International System of Units (SI Units)

International System of Units (SI Units)

Syst?me International d'Unit?s, or SI units, are an extension of the meter, kilogram, second, ampere (MKSA) system proposed in 1950. In 1966, the International Federation of Clinical Chemistry (IFCC) recommended the use of selected, or favored, SI units for the clinical laboratory: whenever possible, use mole and liter units to express concentration, and express whole-unit multiples of three as powers of ten (eg, millimole = 10?3 moles, micromole = 10?6 moles, nanomole = 10?9 moles, picomole = 10?12 moles). This approach was designed to provide clearer quantitative relationships among molecular species and some standardization of databases.

This partial application of SI units to laboratory data has been accepted by many scientific journals and is used increasingly in day-to-day clinical medicine. The operative words are "whenever possible." In many instances the molecular weight or the homogeneity of the measured analyte is not clear, and gravimetric units rather than molar units are preferred.

With regard to laboratory reports, we remain in a transition state between conventional (gravimetric) units and SI units. Quest Diagnostics is moving to SI units but continues to use selected conventional units during what has become a prolonged transition period. For your convenience, we have included a guide for interconversion of conventional and SI units, along with definitions of abbreviations used. The following table lists gravimetric and possible international unitage for a variety of laboratory tests. The conversion factor (CF) is used as follows:

gravimetric ? CF = international unit international ? CF = gravimetric unit

SI Units

Abbreviation

BCE creat d dL g h IU kat L mg min mL mL/h mol mmol mIU ng pg pmol s U ?g ?mol ?U y

Definition

bone collagen equivalent creatinine day deciliter gram hour international units katal (mol/s) liter milligram minute milliliter milliliter/hour mole millimole milli international units nanogram picogram picomole second units microgram micromole microunits year

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Part 4

Analyte

Gravimetric Conversion

Unit

Factor

ACTH

pg/mL

0.22

Albumin

?g/dL

0.01

g/dL

10

Aldosterone, S

ng/dL

0.0277

Aldosterone, U

?g/24 h

2.77

Alkaline Phosphatase, Bone Specific ?g/L

1.0

Alpha Subunit

ng/mL

1.0

3-Androstanediol Glucuronide

ng/dL

0.0213

Androstenedione

ng/dL

0.0349

Angiotensin Converting Enzyme U/L

0.017

Angiotensin II

ng/L

1.0

1,5-Anhydroglucitol (1,5-AG)

?g/mL

6.0918

Anti-M?llerian Hormone

ng/mL

7.1429

Apolipoprotein A1

mg/dL

0.01

Apolipoprotein B

mg/dL

0.01

Arginine Vasopressin

pg/mL

0.926

B-Type Natriuretic Peptide

pg/mL

1.0

C-peptide, 24-h U

?g/g creat 0.0377

C-Peptide, S

ng/mL

0.333

Calcitonin

pg/mL

1.0

Calcium, Ionized

mg/dL

0.25

Calcium, S

mg/dL

0.25

Calcium, U

mg/24 h

0.025

mg/g creat 2.828

mg/mg creat 2.828

Catecholamines, P Epinephrine Norepinephrine Dopamine

pg/mL pg/mL pg/mL

5.454 5.914 6.524

Catecholamines, U Epinephrine Norepinephrine Dopamine

?g/24 h ?g/24 h ?g/24 h

5.454 5.914 6.524

Epinephrine Norepinephrine Dopamine

?g/g creat ?g/g creat ?g/g creat

0.617 0.669 0.738

Cholesterol, HDL

mg/dL

0.0259

Cholesterol, HDL Subclasses

mg/dL

0.0259

Cholesterol, LDL, Direct

mg/dL

0.0259

S, serum; U, urine; P, plasma; ACTH, adrenocorticotropic hormone.

International Unit pmol/L mg/L g/L nmol/L nmol/d ?g/L ?g/L nmol/L nmol/L ?Kat/L ng/L ?mol/L pmol/L g/L g/L pmol/L ng/L nmol/mmol creat nmol/L ng/L mmol/L mmol/L mmol/d mmol/mol creat mmol/mmol creat

pmol/L pmol/L pmol/L

nmol/d nmol/d nmol/d ?mol/mol creat ?mol/mol creat ?mol/mol creat mmol/L mmol/L mmol/L

340

International System of Units (SI Units)

Analyte

Gravimetric Conversion International

Unit

Factor

Unit

Cholesterol, Total

mg/dL

0.0259

mmol/L

Chromogranin A

ng/mL

1.0

?g/L

Collagen Cross-Linked N-Telopeptide (NTx)

nmol BCE/ 1.0 mmol creat

nmol BCE/ mmol creat

Collagen Type 1 C-Telopeptide (CTx) pg/mL

1.0

ng/L

Corticosterone

ng/dL

0.0289

nmol/L

Corticotropin Releasing Hormone pg/mL

1.0

ng/L

Cortisol Binding Globulin

mg/L

17.18

nmol/L

Cortisol, Free, S

?g/dL

27.6

nmol/L

Cortisol, Free, U

?g/24 h ?g/g creat

2.76 0.3122

nmol/d ?mol/mol creat

Cortisol, S and Saliva

?g/dL

27.6

nmol/L

Cortisone, S

?g/dL

0.0277

?mol/L

Cortisone, U

?g/24 h

2.774

mmol/d

Creatinine

mg/dL

88.4

g/24 h

8.84

?mol/L mmol/d

Cyclic AMP, Urine

nmol/mL

1.0

?mol/L

Cystatin C

mg/L

1.0

mg/L

Deoxycorticosterone

ng/dL

0.0303

nmol/L

11-Deoxycortisol

ng/dL

0.0289

nmol/L

Dexamethasone

ng/dL

25.48

pmol/L

DHEA

ng/dL ?g/24 h ?g/g creat

0.0347 0.0035 0.3922

nmol/L ?mol/d ?mol/mol creat

DHEA Sulfate

?g/dL

0.0271

?mol/L

Dihydrotestosterone

ng/dL

0.0344

nmol/L

Dihydrotestosterone, Free

pg/mL

3.440

pmol/L

Estradiol (E2), Free Estradiol (E2), S Estrogen, Total, S

pg/mL

3.67

pg/mL

3.67

pg/mL

1.0

pmol/L pmol/L ng/L

Estrogens, Fractionated, S Estrone Estradiol Estriol

pg/mL pg/mL ng/mL

3.699 3.67 3.47

pmol/L pmol/L nmol/L

Estrone (E1), S Estrone Sulfate

pg/mL pg/mL

3.699 2.730

pmol/L pmol/L

Fructosamine

?mol/L

1.0

?mol/L

FSH

mIU/mL

1.0

IU/L

S, serum; U, urine; P, plasma; DHEA, dehydroepiandrosterone; FSH, follicle stimulating hormone.

SI Units

341

Part 4

Analyte

Gravimetric Conversion International

Unit

Factor

Unit

GAD-65 Antibodies

U/mL

1.0

kU/L

Gastrin

pg/mL

1.0

ng/L

Glucagon

pg/mL

1.0

ng/L

Glucose, S

mg/dL

0.0555

mmol/L

Growth Hormone

ng/mL

1.0

?g/L

Growth Hormone Binding Protein pmol/L

1.0

pmol/L

hCG, Beta Subunit

mIU/mL

1.0

IU/L

hCG, Total

mIU/mL

1.0

IU/L

5-HIAA

mg/24 h mg/g creat

5.23 0.592

?mol/d ?mol/mmol

Histamine Plasma or whole blood Urine

ng/mL ?g/g creat mg/24 h

8.997 1.018 8.997

nmol/L nmol/mmol creat ?mol/d

Homovanillic Acid

mg/24 h mg/g creat

5.49 0.621

?mol/d ?mol/mmol creat

17-Hydroxycorticosteroids

mg/24 h mg/g creat

2.76 0.312

?mol/d mmol/mol creat

18-Hydroxycorticosterone

ng/dL

0.0276

nmol/L

6-Hydroxycortisol

?g/24 h

2.642

nmol/d

18-Hydroxycortisol

?g/24 h

2.642

nmol/d

21-Hydroxylase Antibody

U/mL

1.0

kU/L

17-Hydroxypregnenolone

ng/dL

0.0301

nmol/L

17-Hydroxyprogesterone

ng/dL

0.0303

nmol/L

Hydroxyproline

mg/dL

76.3

?mol/L

Hyperglycosylated hCG (h-hCG) pg/mL

0.0255

pmol/L

IA-2 Antibody

U/mL

1.0

kU/L

IGFBP-1

ng/mL

1.0

?g/L

IGFBP-2

ng/mL

1.0

?g/L

IGFBP-3

mg/L

1.0

mg/L

IGF-I

ng/mL

1.0

?g/L

IGF-II

ng/mL

1.0

?g/L

Inhibin A

pg/mL

1.0

ng/L

Inhibin B

pg/mL

1.0

ng/L

Insulin Antibodies

U/mL

1.0

kU/L

Insulin, Free

?IU/mL

7.175

pmol/L

Insulin, Total

?IU/mL

7.175

pmol/L

S, serum; U, urine; P, plasma; GAD-65, glutamic acid decarboxylase-65; hCG, human chorionic gonadotropin; 5-HIAA, 5-hydroxyindoleacetic acid; IGFBP, IGF binding protein; IGF, insulin-like growth factor.

342

International System of Units (SI Units)

Analyte

17-Ketosteroids

Leptin LH (Luteinizing Hormone) Lipoprotein (a) Macroprolactin Magnesium, S Magnesium, U

Metanephrines, P Metanephrine Normetanephrine Total

Metanephrines, U Metanephrine Normetanephrine Total Metanephrine Normetanephrine Total

Microalbumin, U

Osmolality, S

Gravimetric Unit mg/24 h mg/g creat ng/mL mIU/mL mg/dL ng/mL mg/dL mg/24 h mg/g creat

pg/mL pg/mL pg/mL

?g/24 h ?g/24 h ?g/24 h ?g/g creat ?g/g creat ?g/g creat mg/24 h ?g/min mg/g creat ?g/mg creat mOsm/kg

Osmolality, U

mOsm/kg

Osteocalcin

ng/mL ng/dL

Pancreatic Polypeptide

pg/mL

Plasma Renin Activity (PRA)

ng/mL/h ng/mL/h

Prealbumin

?g/dL

Pregnanetriol

?g/24 h ?g/g creat

Pregnenolone

ng/dL

Procollagen Type I Intact N-Terminal ?g/L Propeptide

S, serum; U, urine; P, plasma.

Conversion Factor 3.47 0.392 1.0 1.0 0.01 1.0 0.4114 0.0411 4.6542

International Unit ?mol/d ?mol/mmol creat ?g/L IU/L g/L ?g/L mmol/L mmol/d mmol/mol creat

5.07

pmol/L

5.46

pmol/L

5.26

pmol/L

5.07 5.46 5.26 0.574 0.617 0.595 1.0 1.0 0.113 0.113 1.0

1.0

1.0 0.01 1.0 1.0 0.2778 0.01 2.97 0.336 0.0316 0.0286

nmol/d nmol/d nmol/d

nmol/mmol creat nmol/mmol creat nmol/mmol creat

mg/d ?g/min mg/mmol creat ?g/?mol creat

mmol osmotically active particles/kg H2O mmol osmotically active particles/kg H2O ?g/L ?g/L

ng/L

?g/L/h ng/L?s

mg/L

nmol/d ?mol/mol creat

nmol/L

nmol/L

SI Units

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