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Tshblockabserqlcbaifa

Published: August 9, 2026Updated: August 16, 2026

A blood test that detects antibodies blocking thyroid hormone production.

Quick summary

{"Measures antibodies that prevent TSH from stimulating the thyroid","Helps diagnose certain thyroid disorders","Performed on a blood serum sample"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
99078-8
Short code
TSH blocking Ab
Synonyms
TSH Block Ab Ser Ql CBA IFA
Category
cardiac
Sample
serum
Container
Serum separator tube (SST) or plain red top tube
Units
N/A
Ref low
0
Ref high
100
Critical range
0.1 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
cba-ifa
CPT
84443
SNOMED
118772009
Specimen volume
1.0 mL serum minimum (2.0 mL recommended)
Stability
Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C or below): 30 days
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
72–168 hours
Order
routine

What is this test?

The TSH Blocking Antibody test detects whether your blood contains antibodies that block the action of thyroid-stimulating hormone (TSH). Normally, TSH signals your thyroid gland to produce thyroid hormones. When blocking antibodies are present, they interfere with this process, potentially causing thyroid dysfunction.

How is it performed?

A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where specialists use a cell-binding immunofluorescence assay to detect the presence of these blocking antibodies in your serum.

Why might I need this test?

Your doctor may order this test if you have symptoms of thyroid dysfunction that cannot be fully explained by routine thyroid tests. It is particularly useful in evaluating patients with unusual thyroid function results or those who do not respond to standard treatments.

Reference range

Negative: <1:100 titer; Positive: ≥1:100 titer (laboratory-specific reference range)N/A

Specimen: serum

No special preparation required. This test does not require fasting.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Do I need to fast before this test?
No fasting is typically required for this blood test. However, always follow your doctor's specific instructions.
What do 'Present' results mean?
'Present' means TSH blocking antibodies were detected in your blood, which may indicate an autoimmune condition affecting your thyroid function.
Is this test painful?
You may feel a brief sting when the needle is inserted, but the procedure is generally well-tolerated.
How long does it take to get results?
Results are typically available within a few days to a week, depending on the laboratory.
  1. 1
    MedlinePlus - Thyroid TestsSource
  2. 2
    American Thyroid AssociationSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy