The most conclusive evidence for using thyroid peroxidase antibody (TPO) is predictive in nature when evaluating possible subclinical hypothyroidism. If this test is positive, hypothyroidism occurs at a rate of 4.3% per year versus 2.6% per year when the antibody is negative. While this scenario does not cover all clinical indications for ordering TPO, there is no definitive evidence that repeat TPO testing provides additional information.1
Based on this information the ordering of TPO within Spectrum Health is being modified. If the test is ordered more than once on a patient, a screen will appear in EPIC indicating the following: “This test should typically only be resulted once per lifetime. The duplicate checking indicates that this patient has already had this testing performed. Please see chart review for results.” This is not a “hard stop” but providers will need to click “Continue” to proceed with the order.
Effective immediately, Anti-Thyroglobulin (Anti-TgAb) requests if received in conjunction with Thyroglobulin Tumor Marker (Tg-TM) requests, will be canceled. Tg-TM tests are sent to Mayo Medical Laboratory; where both Tg-TM and Anti-TgAb are performed and resulted as part of the Tg-TM order. This is a laboratory best practice as anti-thyroglobulin autoantibodies (Anti-TgAb), which occur in 15% to 30% of thyroid cancer patients, could lead to misleading Tg results (falsely positive or falsely negative).
Questions may be directed to Dr. David Alter, using the “Contact Us” link above.
As of February 7, 2017 the method/instrument used for the Growth Hormone assay performed at the Spectrum Health Regional Laboratory will be switched from ROCHE COBAS to the IDS- iSYS. A method comparison between the two methods showed excellent clinical and numerical comparability. The assay also performed excellently in terms of precision and linearity.
Thyroid Peroxidase Antibody (anti-TPO), Blood Level (Test #8524 )
This is the recommended test for the evaluation of Autoimmune Thyroiditis
Thyroglobulin, Tumor Marker, Serum (Test #3069)
It is only indicated for monitoring of thyroid cancer treatment.
This result is reported with an Anti-Tg result to assess for possible interference.
This test should NOT be ordered for associated anti-Tg result provided by reference laboratory.
Thyroglobulin Antibody (anti-Tg) Test
Historically ordered with anti-TPO for evaluation of possible autoimmune thyroiditis.
The literature shows that anti-TPO, alone, has better sensitivity and specificity with only 5% of cases of Autoimmune thyroiditis with anti-TPO negative, anti-Tg positive.
Since 2/2011, requests for anti-Tg have been cancelled per Laboratory Communication: Memo Thyroglobulin Antibody 2/2011
Spectrum Health Regional Laboratory Experience February 2015 – March 2016 (13 months):
357 patients with both Anti-TPO and Anti-Tg results.
*Anti-Tg results were due to concomitantly ordered Thyroglobulin TM requests.
250 patients had positive Anti-TPO and/or Anti-Tg level
193 patients had both positive Anti-TPO and Anti-Tg level
56 patients had positive Anti-TPO and negative Anti-Tg level
1 patient had a negative Anti-TPO and positive Anti-Tg levels
Based on these results, and what is reported in the literature, we are confident of our current practices and strongly request discontinuation of Thyroglobulin TM requests for the associated Anti-Tg result
Caturegli P, De Remigis A, Rose NR. Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmun Rev. 2014 Apr-May;13(4-5):391-7
We are currently evaluating serum Thyroglobulin Tumor Marker test ordering practices as the volume has quadrupled over the last 3 years without a quadrupling of total laboratory volume.
If you order this test, please contact Dr. David Alter with the reason for ordering the test.
Of note, the only stated reason in “UPTODATE” is monitoring for recurrence of medullary thyroid cancer status post treatment.
- Monitoring treatment
- Serum thyroglobulin as a marker for autoimmune thyroiditis
- Serum thyroglobulin ordered for the accompanying anti-thyroglobulin antibody result
- Other, please elaborate.