efficacy

Efficacy is the capacity to produce an effect. It is used to mean different specific things in different fields.

Context

Healthcare

In a healthcare context, efficacy indicates the capacity for beneficial change (or therapeutic effect) of a given intervention (e.g. a medicine, medical device, surgical procedure, or a public health intervention).

If efficacy is established, an intervention is likely to be at least as good as other available interventions, to which it will have been compared. Comparisons of this type are typically made in 'explanatory' randomized controlled trials, whereas 'pragmatic' trials are used to establish the effectiveness of an intervention.

The concept of 'self-efficacy' is an important one in the self-management of chronic diseases because doctors and patients often do not follow best practice in using a treatment. For instance, a patient using combined oral contraceptive pills to prevent pregnancy may sometimes forget to take a pill at the prescribed time; thus, while the perfect-use failure rate for this form of contraception in the first year of use is just 0.3%, the typical-use failure rate is 8%.[1]

Pharmacology

In pharmacology, efficacy, or intrinsic activity, refers to the ability of a drug-receptor complex to produce a functional response.

Lighting

In lighting design, "efficacy" refers to the amount of light (luminous flux) produced by a lamp (a light bulb or other light source), usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts. This is not to be confused with efficiency which is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible power as a fraction of the power consumed in watts. The visible power can be approximated by the area under the Planck curve between 300 nm and 700 nm for a blackbody at the temperature of the filament as a ratio of the total power under the blackbody curve. Efficiency values for light from a heat source are typically less than two percent.

Difference amplifiers

The efficacy of a differential amplifier is measured by the degree of its rejection of common-mode signals in preference to differential signals. Referred to as common-mode rejection ratio (CMRR); typically specified in decibels.

See also

Look up efficacy in Wiktionary, the free dictionary.

• Placebo (origins of technical term)
• Vaccine efficacy
• Efficiency
• Figure of merit
• Self-efficacy
• Effectiveness

References

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