Postcoordination in depth: mandatory, allowed and required links

Not every link is optional

Not every postcoordination link is optional. ICD-11 marks some as mandatory, and some as allowed.

When detail must be added

Some categories are incomplete on their own for the several purposes of the ICD. For those, postcoordination is mandatory, and the coding tool marks the axis. Allowed postcoordination is optional detail you may add. The causing condition is the clearest mandatory case: it must be coded when it is known.

• Mandatory · Incomplete · Applies where a category is incomplete for the multiple purposes of the ICD. The coding tool marks these axes.
• Allowed · Optional · Available detail you may add. The coding tool marks these with a different icon.
• Causing condition · When known · Added to categories caused by an underlying disease: it must be coded when known.

Optional, and together

Has manifestation is optional, and allowed in almost all situations. Associated with is used when several codes are needed to describe a condition fully. For example, it links the codes for antimicrobial resistance to the codes for the infection. It can be allowed or required, depending on the situation.

• Has manifestation · Optional · Allowed in almost all situations. The listed manifestations are usually a sample.
• Associated with · Together · Used when several codes are needed to describe a condition fully, without implying cause.

Infection, and its resistance

WHO's example. A urinary tract infection due to Escherichia coli, associated with extended spectrum beta-lactamase producing Escherichia coli. Two stem codes, joined with a slash.

• Condition · GC08.0 · Urinary tract infection due to Escherichia coli.
• Associated with · MG50.27 · ESBL-producing Escherichia coli.

Three rules for causes

WHO lists special cases. External cause codes are allowed to identify the cause of an injury. The external cause for a specific drug is allowed with drug-induced entities. And the mode and mechanism of health care related harm are associated with the harm codes.

• Injuries · Allowed · External cause codes are allowed to identify the cause of an injury, and are associated with it.
• Drug-induced · Allowed · The external cause code for a specific drug is allowed with entities such as “drug-induced”.
• Health care harm · Associated · External cause codes for the mode and mechanism of harm are associated with the harm codes.

Check yourself

Pause and think. How does WHO describe the 'has manifestation' axis? The answer: Optional, and allowed in almost all situations. Has manifestation is optional and allowed in almost all situations.

• Mandatory whenever a manifestation is documented
• Optional, and allowed in almost all situations
• Never allowed with a stem code
• Required only for injuries

Keep these in mind

The causing condition is mandatory when known. Manifestation is optional. Associated with is allowed or required, and implies no cause. And the coding tool marks the mandatory axes.

• Causing condition: mandatory when known
• Manifestation: optional
• Associated with: allowed or required, no cause implied
• The coding tool marks mandatory axes