Arbitrary substance ratio (arb.subst.ratio) - Dynamic NPU Manual

Arbitrary substance ratio (arb.subst.ratio)



Definition in words

Arbitrary substance ratio of component B in system 1

Definition by equation

Note 1: Component B is the quotient of component F and component G

Note 2: Component F ≠ Component G (≠ = “not equal to”)

Note 3: Component F ∉ Component G (∉ = “is not an element of”)

Result type

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


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 NPU53987 P—Aldosterone/renin; arb.subst.ratio(IRP 68/356; proc.) = ? nmol/IU
Full form with a result NPU53987 Plasma—Aldosterone/renin; arbitrary substance ratio(IRP 68/356; procedure) = 20 nanomol per International Unit
Abbreviated form with a result NPU53987 P—Aldosterone/renin; arb.subst.ratio(IRP 68/356; proc.) = 20 nmol/IU
Written expression The arbitrary substance ratio of Aldosterone/renin in Mrs. Smith’s plasma is  [20] nmol/IU. The measurement is performed according to a procedure defined be the laboratory. “IU” and its magnitude is defined by the Certified Reference Material, IRP 68/356 from WHO.


  • Kind-of-property

    • Nominal kind-of-property

    • Kind-of-quantity

      • Unitary kind-of-quantity

        • Rational unitary kind-of-quantity

          • Arbitrary substance ratio


  • 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
2015-06-08 Arbitrary substance ratio Term established