Unit. Symbol plementary units, steradian and metre m radian, are not of concern in kilogram kg medicine. second s mein. Prefixes are used to denote mul- mole.
SI Units in Veterinary Medicine J.H. Lumsden* The metric system has been legal in Canada since the Weights and Measures Act of 1873. The SI unit system (Systeme International d'Unites) is an expanded version of the metric system. In 1970 the White Paper on Metric Conversion in Canada proposing the adoption of the SI unit system was unanimously endorsed by Parliament. Metric units are used by approximately 98% of the world's population. The International System of Units (SI) replaces the Imperial systems and all former versions of the metric system. The initial 1978 target date for conversion suggested by Metric Commission Canada Sector 9.10 Health and Welfare was rescheduled to November 1981 at a joint meeting of Provincial health representatives and spokespersons for the health related professions held in Winnipeg, March, 1981. Veterinary services are included under the Agriculture sector at the Federal and Provincial levels. There have been no specific guidelines received from the Metric Commission Canada regarding introduction of SI units into veterinary medicine. The introduction of SI units into medicine and the scientific literature (2,3) indicates the goal for veterinary medicine. Veterinary teaching institutions, diagnostic and research laboratories have the opportunity to coordinate the introduction of the SI unit system in Canada. In July 1981, the Canadian Association of Veterinary Pathologists agreed upon a suggested conversion date of June, 1982. The editors of the Canadian Veterinary Journal and the Canadian Journal of Comparative Medicine have adopted SI nomenclature (3). This paper is presented as an introduction to the SI unit system. The "SI Manual in Health Care" (2) and "How to write SI units" (1) are
Base Unit metre
SI Symbol m
kilogram second
kg s
mole
kelvin
ampere
mol K A
the international committee as either base or derived units called supplementary units. These supplementary units, steradian and radian, are not of concern in medicine. mein. Prefixes are used to denote multiples or submultiples of SI units, of ten with those factors preferably which are multiples of exponents three as in parts (a) and (c) (Table
candela
cd
II).
Table I. Physical Quantity Length Mass Time Amount of substance Thermodynamic temperature Electrical current Luminous intensity
available through the national and provincial metric ation offices. The use of SI inlternationally will reduce confusion by providing a coherent system of units with quantities and un its presented in a uniform concept and style. The SI has three types of units a) base units b) derived lunits and c) supplementary units . There are seven "base units" whic h in appropriate combinations c an be used to express any ph,ysical quantity (Table I). DerivecI units are a variation of these basEa units. There are certain units not yet classified by * HealthRelated Some SI Units Usedl in in Health Related
Fields
SI Uniits Symbol km kilometre m metre cm centimetre mm (10-3m) millimetre micrometre Mm (10-6m) surface area square cm2 centimeter square metre m2 mass kg kilogram g gram mg milligram microgram ,ug temperature degree Celsius 0 C d day time h hour minute min s second L litre volume mL millilitre substance mol/ L mole/litre
Quantity length
concentration
International symbols are used to denote SI units. The following rules are followed in writing symbols and numbers (ref, Appendix IV). Symbols are always printed in upright type. Lower case is used except when the symbol is derived from a proper name, e.g. g for gram but A for ampere. The one exception to this rule is L for litre. If the full name is used only Celsius takes a capital. There is no space between the prefix and a symbol, e.g. kg for kilogram. Symbols are not pluralized (e.g. 15 kg, not 15 kgs.) Symbols and names should not be mixed. A full space is used between a numeral and the symbol (e.g. 15 g) except when the first character of a symbol is not a letter (e.g. 32°C). If numerals are not Table II. Factor a) 1018 1O'5 1012 109 106 103 b) 102 101
10'
10-2
c) 10-,
10-6
10-9
10-12
10-'5
Prefix exa
peta tera
giga mega kilo* hecto deca deci centi milli* micro* nano* pico femto
Symbol E P T G K k h da d c
m
MA n p
f
a atto 108 *Most frequently used in medicine
*Ontario Veterinary College, University of Guelph, Guelph, Ontario NlG 2W1.
Can. J. comp. Med. 46: 103-104 (January 1982)
103
or to convert from the present pH scale to nanomoles per litre for hydrogen ion concentration. Recommendations have been made for educational procedures to precede introduction of SI units. Many of these are based upon the experience gained in several countries during the past decade.
SI Units in Hematology
Component Hemaglobin RBC PCV MCV MCH MCHC WBC Platelets Red cell diameter Reticulocytes
Present Unit with example 12 g/100 ml 5.5 x 1006/hd
40m/100m1(%)
60 um3/red cell 20 pg/red cell 32 gm/100 ml(%) 7.3 x 103/lA 250 x 103/pl 6.7 jAm 50 x 103/Ml
SI Units in Microbiology Bacterial colony counts #/ml Antibiotic concentration ,g/ml
used the unit name should be written out. The product of two or more units in symbolic form is indicated by a raised dot, e.g. mL.h. A symbol is never followed by a period except at the end of a sentence. When writing numbers use decimals not fractions. The decimal marker is a point in the English language and a comma in the French language. If the unit is less than one use a zero in front of the decimal, e.g. 0.15 g. Long numbers are divided into blocks of three digits with respect to the decimal marker, eg. 52 453.139 6. Spacing is optional with a four digit number, e.g. 1 234 or 1234. The unit of temperature is degree Celsius (not degree centigrade) as the unit kelvin has limited application in medicine. The major change of interest to clinicians is the use of mole to express concentration of those substances with known relative molecular weight (mmol/L). If the molecular mass is unknown the unit for measurement of concentration will be grams or milligrams per litre (g/L, mg/L). Milliequivalents per litre converts to millimoles per litre without a numerical change if the valency of the ion is not greater than one. There are additional derived units currently under study. The SI units of radiation are scheduled for initial introduction in the health sciences in 1982 with full operation by 1984. There are no immediate plans to introduce pascals for measurements of pressure 104
SI Unit with example 120 g/L 5.5 x 1012/L 0.40 L/L 60fl 20 pg 320 g/L 7.5 x 109/L 250 x 109/L 6.7 ,um 50 x 109/L
Significani
digits xxx X.x o.xx xx xx xxx x.x xxx x.x xx
REFERENCES 1. How to Write SI. Metric Commission Canada. Fifth edition. 1978. 2. The SI Manual in Health Care. Metric Commission Canada. 1981. 3. Uniform requirements for manuscripts submitted to biomedical journals. The Lancet 1: 428-431. 1979.
#/L mg/L
SI Units in Clinical Chemistry Component Alanine aminotransferase (SALT or SGPT) Albumin Ammonia (NH3) Amylase Aspartate aminotransferase (SAST or SGOT) Bilirubin Calcium Carbon dioxide Chloride Cholesterol Copper Cortisol Creatine Kinase (CPK) Creatinine Fibrinogen Glucose Iron Lactate Lipase Sigma Tietz (37°C) Cherry Crandall (300C) Lipids, total Magnesium Mercury Osmolality Phosphatase, alkaline Phosphate (as Phosphorus), inorganic Potassium Protein, total Sodium Testosterone Thyroxine (T4) Urea nitrogen
Urobilinogen D-Xylose Zinc
Present Units (with examples)
Conversion factor
SI Unit (with examples)
0-40 U/I
1.00
0-40 U/L
2.8-4.0 g/100 ml 10-8- ,/100 ml 200-800 U/I
1.00 0.5871 1.00
28-40 g/L 5-50 Mmol/L 200-800 U/L
0-40 U/l
1.00
0-40 U/L
Significant Digits xx
xx xxx xxx xx
0.1-0.2 mg/100 ml 8.8-10.3 mg/100 ml 22-28 mEq/l 95-105 mEq/l 100-265 mg/100 ml 70-140,ug/100 ml 2-10Ag/i00 ml
17.10 0.2495 1.00 1.00 0.02586 0.1574 27.59
xx 2-4 ,umol/L 2.20-2.58 mmol/L x.xx xx 22-28 mmol/L 95-105 mmol/L xxx 2.58-5.85 mmol/L x.xx 11.0-22.0 Mmol/L xx.x xxo 55-280 nmol/L
0-130 U/l 0.6-1.2 mg/100 ml 200-400 mg/100 ml 70-110 mg/100 ml 80-180 lg/lOO ml 5-20 mg/100 ml
1.00 88.40 0.01 0.05551 0.1791 0.1110
0-130 U/L mol/L 50-110 l 2.0-4.0 g/L 3.9-61. mmol/L
< 1 ST U/100 ml
0-160 U/l 400-850 mg/100 ml 1.8-3.0 mg/100 ml < 1.0 ,ug/i00 ml 280-330 mOsm/kg
30-150 i/l
280 1.00 0.01 0.4114 49.85 1.00
1.00
2.5-5.0 mg/100 ml 3.5-5.0 mEq/l 5-8 g/100 ml 135-147 mEq/l 4.0-8.0 mg/ml 1-4 Mg/lOO ml 10-20 mg/100 ml
0.3229 1.0 10.0 1.00 3.467 12.87 0.3570
0-4.0 mg/24 h 30-40 mg/100 ml 75-120 Mg/100 ml
1.693 0.0666 0.1530
0.5-2.0 mmol/L
xxx xxo x.x xx.x xx x.x
