Expressions are produced as part of a fully validated approach including the appropriate knowledge and resources. As part of this approach occasionally expressions will
fail validation, following which a review involving the check list below may be helpful. The commonest problem is a simple "syntax" error, or it may be that invalid (new or inactive) SNOMED terms
are used in the expression which are not in the validation server version which currently lags behind by over a year.
The final step in the process should be a review and clinical sign off, considering that it is quite possible to construct and validate an expression which does not make sense.
