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Test Mnemonic:


Specimen Requirements:

7 mL of blood in Red-topped vacutainer tube. Do not use SST/gel separator vacutainer tube. The optimum time for collection of blood specimen is between 10 and 14 hours after the last dose of medication for patients taking antidepressants once a day and just before the morning dose for patients who are on a divided dose schedule. Lab slip request must include date and time of specimen collection.  

Minimum Volume:

3mL of blood


Delivered to Sample Management within 2 hours of collection.

Specimen Preparation:

Allow specimen to clot completely at room temperature. Centrifuge to separate serum from cells within 2 hours of collection. Transfer serum from collection tube to labeled plastic transport tube. 


Store frozen (if analysis is not performed immediately) for ≤1 year. (Avoid repeated freeze/thaw cycles).   

Causes for Rejection:

Blood drawn in SST/gel separator vacutainer tube, incomplete and/or incorrect sample identification, improper storage/transport, gross hemolysis, icterus or lipemia.   

Reference Range:

By report (reports may vary based on instrumentation, patient age and sex).

Turnaround Time:

  Routine: 3-5 days  




Special Chemistry:  Monday – Friday:  7 am – 3:30 pm.

CPT 4 Code:



Cyclobenzaprine (Flexeril) interferes with the quantitation of amitriptyline; therefore, amitriptyline cannot be quantitated if the patient is also on cyclobenzaprine. Some of the phenothiazines may also interfere.

When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
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