Skip Ribbon Commands
Skip to main content
Sign In

25438 Thyroid Diagnostic Cascade

Thyroid Diagnostic Cascade
Test Code: THYDC
Synonyms/Keywords
TSH, Thyrotropin, Free-T4, Thyroid reflex
Test Components
3rd Gen TSH, and when indicated Free-T4 (Free Thyroxine)
Useful For
This test grouping is offered to aid providers in obtaining appropriate diagnosis for common thyroid disorders.
Refer to Thyroid Function Ordering Algorithm.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​No ​Serum or Plasma ​Serum Separator Tube (SST), Lithium-heparin Plasma Separator Tube (PST) ​Red Top Tube (RTT), Sodium-heparin Green Top Tube (GTT) ​1.0 mL ​0.8 mL ​0.6 mL
Collection Processing Instructions
Separate serum or plasma from the blood within 60 minutes of venipuncture. Specimen must be free of particulate matter including fibrin. Specimens collected in the RTT must be removed from the cells within one hour for storage or transport. Specimens collected in gel-barrier tubes must be removed from the primary tube prior to transporting to Marshfield. Do not send primary collection tube. Specimen should be transported refrigerated (2 - 8°C). If sent frozen, specimens must be completely thawed, thoroughly mixed, and centrifuged before analysis. 1 freeze/thaw cycle has shown to have no qualitative difference in results.
Specimen Stability Information
Specimen Type Temperature Time
​Serum/Plasma ​ ​ ​Ambient ​8 hours
​Refrigerate ​7 days
​Frozen at -20 deg Celsius ​30 days
Rejection Criteria
​Plasma samples in wrong anticoagulant
Specimen not separated from cells within 60 minutes​
Samples not transported refrigerated​
Gross hemolysis​
Interference
Gross hemolysis. Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedure, may have circulating anti-animal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.
 
High doses of exogenous biotin (also termed Vitamin B7, Vitamin H or Coenzyme R) may interfere with this assay. It is recommended that patients refrain from consuming any multivitamin or supplement containing biotin for at least 72 hours prior to collection of a blood sample.
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Chippewa Falls ​​Monday through Friday ​​Less than 2 hours ​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Diagnostic Treatment Center ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Eau Claire ​​Monday through Sunday ​​Less than 2 hours Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Flambeau Hospital ​Monday through Sunday​ ​​Less than 2 hours Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Ladysmith Medical Center ​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Lakeview Medical Center ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Marshfield ​Monday through Sunday ​Less than 2 hours Competitive Immunoassay using Direct Chemiluminescent Technology/Siemens Centaur
Merrill​ ​​Monday through Saturday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Minocqua ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
Stevens Point​ ​Monday through Friday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
Wausau​ ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Wisconsin Rapids ​Monday through Friday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
Test Information

​​The Thyroid Diagnostic cascade has been designed as a diagnostic tool to aid in the initial diagnosis of common adult thyroid disorders. This panel is not intended for use in pediatric patients or in monitoring patients receiving treatment for thyroid disease. This cascade is also not appropriate to use to diagnose primary thyroid neoplasm. The diagnostic cascade begins with sensitive-thyroid–stimulating hormone (TSH), a highly effective screening assay. In patients with an intact pituitary-thyroid axis, TSH provides a physiologic indicator of the functional level of thyroid hormone activity. Increased TSH indicates inadequate thyroid hormone, and suppressed TSH indicates excess thyroid hormone.

TSH: TSH is most often used for the evaluation of the thyroid axis, proper understanding of its utility and limitations is clinically important.

TSH concentrations follow a diurnal rhythm: it typically peaks around midnight and nadir around mid-day. Reference intervals are generally obtained from subjects tested in the daytime, closer to nadir than peak, therefore, when evaluating patient’s serial TSH concentrations, differences in sample collection time should be considered.

TSH Variability: TSH has moderate intra-individual variability and marked inter-individual variability. Since the intra-individual variation is considerably less, when comparing a specific patient’s current TSH level a better approach is to compare with any past level than comparing the patient’s current TSH level to the reference interval. A difference of 0.7 mIU/L or greater is considered significant when evaluating a patient’s serial TSH values.

Method Dependency: TSH methods do not always yield the same result. As much as a 10% difference between results may be generated from different TSH methods. Therefore, the same method should be used when monitoring TSH concentration over time. Similarly TSH reference intervals are also method-dependent and are appropriately applied only to patient results generated from the same method.

Free-T4: Free thyroxine comprises a small fraction of total thyroxine. The free T4 (FT4) is available to the tissues and is, therefore, the metabolically active fraction. Free thyroxine (FT4) are most commonly used in preference to total hormone measurements (TT4 or TT3) to improve the diagnostic accuracy for detecting hypo- and hyperthyroidism in patient populations with the thyroid hormone binding abnormalities.

Reference Range Information
Performing Location Reference Range
All Sites using Dimension Analyzer​
TSH: All Ages 0.35-4.50 uIU/mL
​Free T4: >=18 years 0.7-1.4 ng/dL
​Marshfield
​TSH:
<1 years: 0.70-8.21 uIU/mL
1-11 years: 0.64-6.27 uIU/mL
12-17 years:  0.51-4.94 uIU/mL
>=18 years: 0.55-4.78 uIU/mL
 
Free T4: 
<1 month: No reference range established
1 mo.-12 years:  0.9-1.4 ng/dL
13-20 years:  0.8-1.4 ng/dL
>20 years:  0.9-1.8 ng/dL
Interpretation

The majority of these screens will be normal and no further testing will be necessary. However, when the TSH result is abnormal, free T4 (test code T4-FREE) will automatically be performed. Interpretive comments and further test recommendations will be reported based on the TSH and free T4 results.
Refer to Thyroid Function Ordering Algorithm.

The TSH results should be interpreted in light of the total clinical presentation of the patient, including: symptoms, clinical history, data from additional tests, and other appropriate information. This assay is not validated for testing neonatal serum TSH levels.

Dopamine and glucocorticoids lower TSH secretion.

 Non-thyrometabolic disorders may cause abnormal free T4 levels. Anticonvulsant drug therapy (particularly phenytoin) may result in decreased free T4 levels due to an increased hepatic metabolism. Lithium and iodide preparations lower FT4 levels.

Patients on heparin therapy may have elevated free T4 levels due to release of non-esterified fatty acids, this can alter the relationship between free and bound hormones.

Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
84443​ ​1 ​TSH
​84439 ​1 ​Free T4 ​if needed
Synonyms/Keywords
TSH, Thyrotropin, Free-T4, Thyroid reflex
Test Components
3rd Gen TSH, and when indicated Free-T4 (Free Thyroxine)
Ordering Applications
Ordering Application Description
​COM ​Thyroid Diagnostic Cascade
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​No ​Serum or Plasma ​Serum Separator Tube (SST), Lithium-heparin Plasma Separator Tube (PST) ​Red Top Tube (RTT), Sodium-heparin Green Top Tube (GTT) ​1.0 mL ​0.8 mL ​0.6 mL
Collection Processing
Separate serum or plasma from the blood within 60 minutes of venipuncture. Specimen must be free of particulate matter including fibrin. Specimens collected in the RTT must be removed from the cells within one hour for storage or transport. Specimens collected in gel-barrier tubes must be removed from the primary tube prior to transporting to Marshfield. Do not send primary collection tube. Specimen should be transported refrigerated (2 - 8°C). If sent frozen, specimens must be completely thawed, thoroughly mixed, and centrifuged before analysis. 1 freeze/thaw cycle has shown to have no qualitative difference in results.
Specimen Stability Information
Specimen Type Temperature Time
​Serum/Plasma ​ ​ ​Ambient ​8 hours
​Refrigerate ​7 days
​Frozen at -20 deg Celsius ​30 days
Rejection Criteria
​Plasma samples in wrong anticoagulant
Specimen not separated from cells within 60 minutes​
Samples not transported refrigerated​
Gross hemolysis​
Interference
Gross hemolysis. Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedure, may have circulating anti-animal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.
 
High doses of exogenous biotin (also termed Vitamin B7, Vitamin H or Coenzyme R) may interfere with this assay. It is recommended that patients refrain from consuming any multivitamin or supplement containing biotin for at least 72 hours prior to collection of a blood sample.
Useful For
This test grouping is offered to aid providers in obtaining appropriate diagnosis for common thyroid disorders.
Refer to Thyroid Function Ordering Algorithm.
Test Components
3rd Gen TSH, and when indicated Free-T4 (Free Thyroxine)
Reference Range Information
Performing Location Reference Range
All Sites using Dimension Analyzer​
TSH: All Ages 0.35-4.50 uIU/mL
​Free T4: >=18 years 0.7-1.4 ng/dL
​Marshfield
​TSH:
<1 years: 0.70-8.21 uIU/mL
1-11 years: 0.64-6.27 uIU/mL
12-17 years:  0.51-4.94 uIU/mL
>=18 years: 0.55-4.78 uIU/mL
 
Free T4: 
<1 month: No reference range established
1 mo.-12 years:  0.9-1.4 ng/dL
13-20 years:  0.8-1.4 ng/dL
>20 years:  0.9-1.8 ng/dL
Interpretation

The majority of these screens will be normal and no further testing will be necessary. However, when the TSH result is abnormal, free T4 (test code T4-FREE) will automatically be performed. Interpretive comments and further test recommendations will be reported based on the TSH and free T4 results.
Refer to Thyroid Function Ordering Algorithm.

The TSH results should be interpreted in light of the total clinical presentation of the patient, including: symptoms, clinical history, data from additional tests, and other appropriate information. This assay is not validated for testing neonatal serum TSH levels.

Dopamine and glucocorticoids lower TSH secretion.

 Non-thyrometabolic disorders may cause abnormal free T4 levels. Anticonvulsant drug therapy (particularly phenytoin) may result in decreased free T4 levels due to an increased hepatic metabolism. Lithium and iodide preparations lower FT4 levels.

Patients on heparin therapy may have elevated free T4 levels due to release of non-esterified fatty acids, this can alter the relationship between free and bound hormones.

For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Chippewa Falls ​​Monday through Friday ​​Less than 2 hours ​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Diagnostic Treatment Center ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Eau Claire ​​Monday through Sunday ​​Less than 2 hours Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Flambeau Hospital ​Monday through Sunday​ ​​Less than 2 hours Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Ladysmith Medical Center ​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Lakeview Medical Center ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Marshfield ​Monday through Sunday ​Less than 2 hours Competitive Immunoassay using Direct Chemiluminescent Technology/Siemens Centaur
Merrill​ ​​Monday through Saturday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Minocqua ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
Stevens Point​ ​Monday through Friday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
Wausau​ ​​Monday through Sunday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
​Wisconsin Rapids ​Monday through Friday ​​Less than 2 hours ​​Enzyme Immunoassay, Homogeneous Sandwich Chemiluminescent Immunoassay/Siemens Dimension
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
84443​ ​1 ​TSH
​84439 ​1 ​Free T4 ​if needed
For most current information refer to the Marshfield Laboratory online reference manual.