness of a health-care intervention, typically a treatment with medication. The NNT is the average number of patients who need to be treated to prevent one additional bad outcome. It is defined as the inverse of the absolute risk reduction, and computed as , where is the incidence in the treated (exposed) group, and is the incidence in the control (unexposed) group. This calculation implicitly assumes monotonicity, that is, no individual can be harmed by treatment. The modern approach, based on counterfactual conditionals, relaxes this assumption and yields bounds on NNT.
The relative risk (RR) or risk ratio is the ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group. Together with risk difference and odds ratio, relative risk measures the association between the exposure and the outcome.
Cladribine, sold under the brand name Leustatin, among others, is a medication used to treat hairy cell leukemia and B-cell chronic lymphocytic leukemia. Cladribine, sold under the brand name Mavenclad, is used for the treatment of adults with highly active forms of relapsing-remitting multiple sclerosis.
In causal inference, a confounder is a variable that influences both the dependent variable and independent variable, causing a spurious association. Confounding is a causal concept, and as such, cannot be described in terms of correlations or associations. The existence of confounders is an important quantitative explanation why correlation does not imply causation. Some notations are explicitly designed to identify the existence, possible existence, or non-existence of confounders in causal relationships between elements of a system.
Dronedarone, sold under the brand name Multaq, is a medication by Sanofi-Aventis, mainly for the indication of cardiac arrhythmias. It was approved by the FDA on July 2, 2009. It was recommended as an alternative to amiodarone for the treatment of atrial fibrillation and atrial flutter in people whose hearts have either returned to normal rhythm or who undergo drug therapy or electric shock treatment i.e. direct current cardioversion (DCCV) to maintain normal rhythm. It is a class III antiarrhythmic drug. In the United States, the FDA approved label includes a claim for reducing hospitalization, but not for reducing mortality, as a reduction in mortality was not demonstrated in the clinical development program. A trial of the drug in heart failure was stopped as an interim analysis showed a possible increase in heart failure deaths, in patients with moderate to severe CHF.
The risk difference (RD), excess risk, or attributable risk is the difference between the risk of an outcome in the exposed group and the unexposed group. It is computed as , where is the incidence in the exposed group, and is the incidence in the unexposed group. If the risk of an outcome is increased by the exposure, the term absolute risk increase (ARI) is used, and computed as . Equivalently, if the risk of an outcome is decreased by the exposure, the term absolute risk reduction (ARR) is used, and computed as .
Medical statistics deals with applications of statistics to medicine and the health sciences, including epidemiology, public health, forensic medicine, and clinical research. Medical statistics has been a recognized branch of statistics in the United Kingdom for more than 40 years but the term has not come into general use in North America, where the wider term 'biostatistics' is more commonly used. However, "biostatistics" more commonly connotes all applications of statistics to biology. Medical statistics is a subdiscipline of statistics. "It is the science of summarizing, collecting, presenting and interpreting data in medical practice, and using them to estimate the magnitude of associations and test hypotheses. It has a central role in medical investigations. It not only provides a way of organizing information on a wider and more formal basis than relying on the exchange of anecdotes and personal experience, but also takes into account the intrinsic variation inherent in most biological processes."
Esketamine, also known as (S)-ketamine or S(+)-ketamine, is the S(+) enantiomer of ketamine, is a dissociative hallucinogen drug used as a general anesthetic and as an antidepressant for treatment of depression. It is sold under the brand names Spravato, Ketanest, among others. Esketamine is the active enantiomer of ketamine in terms of NMDA receptor antagonism and is more potent than racemic ketamine.
Dapagliflozin, sold under the brand names Farxiga (US) and Forxiga (EU) among others, is a medication used to treat type 2 diabetes. It is also used to treat adults with heart failure and chronic kidney disease.
A glossary of terms used in clinical research.
The following outline is provided as an overview of and topical guide to clinical research:
Placebo-controlled studies are a way of testing a medical therapy in which, in addition to a group of subjects that receives the treatment to be evaluated, a separate control group receives a sham "placebo" treatment which is specifically designed to have no real effect. Placebos are most commonly used in blinded trials, where subjects do not know whether they are receiving real or placebo treatment. Often, there is also a further "natural history" group that does not receive any treatment at all.
The JUPITER trial was a clinical trial aimed at evaluating whether statins reduce heart attacks and strokes in people with normal cholesterol levels.
Baricitinib, sold under the brand name Olumiant among others, is an immunomodulatory medication used for the treatment of rheumatoid arthritis, alopecia areata, and COVID-19. It acts as an inhibitor of janus kinase (JAK), blocking the subtypes JAK1 and JAK2.
Sprifermin (INN), is a recombinant human fibroblast growth factor 18 (rhFGF18) analog, which is under development by TrialSpark for the treatment of osteoarthritis. FGF18 and sprifermin act via the Fibroblast Growth Factor Receptor (FGFR) family, with preferential activity via FGFR3c.
Recombinant human parathyroid hormone, sold under the brand names Preotact and Natpara, is an artificially manufactured form of the parathyroid hormone used to treat hypoparathyroidism. Recombinant human parathyroid hormone is used in the treatment of osteoporosis in postmenopausal women at high risk of osteoporotic fractures. A significant reduction in the incidence of vertebral fractures has been demonstrated.