# Case Significance

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 (names of people, organizations, taxonomic groups (e.g. species, genus, family)).

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.

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For more information, see [Organism Naming Conventions](https://snomed-international.gitbook.io/uat-snomed-international-docs/kdfQQ4zexrP8YsnhBh12/specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/organism/organism-naming-conventions).
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#### **Case Sensitivity**

<table><thead><tr><th width="100">Case Sensitivity Indicator</th><th>Values</th><th>Meaning</th><th>Examples</th></tr></thead><tbody><tr><td>cI</td><td>900000000000020002 | Only initial character case insensitive (core metadata concept)|</td><td>First character of the description may or may not be capitalized while the case of the rest of the description cannot be changed</td><td><ul><li>Family history of Prader-Willi syndrome (situation)</li><li>Born in Australia (finding)</li><li>Neonatal jaundice with Dubin-Johnson syndrome (disorder)</li><li>Penicillin resistant Streptococcus pneumoniae (organism)</li></ul></td></tr><tr><td>CS</td><td>900000000000017005 | Entire term case sensitive (core metadata concept)|</td><td><p>Cannot change any case in the description</p><p>Changing case may change the meaning of the term or is not commonly used</p></td><td><ul><li>Down syndrome</li><li>English as a second language (finding)</li><li>pH measurement (procedure)</li><li>mm (qualifier value)</li></ul></td></tr><tr><td>ci</td><td>900000000000448009 | Entire term case insensitive (core metadata concept)|</td><td><p>Entire description may be lower or upper case</p><p>Changing case does not change the meaning of the term</p></td><td><ul><li>Fracture of tibia (disorder)</li><li>Blood compatibility test (procedure)</li><li>Bite of fish (event)</li><li>Floor mat (physical object)</li><li>Gravida</li></ul></td></tr></tbody></table>

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.

<figure><img src="https://4060284305-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FuoSxuN6wQMDYcvuq2wNX%2Fuploads%2FrTTws1zBLsfGkwmPg0xy%2Fimage.png?alt=media&#x26;token=444c05a2-501a-4530-b5c4-290c8eff74c4" alt=""><figcaption><p>Stated view of 365638007 |Finding of Rh blood group (finding)| and subtypes</p></figcaption></figure>

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Case sensitivity can be changed on an existing description without inactivating the description.
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The common name for |Structure of pharyngotympanic tube (body structure)| is eustachian tube. While the term originated eponymously, it is not the name of the person from whom the body structure was named after. Therefore, the case significance is *ci* for case insensitive.
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#### Extensions <a href="#extensions" id="extensions"></a>

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 <a href="#numeric-values" id="numeric-values"></a>

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 *Entire term case insensitive*.

* For example,
  * The concept

    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*.

* For example,
  * The concept

    387407006 | Tioguanine (substance)| has the synonym, 6-TG. Apply the case sensitivity indicator of cl for *Only initial character case insensitive*.

### Special characters <a href="#special-characters" id="special-characters"></a>

Special characters such as <, %, >, . , &, ^, will not display differently if switched between upper and lower case, so numeric values should be treated as case *insensitive* characters in a term. The rules for numeric values apply similarly to special characters.

If a description begins with a special character and the word(s) and/or symbol(s) following the special character begins with a capital letter, the case sensitivity indicator is *cl* for *Initial character case insensitive*.

* For example,
  * The concept

    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* i*nitial character case insensitive*.

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**Greek alphabet characters**\
Words derived from the Greek alphabet, for example, alpha, beta, delta, gamma, omega, etc., are case insensitive wherever they are in the description in the substance hierarchy.
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### Assessment scales and Staging systems <a href="#assessment-scales-and-staging-systems" id="assessment-scales-and-staging-systems"></a>

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.

* For example,
  * Ages and Stages Questionnaires Third Edition (assessment scale)
  * Fagerstrom test for nicotine dependence (assessment scale)
  * National Cancer Institute histologic grading system (staging scale)
  * Clark system for melanoma staging (staging scale)

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**Gram staining**\
Gram staining is a common laboratory technique used to differentiate bacteria based on their cell wall constituents. Laboratory test results may be *Gram positive* or *Gram negative*. The technique was developed by a Danish physician, Hans Christian Gram. Consequently *Gram*, when referring to the technique, should always begin with an upper case *G*.
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