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A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a 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 plasma or serum, instead of blood cells.

Contents

Extraction

Venipuncture is useful as it is a relatively non-invasive way to obtain cells and extracellular fluid (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 tests.

Phlebotomists, laboratory technicians and nurses are those charged with patient blood extraction. However, in special circumstances, and emergency situations, paramedics and physicians sometimes extract blood. Also, respiratory therapists are trained to extract arterial blood[1][2] for arterial blood gases.

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 those that measure glucose, cholesterol, or for determining the existence or lack of STD, require fasting (or no food consumption) eight to twelve hours prior to the drawing of the blood sample.

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.

Normal ranges

Test[3]LowHighUnitComments
Sodium (Na) 136 145 mmol/L
Potassium (K) 3.5 5.5 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

Cellular evaluation

Future alternatives

In 2008, scientists announced that the more cost effective saliva tests could eventually replace some blood tests, as saliva contains 20% of the proteins found in blood. [4]

See also

References

  1. ^ Aaron SD, Vandemheen KL, Naftel SA, Lewis MJ, Rodger MA (2003). "Topical tetracaine prior to arterial puncture: a randomized, placebo-controlled clinical trial". Respir Med. 97 (11): 1195–1199. doi:10.1016/S0954-6111(03)00226-9. PMID 14635973. 
  2. ^ http://www.michigan.gov/careers/0,1607,7-170-46398-64537--,00.html
  3. ^ C. A. Burtis and E. R. Ashwood, Tietz Textbook of Clinical Chemistry (1994) 2nd edition, ISBN 0-7216-4472-4
  4. ^ Press TV - Saliva test to substitute blood test

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

English

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Wikipedia

Noun

Singular
blood test

Plural
blood tests

blood test (plural blood tests)

  1. A serologic analysis of a sample of blood.

Translations








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