Nominal indication obtained from an object similar to the one under investigation, except that the nominal property of interest is supposed not to be present, or is not contributing to the nominal indication.
Example: Nominal indication obtained by examining a serum containing immunoglobulins, but no HLA-antibodies, when the component searched for is HLA-antibodies.
Notes: - A blank nominal indication shall not be confused with a quantity value below a detection limit.
- A blank nominal indication is necessary for quality assessment in some examination procedures.
- A blank nominal indication, when the examination procedure is expected to produce a nominal property value, is an erroneous nominal property value.
- The concept is often termed "negative control", but not here.
Source:
PAC, 2018, 90, 913. 'Vocabulary on nominal property, examination, and related concepts for clinical laboratory sciences (IFCC-IUPAC Recommendations 2017)' on page 920 (https://doi.org/10.1515/pac-2011-0613)