Arbitrary pressure ( - Dynamic NPU Manual

Arbitrary pressure (


Chemical amount


Definition in words

Arbitrary pressure of component B in system 1

Definition by equation

Result type

Rational scale
  • Value sets are positive numerical values
  • Numerical values from 0-∞
  • Algebraic operations are allowed
  • Possible comparison of values (a=nb; a≠nb)


International unit (IU) or procedure defined unit (p.d.u.) (non-SI units)

Special rule(s) in the NPU syntax

“Procedure” is stated in the specification to the kind-of-property in the NPU definition.

“Procedure” indicates that the measurement procedure must be stated somewhere else than the NPU code and there may be difficulties in comparing values for the same NPU code.

If the unit is an International Unit (IU), an international certified reference material (e.g. WHO reference material) is specified in the specification to the kind-of-property.

If there exist no international certified reference material, the laboratory can specify the unit at the placeholder, procedure defined unit.


Ferard G, Dybkaer R, Fuentes-Arderiu X. Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences : Recommendations 2016. 1 ed: Royal Society of Chemistry; 2016. 182 p. doi:10.1039/9781782622451.

Laboratory field


Clinical Chemistry

Generic abbreviated form NPU02966 Ercs(B)—Osmotic pressure reaction; Hb/all Hb = 0,5; 37 °C; pH = 7,40; 0 h; proc.) = 0 (p.d.u.)
Full form with a result NPU02966 Erythrocytes(Blood)—Osmotic pressure reaction; arbitrary pressure(Free Hb/all Hb = 0,5; 37 °C; pH = 7.40; 0 h; proc.) = 0 arbitrary unit
Abbreviated form with a result NPU02966 Ercs(B)—Osmotic pressure reaction; Hb/all Hb = 0,5; 37 °C; pH = 7,40; 0 h; proc.) = 0 arbitrary unit
Written expression The arbitrary pressure of Osmotic pressure reaction of erythrocytes in Mr. Smith’s blood is [0] arbitrary unit. The measurement procedure is performed at free Hb/all Hb = 0,5; 37 °C; pH = 7,40; 0 h according to a procedure defined by the laboratory .

“Arbitrary unit” was chosen by a local laboratory as a proprietary measurement unit and not an accepted international units.


NPU database, and


  • Kind-of-property

    • Nominal kind-of-property

    • Kind-of-quantity

      • Unitary kind-of-quantity

        • Rational unitary kind-of-quantity

          • Arbitrary pressure


  • Dybkaer R. Concept system on ‘quantity’: formation and terminology. Accredit Qual Assur. 2013;18(3):253-60.
  • Dybkaer R. ISO terminological analysis of the VIM3 concepts ‘quantity’ and ‘kind-of-quantity’. Metrologia. 2010;47(3):127-34.
Date Term Note
1996-01-01 Arbitrary pressure Term established