Page 190 - Registrar Orientation Manual 2016

Reference:
Effective date:
2015
Expiry date:
2018
Page:
16 of 28
Title: Laboratory Testing Guidelines (DRAFT)
Type:
Clinical Guideline
Version:
01
Authorising initials:
Tryptase ($100)
Tryptase testing costs over $40,000 a year. Requests must be endorsed by a SMO.
Tryptase is elevated in some, but not all, anaphylaxis. It is most useful where the diagnosis of anaphylaxis is not clear, for example in collapse immediately following an IV injection or sting without development of mucocutaneous features of histamine release or bronchospasm. It is particularly useful in anaesthesia when several things may account for the collapse.
Tryptase often does not increase in food allergy so if the diagnosis is clear there is no added benefit of doing the test. In patients presenting with recurrent anaphylactic like-symptoms the tryptase may be useful to confirm that anaphylaxis is occurring. The tryptase half-life is 2 hours, so there is no point doing the test the next day. If the tryptase is raised then a repeat level should be taken to ensure it returns to normal. If it remains elevated, then a mast cell disorder is likely.
Microbiology
The estimated annual costs of microbiological testing in Waikato are shown below:
Correct collection of samples is critical. See http://lab.waikatodhb.health.nz/collection-guides/ Blood Culture ($33)
Blood cultures are the second most costly blood test performed at Waikato costing $760,000/yr.
Choosing Wisely has the following:
Do not do blood cultures in patients who are not systemically septic or who have a clear source of infection and in whom a direct specimen for culture (urine, aspirate or sputum) is possible.
Do not order blood cultures for patients with a skin infection (cellulitis, abscess) without sepsis. Do not order blood cultures for patients with a urinary source of infection without sepsis.