The following service is exposed by the Terminology Service for communicating with the Interoperability Layer:
http://server/validate.php?namespaceCode=CODE&conceptCode=CODE
An example might be:
http://ts.jembi.org/validate.php?namespaceCode=ICD10RW&conceptCode=A00.0
The resulting xml will look as follows on success:
<tsvalidate> <result>1</result> </tsvalidate>
and will return a 0 if the code is invalid.
There's also
<tsvalidate> <result>Invalid Request</result> </tsvalidate>
and
<tsvalidate> <result>Exception</result> <details> … </details> </tsvalidate>
if something goes wrong.