Foundation and linearizations: when residual categories exist

Why some categories have no “other”

Why do some categories have no other category? Because residual categories exist only where they are meaningful.

Y, Z, and F, G

The terminal letter Y is reserved for other specified, and Z for unspecified. In chapters with more than two hundred and forty blocks, F and G are also used, because of limits in the coding space.

• Y · Other · The terminal letter Y is reserved for the residual category other specified.
• Z · Unspecified · The terminal letter Z is reserved for the residual category unspecified.
• F and G · Large chapters · Chapters with more than 240 blocks also use F and G, because of limits in coding space.

From .8 and .9

In ICD-10, residual categories used the numeric characters point eight and point nine. ICD-11 uses the terminal letters Y and Z.

No “other” where it would mislead

Residual categories exist only where they are meaningful. Where a condition is either congenital or acquired, there is no other, but there is an unspecified. And chronic postprocedural conditions have no residual categories at all, deliberately, so users don't classify there conditions that belong elsewhere.

• Rule · Meaningful · Residual categories exist only where they are meaningful.
• Congenital or acquired · No other · Where a condition is only one or the other there is no other, but an unspecified exists.
• Postprocedural · None · Chronic postprocedural conditions have no residual categories, deliberately.

Unspecified or other

When you must choose: unspecified when the information is not in the source documentation. Other when the documentation is very specific but the list has no category, so you code to the closest match.

Check yourself

Pause and think. How did ICD-10 mark its residual categories? The answer: With the numeric characters point eight and point nine. In ICD-10, residual categories used .8 and .9. ICD-11 uses the terminal letters Y and Z.

• With terminal letters Y and Z
• With the letters F and G
• With the numeric characters point eight and point nine
• With the letter X

Keep these in mind

Y is other specified, Z is unspecified. Not every category has an other. And choose by what the documentation says.

• Y other specified, Z unspecified
• Not every category has an “other”
• Choose by what the documentation says