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SI Units
International System of Units (SI Units)
Système International d’Unités, 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 concentra- tion, and express whole-unit multiples of three as powers of ten (eg, millimole = 10– 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 pre- ferred. 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 gravimet- ric 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
Abbreviation Definition BCE bone collagen equivalent creat creatinine d day dL deciliter g gram h hour IU international units kat katal (mol/s) L liter mg milligram min minute mL milliliter mL/h milliliter/hour mol mole mmol millimole mIU milli international units ng nanogram pg picogram pmol picomole s second U units μg microgram μmol micromole μU microunits y year
Part 4
Analyte GravimetricUnit ConversionFactor InternationalUnit
ACTH pg/mL 0.22 pmol/L Albumin μg/dL 0.01 mg/L g/dL 10 g/L Aldosterone, S ng/dL 0.0277 nmol/L Aldosterone, U μg/24 h 2.77 nmol/d Alkaline Phosphatase, Bone Specific μg/L 1.0 μg/L Alpha Subunit ng/mL 1.0 μg/L 3 α-Androstanediol Glucuronide ng/dL 0.0213 nmol/L Androstenedione ng/dL 0.0349 nmol/L Angiotensin Converting Enzyme U/L 0.017 μKat/L Angiotensin II ng/L 1.0 ng/L 1,5-Anhydroglucitol (1,5-AG) μg/mL 6.0918 μmol/L Anti-Müllerian Hormone ng/mL 7.1429 pmol/L Apolipoprotein A1 mg/dL 0.01 g/L Apolipoprotein B mg/dL 0.01 g/L Arginine Vasopressin pg/mL 0.926 pmol/L B-Type Natriuretic Peptide pg/mL 1.0 ng/L C-peptide, 24-h U μg/g creat 0.0377 nmol/mmol creat C-Peptide, S ng/mL 0.333 nmol/L Calcitonin pg/mL 1.0 ng/L Calcium, Ionized mg/dL 0.25 mmol/L Calcium, S mg/dL 0.25 mmol/L Calcium, U mg/24 h 0.025 mmol/d mg/g creat 2.828 mmol/mol creat mg/mg creat 2.828 mmol/mmol creat Catecholamines, P Epinephrine pg/mL 5.454 pmol/L Norepinephrine pg/mL 5.914 pmol/L Dopamine pg/mL 6.524 pmol/L Catecholamines, U Epinephrine μg/24 h 5.454 nmol/d Norepinephrine μg/24 h 5.914 nmol/d Dopamine μg/24 h 6.524 nmol/d Epinephrine μg/g creat 0.617 μmol/mol creat Norepinephrine μg/g creat 0.669 μmol/mol creat Dopamine μg/g creat 0.738 μmol/mol creat Cholesterol, HDL mg/dL 0.0259 mmol/L Cholesterol, HDL Subclasses mg/dL 0.0259 mmol/L Cholesterol, LDL, Direct mg/dL 0.0259 mmol/L S, serum; U, urine; P, plasma; ACTH, adrenocorticotropic hormone.
Part 4
Analyte GravimetricUnit ConversionFactor InternationalUnit
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 μg/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 5.23 μmol/d mg/g creat 0.592 μmol/mmol Histamine Plasma or whole blood ng/mL 8.997 nmol/L Urine μg/g creat 1.018 nmol/mmol creat mg/24 h 8.997 μmol/d Homovanillic Acid mg/24 h 5.49 μmol/d mg/g creat 0.621 μmol/mmol creat 17-Hydroxycorticosteroids mg/24 h 2.76 μmol/d mg/g creat 0.312 mmol/mol creat 18-Hydroxycorticosterone ng/dL 0.0276 nmol/L 6 β-Hydroxycortisol μg/24 h 2.642 nmol/d 18-Hydroxycortisol μg/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 μmol/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 μg/L IGFBP-2 ng/mL 1.0 μg/L IGFBP-3 mg/L 1.0 mg/L IGF-I ng/mL 1.0 μg/L IGF-II ng/mL 1.0 μg/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 μIU/mL 7.175 pmol/L Insulin, Total μIU/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.
SI Units
International System of Units (SI Units)
Analyte GravimetricUnit ConversionFactor InternationalUnit 17-Ketosteroids mg/24 h 3.47 μmol/d mg/g creat 0.392 μmol/mmol creat Leptin ng/mL 1.0 μg/L LH (Luteinizing Hormone) mIU/mL 1.0 IU/L Lipoprotein (a) mg/dL 0.01 g/L Macroprolactin ng/mL 1.0 μg/L Magnesium, S mg/dL 0.4114 mmol/L Magnesium, U mg/24 h 0.0411 mmol/d mg/g creat 4.6542 mmol/mol creat Metanephrines, P Metanephrine pg/mL 5.07 pmol/L Normetanephrine pg/mL 5.46 pmol/L Total pg/mL 5.26 pmol/L Metanephrines, U Metanephrine μg/24 h 5.07 nmol/d Normetanephrine μg/24 h 5.46 nmol/d Total μg/24 h 5.26 nmol/d Metanephrine μg/g creat 0.574 nmol/mmol creat Normetanephrine μg/g creat 0.617 nmol/mmol creat Total μg/g creat 0.595 nmol/mmol creat Microalbumin, U mg/24 h 1.0 mg/d μg/min 1.0 μg/min mg/g creat 0.113 mg/mmol creat μg/mg creat 0.113 μg/μmol creat Osmolality, S mOsm/kg 1.0 mmol osmotically active particles/kg H 2 O Osmolality, U mOsm/kg 1.0 mmol osmotically active particles/kg H 2 O Osteocalcin ng/mL 1.0 μg/L ng/dL 0.01 μg/L Pancreatic Polypeptide pg/mL 1.0 ng/L Plasma Renin Activity (PRA) ng/mL/h 1.0 μg/L/h ng/mL/h 0.2778 ng/L•s Prealbumin μg/dL 0.01 mg/L Pregnanetriol μg/24 h 2.97 nmol/d μg/g creat 0.336 μmol/mol creat Pregnenolone ng/dL 0.0316 nmol/L Procollagen Type I Intact N-Terminal μg/L 0.0286 nmol/L Propeptide S, serum; U, urine; P, plasma.
