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Chemistry

Chemistry, Education & Training, Test Utilization

Cardiac Marker Testing (Troponin)

Cardiac marker (Troponin) testing should only be ordered for Inpatient or Emergency Department patients. This test is not clinically appropriate for outpatient testing due to long outpatient test turnaround time (specimen collection to result). In cases of acute/urgent medical conditions, please have the patients evaluated at an Urgent Care center or the Emergency Department. Continue Reading

Chemistry, Referral/Sendouts, Test Utilization

Appropriate Thyroglobulin Tumor Marker and Anti-Thyroperoxidase Ordering Practices

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

Chemistry, Test Utilization

Ammonia, NH3

As of March 1, 2016, Spectrum Health Laboratory, Grand Rapids, will no longer draw or send a courier for outpatient Ammonia testing (#8074). If outpatient Ammonia testing is needed, the patient must be collected at the 35 Michigan Draw Site. If outpatient Ammonia testing is needed and the patient cannot be drawn at the 35 Michigan Draw Site, approval must be obtained from Dr. David Alter or the Clinical Pathologist on-call, prior to ordering the test.

There will be no changes to inpatient collection. Note: Inpatients are patients who have been admitted to a hospital in the Medical Center (HDVCH, Butterworth, and Meijer Heart Center) or Blodgett Hospital.

Any questions concerning these changes may be directed to Dr. David Alter in the Pathology Department.

Advanced Technology Laboratory, Chemistry, Molecular Diagnostics

Hepatitis C Antibody Reporting Change

The Spectrum Health Laboratory is now reporting all Hepatitis C Antibody results as Negative or Positive only. (Hepatitis C Antibody, Screening; Hepatitis C Antibody, Diagnostic) The separate Low Positive result category has been eliminated.

The Laboratory has changed to a new Hepatitis C Antibody reagent which no longer includes the Low Positive result category in its product labeling (the FDA approved instructions which laboratories are required to follow). The Low Positive category was defined on the basis of old guidelines which indicated that results above a defined S/CO (signal/cutoff) value were considered to have a 95% or greater probability of being true positives and did not require RIBA confirmation. The RIBA confirmatory test has not been available for several years now. Current guidelines are that all positive Hepatitis C Antibody tests should be confirmed with a HCV RNA test. The Spectrum Health laboratory reflexes all positive antibody results to this test. A positive HCV RNA following a positive antibody result should be considered indicative of active HCV infection, and may be used as a baseline for antiviral therapy.

Any questions concerning this change in Hepatitis C Antibody reporting may be directed to Dr. Richard Horvitz in the Pathology department.