Thyroglobulin, Tumor Marker, Fine-Needle Aspiration (FNA)-Needle Wash, Lymph Node
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
An adjunct to cytologic examination of fine-needle aspiration specimens in athyrotic individuals treated for differentiated thyroid cancer, to confirm or exclude metastases in enlarged or ultrasonographically suspicious lymph nodes
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Thyroglobulin, FNA, Lymph Node
Specimen Type Describes the specimen type needed for testing
Fine Needle Wash
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: Sterile vial
Collection Instructions: After collection of the cytology specimens and expulsion of the material for smear or CytoTrap processing:
1. Wash/rinse each FNA needle from a single lymph node nodule with 0.1 to 0.5 mL of normal saline.
2. Pool each wash from a single lymph node nodule into 1 vial. If more than 1 nodule is biopsied, each nodule biopsy should be submitted as a separate specimen.
3. Inspect the specimen as follows:
a. If the specimen shows visible blood or tissue contamination, centrifuge the specimen. Transfer the supernatant to a new plastic vial. Freeze specimen.
b. If specimen is clear, freeze specimen in plastic vial.
Additional Information: If multiple lymph node testing is needed, submit each under a separate order. Clearly identify each specimen.
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.
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Fine Needle Wash||Frozen (preferred)||7 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Thyroglobulin (Tg) is a 660,000 molecular weight glycoprotein produced exclusively by the follicular cells of the thyroid. It is secreted into the follicular lumen, where it serves as the precursor of, and storage reservoir for, thyroxine (T4) and triiodothyronine (T3). T4 and T3 are released after Tg is endocytosed and proteolytically degraded in the thyrocyte. Since Tg is produced only by follicular thyrocyte-derived cells, measurement of serum Tg levels in athyrotic patients enables detection of persistence, recurrence, or metastasis of differentiated thyroid carcinoma. In addition, because of the thyroid specificity of Tg, its measurement in biopsy specimens of nonthyroidal tissues may assist in confirming and localizing metastatic disease.
In the most common type of thyroid cancer, papillary thyroid carcinoma (PTC), >80% of all thyroid cancer cases, most metastatic disease occurs in loco-regional lymph nodes in the neck, which are easily examined by ultrasound. Most suspicious nodes undergo ultrasonography-guided fine-needle aspiration (FNA) cytology to determine a diagnosis. Unfortunately, in up to 20% of the specimens, inadequate cellularity or nonrepresentative sampling precludes the diagnosis.
Several studies have reported that the detection of Tg in fine needle aspiration (FNA)-needle washes improves the evaluation of suspicious lymph nodes in patients with differentiated thyroid carcinoma.(1-3) A recent study reported that a Tg cutoff of 1 ng/mL for FNA-needle wash specimens provided 100% sensitivity and 96.2% specificity for the detection of metastatic thyroid carcinoma in lymph nodes.(3) The diagnostic performance of needle wash Tg at the 1-ng/mL cutoff compared favorably with cytology (95.1% overall agreement) and allowed accurate diagnosis in 18 of the 19 cases in which cytology was nondiagnostic or not performed.(3) Additionally, when measuring Tg in FNA-needle wash specimens, the clinical performance of FNA Tg is unaffected by the presence of Tg antibodies, a frequent problem when measuring Tg levels in serum.
Cytologic examination and measurement of Tg can be performed on the same specimen. To measure Tg, the FNA needle is rinsed with a small volume of normal saline solution immediately after a specimen for cytological examination has been expelled from the needle for a smear or CytoTrap preparation. Tg levels are measured in the needle wash.
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 =1.0 ng/mL
This cutoff has been validated for total needle wash volumes of < or =1.5 mL of normal saline. If wash volumes are substantially larger, a lower cutoff might apply.
In athyrotic patients with a history of differentiated thyroid carcinoma, a fine-needle aspiration (FNA)-Tg value >1.0 ng/mL suggests the presence of metastatic differentiated follicular cell-derived thyroid carcinoma in the biopsied area.
FNA-Tg measurements yield reliable results in most cases with nondiagnostic cytology, and are approximately equal in diagnostic accuracy to cytological examinations that are deemed sufficient for diagnosis.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Fine-needle aspiration (FNA)-Tg should not be used to screen asymptomatic individuals for neoplastic disease.
This test has been validated only in single lymph nodes from athyrotic patients. While the needle washes from several distinct needle passes or aspirations from a single node should be pooled, biopsies from different nodes should be submitted as separate specimens.
For specimens from other sources, contact Mayo Medical Laboratories.
Do not interpret FNA-Tg levels as absolute evidence of the presence or absence of malignant disease. Results should be used in conjunction with information from the clinical evaluation of the patient, cytology, and imaging procedures.
Immunometric assays can, in rare occasions, be subject to interferences such as "hooking" at very high analyte concentrations (false-low results) and heterophilic antibody interference (false-high results). If the clinical picture does not fit the laboratory result, these possibilities should be considered. While autoantibody interference (typically false-low results in immunometric assays) is reported to not be an issue in FNA-needle wash specimens, the report was based on a small number of cases; therefore, the possibility of autoantibody interference should also be considered.
Results are dependent on accurate sampling and a maximum needle wash volume of < or =1.5 mL.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Pacini F, Fugazzola L, Lippi F, et al: Detection of thyroglobulin in fine needle aspirates of nonthyroidal neck masses: a clue to the diagnosis of metastatic differentiated thyroid cancer. J Clin Endocrinol Metab 1992;74(6):1401-1404
2. Frasoldati A, Toschi E, Zini M, et al: Role of thyroglobulin measurement in fine-needle aspiration biopsies of cervical lymph nodes in patients with differentiated thyroid cancer. Thyroid 1999;9(2):105-111
3. Snozek CL, Chambers EP, Reading CC, et al: Serum thyroglobulin, high-resolution ultrasound, and lymph node thyroglobulin in diagnosis of differentiated thyroid carcinoma nodal metastases. J Clin Endocrinol Metab 2007;92(11):4278-4281
Method Description Describes how the test is performed and provides a method-specific reference
For Mayo Clinic patients, any visibly blood-tinged samples are spun in a clinical centrifuge, and the supernatant is used for testing. If there is no visible blood contamination, the sample is used directly. Mayo Medical Laboratories specimens should be evaluated for hemolysis before submission.
The saline needle-wash specimen is analyzed with the Beckman Access thyroglobulin (Tg) assay, a simultaneous 1-step immunoenzymatic (sandwich) assay performed on the Beckman Coulter UniCel DxI 800. A sample is added to a reaction vessel along with a biotinylated mixture of 4 mouse monoclonal anti-Tg antibodies, streptavidin-coated paramagnetic particles, and mouse monoclonal anti-Tg antibody-alkaline phosphatase conjugate. The biotinylated antibodies and the sample Tg bind to the solid phase, while the conjugate antibody reacts with a different antigenic site on the Tg molecule. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field, while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos*530 is added to the vessel and light generated by the reaction is measured with a luminometer. Light production is directly proportional to the concentration of Tg in the sample. The amount of analyte in the sample is determined from a stored, multipoint calibration curve.(Instruction manual: Access Thyroglobulin Assay. Beckman Coulter, Inc., Fullerton, CA, 2010)
For all samples with Tg concentrations >1.0 ng/mL, a dilution series is performed. A linear dilution excludes hooking and most major interferences. Samples that contain Tg < or =1.0 ng/mL are spiked with exogenous Tg to identify possible interferences that may cause a false-low result.
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 Friday; 5 a.m.-12 a.m., Saturday; 6 a.m.-6 p.m.
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.
Same day/1 day
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.
This test has been modified from the manufacturer’s instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.
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.
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|
|TGFN||Thyroglobulin, FNA, Lymph Node||53920-5|