Blood test
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A '''blood test''' is a [[medical laboratory|laboratory]] analysis performed on a [[blood]] sample that is usually extracted from a [[vein]] in the arm using a [[hypodermic needle|needle]], or via [[fingerprick]].
Blood tests are used to determine [[physiological]] and [[biochemical]] states such as [[disease]], [[mineral]] content, drug effectiveness, and organ function. Although the term ''blood test'' is used, most routine tests (except for most [[haematology]]) are done on [[blood plasma|plasma or serum]] instead of blood cells.
==Extraction==
[[Venipuncture]] is useful as it is a relatively [[non-invasive (medical)|non-invasive]] way to obtain [[cell (biology)|cell]]s, and [[extracellular fluid]] ([[blood plasma|plasma]]), from the body for analysis. Since blood flows throughout the body, acting as a medium for providing [[oxygen]] and nutrients, and drawing waste products back to the excretory systems for disposal, the state of the bloodstream affects, or is affected by, many medical conditions. For these reasons, blood tests are the most commonly performed [[medical test]]s.
[[Phlebotomist]]s, laboratory technicians and [[nurse]]s are those charged with patient blood extraction. However, in special circumstances, and emergency situations, [[paramedic]]s and [[physician]]s sometimes extract blood. Also, [[respiratory therapist]]s are trained to extract arterial blood<ref>{{cite journal |author=Aaron SD, Vandemheen KL, Naftel SA, Lewis MJ, Rodger MA |title=Topical tetracaine prior to arterial puncture: a randomized, placebo-controlled clinical trial |journal=Respir Med. |volume=97 |issue=11 |pages=1195–1199 |year=2003 |pmid=14635973 |doi=10.1016/S0954-6111(03)00226-9}}</ref><ref>[http://www.michigan.gov/careers/0,1607,7-170-46398-64537--,00.html http://www.michigan.gov/careers/0,1607,7-170-46398-64537--,00.html]</ref> for [[arterial blood gas]]ses.
==Types of blood tests==
===Biochemical analysis===
A [[basic metabolic panel]] measures [[sodium]], [[potassium]], [[chloride]], [[bicarbonate]], [[blood urea nitrogen]] (BUN), [[magnesium]], [[creatinine]], and [[glucose]]. It also sometimes includes [[calcium]].
Some blood tests, such as measuring [[glucose]], [[cholesterol]], or for [[sexually transmitted disease|STD]] screening require fasting (or no food consumption) eight to twelve hours prior to the blood test.
For the majority of blood tests, blood is usually obtained from the patient's vein. However, other specialized blood tests, such as the [[Arterial blood gas]], require blood extracted from an [[artery]]. Blood gas analysis of arterial blood is primarily used to monitor [[carbon dioxide]] and [[oxygen]] levels related to [[pulmonary]] function. But, it is also used to measure blood [[pH]] and [[bicarbonate]] levels for certain metabolic conditions.
While the regular [[glucose test]] is taken at a certain point in time, the [[glucose tolerance test]] involves repeated testing to determine the rate at which [[glucose]] is processed by the body.
In 2008, scientists announced that saliva tests could eventually replace blood tests, reducing the cost and the unpleasantness of a needle test.<ref>http://www.presstv.ir/detail.aspx?id=49062§ionid=3510210</ref>
====Normal ranges====
{{Main|Reference ranges for common blood tests}}
{| class="wikitable"
|'''Test'''<ref>C. A. Burtis and E. R. Ashwood, ''Tietz Textbook of Clinical Chemistry'' (1994) 2nd edition, ISBN 0-7216-4472-4</ref>||'''Low'''||'''High'''||'''Unit'''||'''Comments'''
|-
| [[Sodium]] (Na) || 136 || 145 || mmol/L ||
|-
| [[Potassium]] (K) || 3.5 || 4.5 || mmol/L ||
|-
| [[Urea]] || 2.5 || 6.4 || mmol/L || BUN - [[blood urea nitrogen]]
|-
| [[Urea]] || 7 || 18 || mg/dL ||
|-
| [[Creatinine]] - male || 62 || 115 || μmol/L ||
|-
| [[Creatinine]] - female || 53 || 97 || μmol/L ||
|-
| [[Creatinine]] - male || 0.7 || 1.3 || mg/dL ||
|-
| [[Creatinine]] - female || 0.6 || 1.1 || mg/dL ||
|-
| [[Glucose]] (fasting) || 3.9 || 5.8 || mmol/L || ''See also'' [[glycosylated hemoglobin]]
|-
| [[Glucose]] (fasting) || 70 || 105 || mg/dL ||
|-
|}
===Molecular profiles===
* [[Protein electrophoresis]] (general technique -- not a specific test)
* [[Western blot]] (general technique -- not a specific test)
* [[Liver function tests]]
* [[Polymerase chain reaction]] (DNA). [[DNA testing]] is today possible with even very small quantities of blood: this is commonly used in [[forensic science]], but is now also part of the diagnostic process of many disorders.
* [[Northern blot]] (RNA)
* [[Sexually transmitted disease]]s
===Cellular evaluation===
* [[Full blood count]] (or "complete blood count")
* [[Hematocrit]] and [[mean corpuscular volume|MCV]] ("mean corpuscular volume")
* [[Erythrocyte sedimentation rate]] (ESR)
* [[Cross-matching]]. Determination of [[blood type]] for [[blood transfusion]] or [[Organ transplant|transplants]]
* [[Blood cultures]] are commonly taken if infection is suspected. Positive cultures and resulting sensitivity results are often useful in guiding medical treatment.
==See also==
* [[Reference ranges for common blood tests]] (with a much longer list)
* [[Urine test]], another common style of body fluid test
* [[Blood film]], a way to look at blood cells under a [[microscope]]
* [[Hematology]], the study of blood
==References==
{{reflist}}
== External links ==
*[http://www.healthatoz.com/healthatoz/Atoz/ency/cold_agglutinins_test.jsp Cold autoantibody webpage on "health a to z"]
{{Abnormal clinical and laboratory findings}}
[[Category:Blood tests]]
[[Category:Medical tests]]
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