Severity, laterality and temporality in practice

Same condition, more detail

A stem code names the condition. Extension codes carry the detail it does not: how severe, which side, how it unfolded.

Three kinds of detail

Three kinds of detail come up constantly. Severity, which is a scale value. Laterality, which side. And temporality, the course of the condition, such as acute. Extension codes are never used without a stem code, and they never come first.

• Severity · Scale value · A severity scale value is one of the Type 1 extension axes.
• Laterality · Left or right · Which side. The guide's examples use left and right values.
• Temporality · The course · The course of the condition, such as acute.

Which side: left or right

Laterality tells you which side. Take a right cataract. The stem code is cataract, unspecified. The extension is right. Stem first, then the extension, joined with an ampersand. For left, the extension is a different one, and the structure stays the same.

• 9B10 · Stem code · Cataract, unspecified.
• XK9K · Extension · Right.

The course of the condition

Temporality records the course of the condition. Atrial fibrillation is the stem code. Acute is the temporal pattern and onset extension. Joined with an ampersand, they describe acute atrial fibrillation.

• BC81.3 · Stem code · Atrial fibrillation.
• XT5R · Extension · Acute: the temporal pattern and onset.

Severity is an axis too

Severity works the same way. It's an extension axis you add when the documentation states how severe the condition is. Look up the value in WHO's browser or coding tool, rather than from memory.

• The axis · Scale value · Severity is added when the documentation states it.
• The value · Look it up · Find the value in WHO's browser or coding tool rather than from memory.

Timing: when it arose

Some extensions work differently. Diagnosis timing says whether a condition was present on admission, or developed after admission. A code can carry several: acute atrial fibrillation, developed after admission, postoperative. All joined with ampersands.

• On admission · XY6M · Present on admission.
• After admission · XY69 · Developed after admission.

Check yourself

Pause and think. For statistical coding, an extension code: The answer: Can never be used without a stem code. Extension codes can never be used without a stem code for statistical purposes, and can never appear in the first position of a cluster.

• Can stand alone if it describes severity
• Can be the first code in a cluster
• Can never be used without a stem code
• Replaces the stem code once added

Keep these in mind

Extension codes add detail, and are never alone or first. Left and right are laterality values. Acute is a temporality value. And look severity values up, don't guess them.

• Extension codes add detail; never alone, never first
• Laterality: XK8G left, XK9K right
• Temporality: XT5R acute
• Look severity values up; do not guess them