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In health-related fields, a reference range is a set of values of some measurement that a physician or other health professional can use to interpret a set of results for a particular patient. A physician is a person who practices medicine. ...
The delivery of modern health care depends on an expanding group of highly trained professionals coming together as an interdisciplinary team. ...
It is commonly referred to as the normal range or normal values. This term should be discouraged as not everyone outside the range is abnormal, and people who have a particular condition may still fall within this range.
A reference range for a particular test or measurement, is usually defined as the values that 95% (or 2 standard deviations) of the population fall into. It relies on the fact that for many biological phenomena, there is a normal distribution of values. In probability and statistics, the standard deviation is the most commonly used measure of statistical dispersion. ...
The normal distribution, also called Gaussian distribution, is an extremely important probability distribution in many fields, especially in physics and engineering. ...
For some types of investigations, there may not be a normal distribution. There could be a bimodal distribution, often caused by difference values in males and females. Or it may change with age, (such as prostate specific antigen). There may also be another distribution such as log-normal distribution, where a mathematical function can be applied to correct it. Prostate specific antigen (PSA) is a protein manufactured exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm to swim freely. ...
A good test (or measurement) in the diagnosis of a disease will have a clear distinction between the ranges for normal and the ranges for diseased individuals. A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. ...
A graphical illustration of reference ranges
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 Image File history File links bellcurve with 95% marked on it as a demonstration of simple reference range (made with excel and flash) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
| In an ideal situation, where the distribution is normal, the reference range can be obtained by simply measuring a population and taking two standard deviations either side of the mean. | |
 Image File history File links another excel/flash creation, it might need tweaking File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
| If a normal population shows a bimodal distribution, it is useful to find out why this is the case. Two reference ranges can be established for the two different groups of people. (This pattern is commonly seen in tests that differ between men and women, but could conceivably be seen in a bicultural society and other situations.) In statistics, a bimodal distribution is a distribution with two different peaks — that is, there are two distinct values that measurements tend to center around. ...
| See also: A reference range is a set of values used by a health professional to interpret a set of medical test results. ...
Reference value is a term used in medicine to denote a laboratory value used as a reference for values obtained by laboratory examinations of patients or samples (blood, urine or other materials) collected from patients. ...
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