As of November 25, 2019, LifeLabs began working on implementing some changes to its thyroid testing processes in British Columbia (BC) to align with new guidelines published by the Guidelines and Protocol Advisory Committee.
The guideline includes specific recommendations regarding thyroid function testing and monitoring of thyroid function disorder. In particular, the new guideline includes a laboratory algorithm that includes changes in the reflex testing of TSH to FT4/FT3.
In addition, the guideline expands the scope to include pediatric and pregnant patients, and there will be trimester-specific gestational reference intervals for TSH and FT4 appended to all women aged 15 to 50 years of age. There are no changes in FT3 reference intervals in pregnancy.
The laboratory algorithm for reflex testing will be followed for most patients, but the guideline includes specific clinical indications when the new reflex rules do not apply. These comprise of the following:
- The patient is less than a year old at the time of sample collection.
- The patient is suspected to have pituitary/hypothalamic insufficiency and is specifically diagnosed with pituitary, hypothalamic, hypothalamus, secondary hypothyroidism, or tertiary hypothyroidism.
- The patient’s previously reported TSH level is inconsistent with the patient’s presentation. This requires consultation with a laboratory physician, pathologist, or clinical biochemist before giving the patient a new requisition for testing.
- An error or interference in the results is suspected and a follow-up test is required. This must be written on the requisition.
The changes to reflex testing include:
- If TSH is ≥10 mU/L and FT4 is within the reference interval, then FT3 will be reflexed. If the TSH is <10 mU/L, FT3 will not be reflexed.
- If FT4 and FT3 are ordered without a TSH, these tests will not be performed unless a Special Clinical Indication is noted on the laboratory requisition (see above).
All reference intervals are specific to the Abbott Architect methods used at LifeLabs.
For further information please see the BC Guidelines at bcguidelines.ca