Background: Subclinical hypothyroidism is an entity based on the
laboratory findings of a raised serum thyrotrophin (TSH) concentration and a normal
free thyroxine (FT4) concentration. Patients with subclinical
hypothyroidism who also have anti-thyroid peroxidase (TPO) antibodies have a higher
conversion to overt hypothyroidism than those without, and treatment with thyroxine
is recommended.
Method: We audited anti-TPO assay requests within two NHS Trust
hospitals, against consensus standards, to ascertain whether a cascade approach to
anti-TPO testing and direct advice leads to more appropriate prescribing of thyroxine
in general practice.
Results: Our data show that where anti-TPO status was automatically
tested for and clear advice for treatment given, >85% of patients were treated
according to the standard required by the consensus document, with >90% of those
recommended to be commenced on thyroxine actually doing so. In contrast, where
anti-TPO was not routinely assessed, treatment was started in 46% of patients,
without clear evidence that this was appropriate.
Conclusion: In order to better advise clinicians and in accordance with
the agreed protocol, laboratory-generated cascade testing for anti-TPO antibodies
should be an integral part of the investigation of subclinical hypothyroidism, and
reports should contain appropriate interpretation and advice.
