A
reference range is usually defined as the set of values 95 percent of the normal population falls within (that is, 95%
prediction interval). It is determined by collecting data from vast numbers of laboratory tests.
Plasma or whole blood In this article, all values (except the ones listed below) denote
blood plasma concentration, which is approximately 60–100% larger than the actual blood concentration if the amount inside
red blood cells (RBCs) is negligible. The precise factor depends on
hematocrit as well as amount inside RBCs. Exceptions are mainly those values that denote total blood concentration, and in this article they are: • All values in
Hematology – red blood cells (except
hemoglobin in plasma) • All values in
Hematology – white blood cells • Platelet count (Plt) A few values are for inside red blood cells only: •
Vitamin B9 (folic acid/folate) in red blood cells • Mean corpuscular hemoglobin concentration (MCHC)
Units •
Mass concentration (g/dL or g/L) is the most common measurement unit in the United States. Is usually given with dL (decilitres) as the denominator in the United States, and usually with L (litres) in, for example, Sweden. •
Molar concentration (mol/L) is used to a higher degree in most of the rest of the world, including the United Kingdom and other parts of Europe and Australia and New Zealand. •
International units (IU) are based on measured
biological activity or effect, or for some substances, a specified equivalent mass. •
Enzyme activity (
kat) is commonly used for e.g.
liver function tests like
AST,
ALT,
LD and
γ-GT in Sweden.
Arterial or venous If not otherwise specified, a reference range for a blood test is generally the
venous range, as the standard process of obtaining a sample is by
venipuncture. An exception is for acid–base and
blood gases, which are generally given for arterial blood. Still, the blood values are approximately equal between the arterial and venous sides for most substances, with the exception of acid–base, blood gases and drugs (used in
therapeutic drug monitoring (TDM) assays). Arterial levels for drugs are generally higher than venous levels because of extraction while passing through tissues. diet, use of prescribed or herbal drugs and stress. Reference ranges often depend on the analytical method used, for reasons such as
inaccuracy, lack of
standardisation, lack of
certified reference material and differing
antibody reactivity. Also, reference ranges may be inaccurate when the reference groups used to establish the ranges are small. ==Sorted by concentration==