Labeling aspects of general/family practice, such as reasons for encounter and health problems, requires that the available labels reflect the characteristics of the domain: general practice/family medicine. Labels should be derived from a nomenclature or thesaurus. A nomenclature contains all the terms and professional jargon of medicine, and a thesaurus is a storehouse of terms like an encyclopedia or computer tape with a large index and synonyms.

Classification systems provide a structure to order named objects in classes according to established criteria. They do not necessarily contain all terms, and difficulties arise when they are used as a nomenclature and terms are not found within them. Often many terms are included within one rubric, so that the use of coding based on a classification does not provide adequate specificity.

ICPC is a classification which reflects the characteristic distribution and content of aspects of primary care. It is not a nomenclature. The richness of medicine at the level of the individual patient needs a nomenclature and thesaurus much more extensive than ICPC, particularly for recording the specific detail required in an individual patient record. The use of ICPC together with ICD-10 and other classification systems, such as the Anatomical-Therapeutic-Chemical classification of medications (ATC), can provide the basis of an adequate nomenclature and thesaurus, but if full coding is required these must be supplemented by even more specific coding systems. However unless such coding systems are based upon a suitable classification, such as ICPC is for general/family practice, it is not possible to extract coherent data about populations rather than just individuals.