Editing Reference range (section)

{{Short description|Measured values that are relatively normal for a particular medical test}}
{{Reference ranges}}
In [[medicine]] and [[health]]-related fields, a '''reference range''' or '''reference interval''' is the [[range (statistics)|range]] or the [[interval (mathematics)|interval]] of values that is deemed normal for a [[physiology|physiological]] measurement in healthy persons (for example, the amount of [[creatinine]] in the [[blood]], or the [[blood gas tension|partial pressure of oxygen]]). It is a basis for comparison for a [[physician]] or other [[health professional]] to interpret a set of test results for a particular patient. Some important reference ranges in medicine are [[reference ranges for blood tests]] and [[Urinalysis#Target parameters|reference ranges for urine tests]].

The standard definition of a reference range (usually referred to if not otherwise specified) originates in what is most prevalent in a [[reference group]] taken from the general (i.e. total) population. This is the general reference range. However, there are also ''optimal health ranges'' (ranges that appear to have the optimal health impact) and ranges for particular conditions or statuses (such as pregnancy reference ranges for hormone levels).

Values '''within the reference range''' ('''WRR''') are those '''within normal limits''' ('''WNL'''). The limits are called the ''upper reference limit'' (URL) or ''upper limit of normal'' (ULN) and the ''lower reference limit'' (LRL) or ''lower limit of normal'' (LLN). In [[health care]]–related publishing, [[style guide|style sheets]] sometimes prefer the word ''reference'' over the word ''normal'' to prevent the nontechnical [[word sense|senses]] of ''normal'' from being conflated with the statistical sense. Values outside a reference range are not [[wikt:in and of itself#Adverb|necessarily]] pathologic, and they are not necessarily abnormal in any sense other than statistically. Nonetheless, they are indicators of probable pathosis. Sometimes the underlying cause is obvious; in other cases, challenging [[differential diagnosis]] is required to determine what is wrong and thus how to treat it.

A '''cutoff''' or '''threshold''' is a limit used for [[binary classification]], mainly between normal versus pathological (or probably pathological). Establishment methods for cutoffs include using an upper or a lower limit of a reference range.