CTDS News

We are pleased to announce that we have achieved Horse Race Betting Levy Board approval for Equine CEM testing. Please contact the laboratory or visit www.ctdslab.co.uk/cem.html for details of our CEM and EVA testing packages in preparation for the 2005 season.

Common clinical signs of hypothyroidism in dogs include weight gain, lethargy, reduced exercise tolerance and poor coat quality. However, the disease affects almost all body systems and as a result a wide variety of signs can potentially be associated with this endocrinopathy.
Diagnosis is complicated by the fact that many non-thyroidal illnesses (NTI) may present with similar features to hypothyroidism and can result in reduced thyroid output. There is no perfect lab test for the diagnosis of hypothyroidism and the available alternatives all have their own strengths and weaknesses that need to be taken into account. Often the best approach is to use multiple tests that complement one another and help to improve diagnostic accuracy.

Where hypothyroidism is a consideration, making the diagnosis requires three distinct steps:

1. Exclude non-thyroidal illness (NTI).

By excluding other disease conditions first the predictive value of the thyroid tests will be significantly increased. In practical terms this phase may include a profile including FBC and smear evaluation and where necessary screening tests for Cushings. The latter can be important as both endocrinopathies can result in alopecia, weight gain and marked reductions in T4.

2. Run a screening test for hypothyroidism.

Basal T4 is sensitive but not specific for hypothyroidism. As a result, a clearly normal T4 reliably excludes hypothyroidism in almost all cases. Basal T4 is included in the CTDS Canine Endocrine Profile. While almost all dogs with hypothyroidism have a reduced basal T4, many dogs with NTI have low T4 also. To help improve the specificity of T4 it is often coupled with TSH assay. T4 with TSH works well as a relatively low cost screening test for hypothyroidism and can be run alongside or following the endocrine profile.

3. Run a thyroid function test or panel.

This is indicated where screening tests give equivocal results. Thyroid function panels combine T4 and TSH with Free T4 by dialysis and a test for thyroglobulin autoantibodies (which are highly associated with the presence of lymphocytic thyroiditis, the cause of around 50% of cases of hypothyroidism). Thyroid panels originated in the US and some labs still send samples there for testing. At CTDS all the assays are performed either in house or within the UK so turnaround times are much quicker (1 week) and analytical quality can be assured.
Once the diagnosis is made therapeutic monitoring is helpful both to avoid iatrogenic hyperthyroidism and to identify cases where unusual T4 uptake or metabolism results in low serum levels, despite adequate oral doses.
Ideally T4 is assayed on samples obtained 4-6 hours post pill. Where dogs appear to respond poorly to supplementation it can be useful to obtain a further pre-pill sample to evaluate trough T4 concentrations and to include TSH with T4.

Monitoring Thyroid Treatment

Soloxine (Arnolds) is the only licensed veterinary preparation of levothyroxine. Dose is normally 20ug/kg given twice daily. Total T4 levels should be monitored after 1 month of therapy, with a sample being taken 4 - 6 hours post-pill. Ideally Total T4 levels should be above 50 nmol/L at this time point.

Allergic Skin and Gastrointestinal Disease

CTDS is pleased to be able to offer an expanded range of diagnostic tests for the investigation of suspected allergic skin and gastrointestinal disease. The assays utilised are based on the detection of allergen specific IgE, detected by monoclonal antibodies, using carefully controlled and validated ELISA systems. From the 1 st November 2004 we have increased the range and nature of the tests on offer, with further developments in the pipeline. These test methods ensure that there is a virtually complete correlation between the results of the screening test and the expanded panels which makes the use of screening tests for cats and dogs more attractive than before.
By using the screen, the absence of allergen specific IgE can be reliably detected at a lower cost, whilst animals with a positive screening test can be taken forward to a full panel with a greater confidence of gaining significant results.

CTDS Allergy Tests for both Cats and Dogs

Test Name	Dog	Cat	Test Code	Sample	Cost exc VAT
Environmental & Food Screen	Yes – New	Yes – New	S69	3ml serum	£37.50
Food Panel	Yes	Yes – New	S64	2ml serum	£75
Environmental Panel	Yes	Yes	S63	2ml serum	£75
Food & Environmental panel	Yes	Yes – New	S65	3ml serum	£145

Please contact the laboratory if further information is required or to discuss any potential allergy cases you may have. Further information on CTDS allergy tests may be found at www.ctdslab.co.uk/allergy.html or as a flyer available from the lab.

We would like to wish you all a very merry Christmas!

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