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Generally, SNOMED CT descriptions begin with an upper case letter; the rest of the words in the description are lower case, except for abbreviations , and proper nouns, i.e. names (names of people, organizations, taxonomic groups (e.g. species, genus, family), etc). 

With regard to organism naming:

• Non-taxonomic groupers, such as “Human herpes simplex virus”, are recorded with a case sensitivity indicator of Entire term case insensitive (ci).
• There are cases where the authoritative resources do not have an entry for the official name of an organism. For these concepts, the associated literature is referenced for naming and case sensitivity assignments.
  • For example,
    • “Severe acute respiratory syndrome coronavirus 2” is below species level and does not have an entry in the authoritative resource, International Committee on Taxonomy of Viruses (ICTV).  Therefore, it is recorded with a case sensitivity indicator of Entire term case insensitive (ci), since the majority of references do not capitalize “severe”.
• When an organism is part of the term of a concept in another hierarchy, it is capitalized.  However, when the general reference to the organism is part of the term, the term in the description is not capitalized.
  • For example, 

• • • 19431000 |Infective arthritis caused by Rubella virus (disorder)| - Since the Rubella virus is specified, Rubella is capitalized. 
    • 1857005 |Congenital rubella syndrome (disorder)| - Since rubella refers to the disease, rubella is not capitalized. 

• • • 293120003 |Adverse reaction to component of vaccine product containing Vaccinia virus antigen (disorder)| - Since the species Vaccinia virus (of the genus Orthopoxvirus) is specified, Vaccinia is capitalized. 
    • 56978007 |Generalized vaccinia (disorder)| - Since vaccinia is describing a condition, vaccinia is not capitalized.

Special attention is to be paid to the possibility of altering the semantics of those concepts whose FSN uniqueness depends upon case significance. 

For example, 

• The subtypes of 365638007 |Finding of Rh blood group (finding)| vary in meaning depending upon the description's case of the letters c, d, and e.

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Figure 1.  Stated view of 365638007 |Finding of Rh blood group (finding)|

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subtypes

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Extensions

SNOMED CT includes three case significance values, "ci", "cI" and "CS". However, this range of values depends on the languages and linguistic norms. For the International Edition, where the first character of descriptions is always capitalized, the value "Only initial character case insensitive" ("cI") is necessary. This value is not required for descriptions in extensions that do not adhere to this convention. When appropriate, it is also acceptable to limit the range to a single case significance value.

Numeric values

Numeric values will not display differently if switched between upper and lower case, so numeric values should be treated as case insensitive characters in a term.  

If a description begins with a numeric value and the word following the number does not begin with a capital letter, the case sensitivity indicator is ci for E ntire Entire term case insensitive.

For example,

• • The concept 

    Concept
    t 33635003 |Serotonin (substance)|

     has the synonym, 5-hydroxytryptamine.  The description is recorded in SNOMED CT in lower case, not 5-Hydroxytryptamine, but the case sensitivity indicator is ci  for Entire term case insensitive.

If a description begins with a numeric value and follows with an abbreviation that contains a capital letter, the case sensitivity indicator is cl for Initial character case insensitive.

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• • The concept 

    Concept
    t 277976001 |Less than 35 degrees C (qualifier value)|

     has the synonym, <35 degrees C.  The description starts with a special character that is case insensitive but contains an abbreviation "C" for Celsius that is case sensitive, so the case sensitivity indicator applied to the synonym is cl for Only initial character case insensitive.

Assessment scales and

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Staging systems

SNOMED CT descriptions representing assessment scales and staging systems should be capitalized per the name of the scale or staging system. Legacy concepts may not follow this pattern.

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