Exclusion guidelines from WHO coding publications will be evaluated as a last step in mapping context evaluation.

Review of alpha modifiers:

There are two types of modifiers which appear in the ICD-10 Alphabetical Index, Volume 3. These are non-essential and essential modifiers.
Non-essential modifiers appear in parentheses following the terms they modify and do not affect the target code selection for a given condition, sign or symptom but are considered as alternatives to the expression of the term.

Essential modifiers appear next to a lead term or as subterms indented below lead terms in the alphabetical index and do affect the selection of target code. They describe essential differences in site, etiology or type of disorder and must appear in the clinical statement for the code to be assigned. When an essential modifier denotes an alternative map target to the source term statement, the modifier will be considered as a possible exclusion to the initial map target selected.

The Mapping Specialist will review the WHO ICD-10 Alphabetical Index to Diseases and Nature of Injury in Volume 3 to identify any essential modifiers which represent SNOMED CT concepts that are descendants of: a) the source concept to be mapped, or b) the source concept etiology SNOMED CT code when dagger and asterisk guidance requires a separate target for cause of the disorder. The Mapping Specialist will add new Map members with the associated target specific to the alpha reference as context dependent maps with a mapRule.
For example (Etiology and Manifestation):
420485005 | Herpetic iridocyclitis (disorder) | maps to B00.5, Herpes viral ocular disease and H22.0, Iridocyclitis in infectious and parasitic diseases classified elsewhere. (Exemplar: Dagger & Asterisk: #3)
Iridocyclitis
-herpes, herpetic (simplex) B00.5† H22.0*
OR
Herpes, Herpetic
-iridocyclitis (simplex) B00.5† H22.0*
For example:
414924006 | Obstructed incisional ventral hernia (disorder) | maps to K43.0, Ventral hernia with obstruction, without gangrene. Upon reviewing the WHO alphabetic index, the Mapping Specialist notes Incisional hernia has a reference to "see Hernia, ventral". To determine the target, the Mapping Specialist follows the 'see' reference and checks under "Hernia, ventral". ICD-10 code K43.0 is listed under Hernia, ventral, with, obstruction. In addition, there are essential and nonessential modifiers to consider:
Hernia, hernial (acquired) (recurrent) K46.9
-incisional — see Hernia, ventral
Hernia, hernial (acquired) (recurrent) K46.9
-ventral K43.9
--with
---gangrene (and obstruction) K43.1
---obstruction K43.0
Mapping for concepts of poisoning and overdose will require analysis of the Alphabetic Index; Table of Drugs and Chemicals. This table organizes the default target codes for mapping drug or chemical mishaps including advice for accidental events, intentional self-harm, undetermined intent and adverse effects in therapeutic use. This table also may include essential modifiers which require attention for possible exclusion rules. For example, when mapping the SNOMED CT source concept 295830007 | Overdose of antidepressant drug (disorder) | a review of the drugs table will expose these entries for antidepressant poisoning:

In this case, the default target code for mapping of Antidepressant poisoning is T43.2 for mapGroup one and X41 for mapGroup two based upon WHO advice of assumption of accidental intent when unspecified. Note that required modifiers are identified for this map for agents MAO inhibitors, triazolpyridine, tricyclic and tetracyclic antidepressants.


Atomic mapping (obsolete)
When the Mapping Specialist encounters a source concept with ten or fewer descendants, only the main concept will be examined for mapping.