Table 1 Iterated coding hierarchies in the Read 2, CTv3 and SNOMED-CT coding structures categorised as definite, probable and possible when inferring ethnicity
Coding systemDefinite coding hierarchyProbable coding hierarchyPossible coding hierarchy

Read 2
CTv3
SNOMED-CT		Ethnic groups (census)
9S…
XUVqQ
S-0001B		Main spoken language
13l..
XUUSn
F-02B21		Language read
13n..
XUUSm
F-94930

Read 2
CTv3
SNOMED-CT		Ethnic category – 2001 census
9i…
-
-		Additional main spoken language
13u..
-
-		Need for interpreter
9NU..
XaI8W
F-025FB

Read 2
CTv3
SNOMED-CT		Ethnicity and other related national data
9T.
-
F-001A9		Supplemental main language spoken
13w..
UaoHK
F-04502

Read 2
CTv3
SNOMED-CT		Country of Origin
134..
XSCj5
F-03C9A		Language Spoken
13Z6
-
F-028DC

Read 2
CTv3
SNOMED-CT		World languages
13b..
-
-