|DotNet Class HL7Connect.Cda.PQ|
A dimensioned quantity expressing the result of measuring
|the number which is multiplied by the unit to make the PQ or PQR value if not nullFlavored|
|The reason that this PQ or PQR was provided. More than one reason may be given. For possible values, see 188.8.131.52.10 CD.codingRationale.
Coding Rationale for why a code is provided (CD and PQ/PQR)
|The unit of measure specified in the Unified Code for Units of Measure (UCUM). |
UCUM defines two forms of expression, case sensitive and case insensitive. PQ uses the case sensitive codes. The codeSystem OID for the case sensitive form is 2.16.840.1.113883.6.8. The default value for unit is the UCUM code "1" (unity).
Equality of physical quantities does not require the values and units to be equal independently. Value and unit is only how we represent physical quantities. For example, 1 m equals 100 cm. Although the units are different and the values are different, the physical quantities are equal. Therefore one should never expect a particular unit for a physical quantity but instead allow for automated conversion between different comparable units.
The unit SHALL come from UCUM, which only specifies unambiguous measurement units. Sometimes it is not clear how some measurements in healthcare map to UCUM codes.
Note: The general pattern for a measurement is value unit of Thing. In this scheme, the PQ represents the value and the unit, and the Thing is described by some coded concept that is linked to the PQ by the context of use. This maps obviously to some measurements, such as Patient Body Temperature of 37 Celsius, and 250 mg/day of Salicylate.
However for some measurements that arise in healthcare, the scheme is not so obvious. Two classic examples are 5 Drinks of Beer, and 3 Acetominophen tablets. At first glance it is tempting to classify these measurments like this: 5 drinks of Beer and 3 Acetominophen tablets. The problem with this is that UCUM does not support units of "beer", "tablets" or "scoops".
The reason for this is that neither tablets or scoops are proper units. What kind of tablets? How big is the glass? In these kinds of cases, the concept that appears to be a unit needs to further specified before interoperability is established. If a correct amount is required, then it is generally appropriate to specify an exact measurement with an appropriate UCUM unit. If this is not possible, then the concept is not part of the measurement. UCUM provides a unit called unity for use in these cases. The proper way to understand these measurements as 3 1 Acetominophen tablets, where 1 is the UCUM unit for unity, and the Thing has a qualifier. The context of use will need to provide the extra qualifying information.
|An alternative representation of the same physical quantity expressed in a different unit from a different unit code system and possibly with a different value.|
It is not necessary for information processing entities to check and enforce that the translations are valid translations of the base unit, but they are allowed to do so, and to reject instances where the translations are not valid.
Note Translations are allowed to contain other representations in UCUM units, but there is generally no point to this as it's possible to convert from UCUM form to another.
|The canonical form for the PQ (canonical UCUM units with appropriate conversion)|
|HL7Connect.Cda.BL comparable(HL7Connect.Cda.QTY other);|
|whether other is a PQ and has the same canonical units|