Test ID: THSCM
Thyroid Function Cascade, Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Screening for a diagnosis of thyroid disease
Thyroid function assessment using a cost- and time-efficient testing algorithm
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| STSHC | TSH, Sensitive, S | Yes, (order STSH) | Yes |
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| FRT4C | T4 (Thyroxine), Free, S | Yes, (order FRT4) | No |
| TPOC | Thyroperoxidase Ab, S | Yes, (order TPO) | No |
| T3C | T3 (Triiodothyronine), Total, S | Yes, (order T3) | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If thyroid-stimulating hormone (TSH) is <0.3 mIU/L, then free T4 (FT4) is performed at an additional charge.
If FT4 is normal and the TSH is <0.1 mIU/L, then T3 is performed at an additional charge.
If TSH is >5.0 mIU/L, then FT4 and thyroperoxidase antibodies are performed at an additional charge.
See Thyroid Function Ordering Algorithm in Special Instructions.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
STSHC/6353: Electrochemiluminescent Immunoassay
FRT4C/33096, TPOC/33095: Chemiluminometric Immunoassay
T3C/33094: Immunoenzymatic Assay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 1.5 mL
Forms: If not ordering electronically, submit a General Request Form (Supply T239) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Frozen | 30 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The Thyroid Function Cascade, Serum utilizes a cascaded testing procedure to efficiently evaluate and monitor functional thyroid status. When ordered, physicians automatically obtain a series of tests that will rapidly provide comprehensive thyroid results for their patients. This test will significantly reduce the cost of care for patients by eliminating downstream costs associated with expensive redraws, repeat orders, return office visits, extended hospital stays, and physician time.
The cascade begins with sensitive-thyroid–stimulating hormone (s-TSH), a highly effective screening assay. In patients with an intact pituitary-thyroid axis, s-TSH provides a physiologic indicator of the functional level of thyroid hormone activity. Increased s-TSH indicates inadequate thyroid hormone, and suppressed s-TSH indicates excess thyroid hormone.
Transient s-TSH abnormalities may be found in seriously ill, hospitalized patients, so this is not the ideal setting to assess thyroid function. However, even in these patients, s-TSH works better than total thyroxine (an alternative screening test).
The majority of these screens will be normal and no further testing will be necessary. However, when the s-TSH result is abnormal, appropriate follow-up tests will automatically be performed.
If s-TSH is <0.3 mIU/L or >5.0 mIU/L, free thyroxine (FT4) is performed. The supplemental measurement of FT4 in patients with abnormal s-TSH measurements allows one to better asses the severity of the changes.
Serum triiodothyronine (T3) levels often are depressed in sick and hospitalized patients, caused in part by the biochemical shift to the production of reverse T3. Therefore, T3 generally is not a reliable predictor of hypothyroidism. However, in a small subset of hyperthyroid patients, hyperthyroidism may be caused by overproduction of T3 (T3 toxicosis). To help diagnose and monitor this subgroup, T3 is measured on all specimens with suppressed s-TSH and normal FT4 concentrations.
Detectable concentrations of antithyroperoxidase (anti-TPO) antibodies are observed in patients with autoimmune thyroiditis and may cause the destruction of thyroid tissue, resulting in the eventual hypothyroidism. Anti-TPO antibodies are measured in all specimens with elevated s-TSH concentrations.
See Thyroid Function Ordering Algorithm in Special Instructions.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
> or =12 months: 0.3-5.0 mIU/L
Reference values have not been established for patients that are <12 months of age.
Interpretation Provides information to assist in interpretation of the test results
See individual unit codes for additional information.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Two important patient groups may require alternate thyroid function testing strategies: patients with pituitary disease and patients with neuropsychiatric disorders. These patients may require endocrinologic consultations, because the sensitive-thyroid stimulating hormone measurement may be misleading and additional tests probably are necessary.
Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedure, may have circulating antianimal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Feldt-Rasmussen U: Analytical and clinical performance goals for testing autoantibodies to thyroperoxidase, thyroglobulin and thyrotropin receptor. Clin Chem 1996;42:160-163
2. Fatourechi V, Lankarani M, Schryver PG, et al: Factors influencing clinical decisions to initiate thyroxine therapy for patients with mildly increased serum thyrotropin (5.1-10.0 mIU/L). Mayo Clin Proc 2003;78:554-560
3. Wilson J, Foster D, Kronenburg H, et al: Williams Textbook of Endocrinology. Ninth edition, WB Saunders Company, 1998
Method Description Describes how the test is performed and provides a method-specific reference
See individual unit codes for additional information.
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Sunday; Continuously
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
84443-Thyroid-stimulating hormone-sensitive (s-TSH)
84439-T4 (thyroxine), free (if appropriate)
84480-T3 (triiodothyronine), total (if appropriate)
86376-Thyroperoxidase (TPO) antibodies (if appropriate)
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| STSHC | TSH, Sensitive, S | 11579-0 |
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