Page 184 - Registrar Orientation Manual 2016

Reference:
Effective date:
2015
Expiry date:
2018
Page:
10 of 28
Title: Laboratory Testing Guidelines (DRAFT)
Type:
Clinical Guideline
Version:
01
Authorising initials:
Prolactin ($14)
The Choosing Wisely recommendations include the following:
Do not perform prolactin levels in infertility investigation if normal menses.
PTH ($28)
PTH testing costs over $120,000 a year. Many tests are repeated. We recommend:
Do not repeat the PTH more frequently than 3 monthly in patients with CKD.
The PTH-related peptide ($136) is an expensive send-away test; the result usually takes weeks to come back and rarely changes the management of patients with malignant hypercalcaemia.
Thyroid Function Tests (‘TFTs’) (TSH is $7, Thyroxine $7)
The Choosing Wisely recommendations include the following:
Don’t order multiple tests in the initial evaluation of a patient with suspected non-neoplastic thyroid disease. Order thyroid-stimulating hormone (TSH), and if abnormal, follow up with additional evaluation or treatment depending on the findings.
Don’t order T3 levels when assessing levothyroxine (T4) dose in hypothyroid patients.
The DHB Shared Services Laboratory Test Referral Guidelines note: Free T3 measurement is useful only in specific clinical settings:
 Evaluation of possible or established hyperthyroidism. It can identify the severity and also patients with low TSH but normal FT4 (either ‘T3 toxicosis’ or early recurrence)
 Monitoring of patients on thyroid replacement in two specific circumstances:
o patients with hypopituitarism, sometimes as an adjunct to measurement of free T4,
because the TSH is typically unreliable in such patients.
o sometimes in monitoring of patients on suppressive treatment for thyroid cancer
 Rare clinical settings of TSH secreting pituitary tumours or defects in thyroid hormone metabolism or action (e.g. congenital deiodinase deficiency, hormone resistance)
We also recommend:
Do not do TFTs as a screening test in hospital admissions.
Do not do TFTs unless there is a clinical indication (for example new AF).
Do not repeat TFTs without a good reason.
Do not repeat TFTs within 4 weeks of starting or changing treatment of thyroid disease except in patients with severe thyrotoxicosis (who should be under Endocrinology).
Our laboratory adds the FT4 if the TSH is elevated and both FT4 and FT3 if the TSH is low.
TSH receptor antibody tests ($72)
TSH receptor antibody tests cost the DHB over $160,000 a year. Ten times as many tests are
currently done as than the annual incidence of new cases of thyrotoxicosis. We recommend:
Do not do TSH receptor antibody tests except in newly diagnosed thyrotoxicosis unless recommended by an Endocrinology SMO.
TSH receptor antibody tests are useful in the work-up of patients with newly diagnosed thyrotoxicosis to identify patients with Grave’s disease. They are used in monitoring selected patients on treatment, patients with thyroid eye disease and in patients with previous treated Grave’s disease who get pregnant. The laboratory will not test specimens more often than 4 weekly. Repeat testing needs support of an Endocrine SMO.