Arbitrary substance concentration increment (arb.subst.c.incr.) - Dynamic NPU Manual

Arbitrary substance concentration increment (arb.subst.c.incr.)



Definition in words

Arbitrary substance concentration of component B in conditioned system 1 minus arbitrary substance concentration of component B in conditioned system 0

Definition by equation

Note: kprocedure is a constant defined by the measurement procedure (there is an approximately proportionality to a kind-of-quantity from the International System of Quantities).

Result type

Differential scale
  • Value sets are numerical values on a differential scale
  • Numerical values -∞ to ∞
  • Values cannot be divided
  • Possible comparison (a-b = c-d; a-b ≠ c-d)


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 ratio scale is attributed to the NPU definition, the unit is a non-SI unit. 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 an international certified reference material, the laboratory can specify the unit at the placeholder, procedure defined unit.

If ordinal scale is attributed, no unit is stated.


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 NPU08765 P—Thyrotropin; arb.subst.c.incr.(IRP 80/558; max. c. minus 0 min c.; proc.) = ? × 10-3 IU/L
Full form with a result NPU08765 Plasma—Thyrotropin; arbitrary substance concentration increment(IRP 80/558; maximum concentration minus 0 minimum concentration; procedure) = 4 × 10-3 IU/L
Abbreviated form with a result NPU08765 P—Thyrotropin; arb.subst.c.incr.(IRP 80/558; max. c. minus 0 min c.; proc.) = 4 × 10-3 IU/L
Written expression The arbitrary substance concentration increment of Thyrotropin in Mr. Smith’s plasma is [4] × 10-3 IU/L. The measurement is performed according to a procedure defined by the laboratory, where the result is maximum concentration minus 0 minimum concentration. “IU” and its magnitude is defined by the Certified Reference Material, IRP 80/558 from WHO.
  • Kind-of-property

    • Nominal kind-of-property

    • Kind-of-quantity

      • Unitary kind-of-quantity

        • Differential unitary kind-of-quantity

          • Arbitrary substance concentration increment


  • 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 substance concentration increment Term established