Blood tests and reference ranges






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Reference ranges:


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Blood tests


The following links provide information about blood tests commonly performed to diagnose thyroid conditions or to monitor their treatment. This information may also help understanding the results of these tests.


Other tests that are sometimes performed are:


Reference ranges


The reference ranges for thyroid function tests in New Zealand differ from one laboratory to the other. It is important to keep in mind when interpreting blood test results, that thyroid hormone levels are known to be influenced by factors such as age, sex, ethnicity, diet, genetics, and the presence of thyroid autoimmunity. Interpreting blood test results is, therefore, not as straightforward as is sometimes suggested. For that reason, it is recommended not to diagnose and treat thyroid disease based on laboratory test results alone but instead to treat patients individually based on their individual signs, symptoms and test results.


These are the reference ranges (for adults) currently used by some New Zealand laboratories:


Thyroid Stimulating Hormone

Alternative name: Thyrotropin


Laboratory guidelines

TSH reference ranges (adults)

Last updated

LabPlus Test Guide (Auckland)

0.27 - 4.2 mU/L

19/11/2015

Labtests (Auckland)

0.3 4.0 mIU/L

14/12/2015

Waikato Health Laboratories (Waikato)

0.27 4.2 mIU/L

05/05/2015

Wellington SCL Test Guide

0.4 3.8 mU/L

18/03/2015

SIQAG Biochemistry Reference Intervals version 1.5 (South Island, Hawke's Bay, Taranaki)*

0.4 4 mIU/L

22/12/2011


 

Free T4

Alternative names: FT4, Thyroxine free

Note: Total T4 is generally not tested in New Zealand

Laboratory guidelines

Free T4 reference ranges (adults)

Last updated

LabPlus Test Guide (Auckland)

12 22 pmol/L

19/11/2015

Labtests (Auckland)

10 20 pmol/L

14/12/2015

Waikato Health Laboratories (Waikato)

12 22 pmol/L

05/05/2015

Wellington SCL Test Guide

12.8 20.4 pmol/L

18/03/2015

SIQAG Biochemistry Reference Intervals version 1.5 (South Island, Hawke's Bay, Taranaki)*

10 24 pmol/L

22/12/2011


 

Free T3

Alternative names: FT3, Triiodothyronine free

Note: Total T3 is generally not tested in New Zealand

Laboratory guidelines

Free T3 reference ranges (adults)

Last updated

LabPlus Test Guide (Auckland)

3.9 6.8 pmol/L

19/11/2015

Labtests (Auckland)

3.0 6.5 pmol/L

14/12/2015

Waikato Health Laboratories (Waikato)

3.1 6.8 pmol/L

05/05/2015

Wellington SCL Test Guide

4.0 6.8 pmol/L

18/03/2015

SIQAG Biochemistry Reference Intervals version 1.5 (South Island, Hawke's Bay, Taranaki)*

2.5 6.0 pmol/L

22/12/2011


 

Thyroid Antibodies

Alternative names: Anti Microsomal Antibodies, Anti Thyroid Peroixidase Antibodies (Anti-TPO, TPO-Ab), Anti Thyroglobulin Antibodies (Anti-Tg, TgAb)

Note: Even at low levels, Anti Thyroglobulin Antibodies may interfere with Thyroglobulin measurement to cause falsely low or undetectable Thyroglobulin (Tg) levels. This is important for thyroid cancer patients who have had a total thyroidectomy and whose serum Thyroglobulin should be undetectable (<0.1 g/L).

Laboratory guidelines

Thyroid Antibodies reference ranges (adults)

Last updated

LabPlus Test Guide (Auckland)

Anti-TPO (standard thyroid antibodies test)
Negative: < 34 IU/mL
Weak positive: 35-60 IU/mL
Positive: > 60 IU/mL

Anti-Tg (only if specifically requested)
Negative: < 115 IU/mL
Abnormal: > 115 IU/mL

24/03/2015

Labtests (Auckland)

Normal: < 60 U/mL

14/12/2015

Waikato Health Laboratories (Waikato)

Negative: < 5 IU/mL (Anti-Tg); < 6 IU/mL (Anti-TPO)

21/02/2014

Wellington SCL Test Guide

Negative: < 6 IU/mL
Weak positive: 6 - 200 IU/mL
Moderate positive: 201 - 500 IU/mL
Strong positive: > 500 IU/mL

22/09/2015

Canterbury Health Laboratories (Canterbury)

Negative: < 10 IU/mL
Weak positive: 10 - 200 IU/mL
Moderate positive: 201 - 500 IU/mL
Strong positive: > 500 IU/mL

 


 

Thyroid Stimulating Antibodies

Alternative names: Thyroid Stimulating Immunoglobulin (TSI), Anti TSH Antibodies, Thyroid Receptor Antibodies (TRA), TSH Receptor Antibodies, Long Acting Thyroid Stimulator (LATS)

Laboratory guidelines

Thyroid Stimulating Antibodies reference ranges (adults)

Last updated

LabPlus Test Guide (Auckland)

Negative: < 1.75 IU/L
Abnormal: > 1.75 IU/L

24/03/2015

Waikato Health Laboratories (Waikato)

Negative: < 1.3 IU/L
Borderline: 1.3 - 1.7 IU/L

21/02/2014

Wellington SCL Test Guide

Negative: < 1.0 IU/L
Indeterminate: 1.0-1.75 IU/L
Positive: > 1.75 IU/L

14/10/2015

Canterbury Health Laboratories (Canterbury)

Negative: < 1 U/L
Borderline Positive: 1-1.5 U/L
Positive: > 1.5 U/L

 


*SIQAG= South Island Quality Assurance Group for Biochemistry and Haematology (agreed with: Canterbury Health Laboratories, Southern Community Laboratories, Medlab South and West Coast DHB. Also consulted: Hawke's Bay DHB and Taranaki DHB)



   


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