Units in AMA
Content
AMA manual of style – Key points for Units of Measures The International System of Units is established by international agreement and is the official measurement systems of most nations in the world. Enlisted below are some uniform units of numerical data that are used commonly in medical writingThe 7 basic SI units are – Quantity Base unit name SI unit symbol Length Meter m Mass Kilogram kg Time Second S Electric current Ampere A Thermodynamic Kelvin K temperature Luminous intensity Candela cd Amount of substance Mole mol Capacity/ volume Litre l The structure of other measurement quantities is composed from these base units. For e.g. Derived units Quantity Area Volume Concentration Frequency Force Work, energy Name Square meter Cubic meter Mole per cubic meter Hertz Newton Joule SI symbol m2 m3 mol/ m3 Hz N J Derivation from base unit m2 m3 mol/ m3 s-1 kg.m.s-2 kg.m2.s-2 (N.m)
PREFIXES Multiples of SI units are from prefixes combines with base units and derives unitsPrefix Mega Kilo Deci Centi Milli Micro Femto Factor 106 103 10-1 10-2 10-3 10-6 10-15 Symbol M k d C M µ f
EXPRESSING UNIT NAMES AND SYMBOLS Capitalization: Except degree Celsius (C), all SI units are written in lower case (eg. kg). Also abbreviations from proper names like Kelvin and N for Newton should be capitalized. ‘L’ is used to denote liter to avoid confusion with lower case ‘l’ and the numeral ‘1’.
Product and quotients of unit symbols: The product of 2 or more SI units is indicated by a space or by raised multiplication dot.
Eg. Newton meter is expressed as N m or N · m Eg. When numerals are used, prefer 88 N · m and avoid 88 newton meter The quotient of SI unit maybe expresses by the forward slash or negative components
Eg. µg/L or µg L-1 or µg · L-1 Format style and punctuation: Exponents are preferred in the SI system than certain abbreviations eg. m2 instead of sq m Unit symbols are never expressed in plural forms eg. 1 L and 70 L instead of 70 Ls Unit of measure are treated as collective singular nouns and require singular verb eg. to control the patients fever, 500 mg of acetoaminophen was administered at the time of admission and 1000 mg was required 4 hours later. Most units are abbreviated when used with numerals or with a forward slash.kg m s-2 Symbols or abbreviations never end in a period unless they are at the end of the sentence. Eg. The patient’s weight was 80 kg and further increased by 10%. Hyphen is used to join 2 spelled out units of measure (eg. pascal-second) and when a unit of measure is used as an adjective ( and 8-L container ) Except degree sign (Celsius and angle), and normal and molar solutions, a full space should be given after numerical values of quantity and the unit of measurement. Eg. 140 nmol/L, 135-150nMol/L.
Use of numerals with units: Arabic units are used for quantities with units of measurement. By SI convention, it is preferred to use only numbers between 0.1 to 1000.
Eg. 0.0003 is expressed as 3 µL and 15000 g is expressed as 15 kg. In the decimal format, mumerical values < 1 require placing 0 before the decimal. Eg. 0.1258 and not .123. Exception to this case is certain statistical values such as α levels and P values.
eg. The sample size was based on detecting a 10% difference in the primary outcome measure, using a 2 –sided α level of .05. According to the SI convention, decimal point is the only punctuation mark allowed in numerals, and it is used to separate the integer and decimal parts of the number. Preferred Avoid 1234 1,234 123 456 123,456 12 345.678 901 123,45.678901 1 234 567.8901 1,234,567.8901 Multiplication of numbers should be indicated by the ‘x’ sign. Eg. 15 x 35-cm2
PREFIXES Multiples of SI units are from prefixes combines with base units and derives unitsPrefix Mega Kilo Deci Centi Milli Micro Femto Factor 106 103 10-1 10-2 10-3 10-6 10-15 Symbol M k d C M µ f
EXPRESSING UNIT NAMES AND SYMBOLS Capitalization: Except degree Celsius (C), all SI units are written in lower case (eg. kg). Also abbreviations from proper names like Kelvin and N for Newton should be capitalized. ‘L’ is used to denote liter to avoid confusion with lower case ‘l’ and the numeral ‘1’.
Product and quotients of unit symbols: The product of 2 or more SI units is indicated by a space or by raised multiplication dot.
Eg. Newton meter is expressed as N m or N · m Eg. When numerals are used, prefer 88 N · m and avoid 88 newton meter The quotient of SI unit maybe expresses by the forward slash or negative components
Eg. µg/L or µg L-1 or µg · L-1 Format style and punctuation: Exponents are preferred in the SI system than certain abbreviations eg. m2 instead of sq m Unit symbols are never expressed in plural forms eg. 1 L and 70 L instead of 70 Ls Unit of measure are treated as collective singular nouns and require singular verb eg. to control the patients fever, 500 mg of acetoaminophen was administered at the time of admission and 1000 mg was required 4 hours later. Most units are abbreviated when used with numerals or with a forward slash.kg m s-2 Symbols or abbreviations never end in a period unless they are at the end of the sentence. Eg. The patient’s weight was 80 kg and further increased by 10%. Hyphen is used to join 2 spelled out units of measure (eg. pascal-second) and when a unit of measure is used as an adjective ( and 8-L container ) Except degree sign (Celsius and angle), and normal and molar solutions, a full space should be given after numerical values of quantity and the unit of measurement. Eg. 140 nmol/L, 135-150nMol/L.
Use of numerals with units: Arabic units are used for quantities with units of measurement. By SI convention, it is preferred to use only numbers between 0.1 to 1000.
Eg. 0.0003 is expressed as 3 µL and 15000 g is expressed as 15 kg. In the decimal format, mumerical values < 1 require placing 0 before the decimal. Eg. 0.1258 and not .123. Exception to this case is certain statistical values such as α levels and P values.
eg. The sample size was based on detecting a 10% difference in the primary outcome measure, using a 2 –sided α level of .05. According to the SI convention, decimal point is the only punctuation mark allowed in numerals, and it is used to separate the integer and decimal parts of the number. Preferred Avoid 1234 1,234 123 456 123,456 12 345.678 901 123,45.678901 1 234 567.8901 1,234,567.8901 Multiplication of numbers should be indicated by the ‘x’ sign. Eg. 15 x 35-cm2
