The Pulse Of Veterinary Medicine

Vet-To-Vet Conversation With IDEXX

New research shows in-house total T4 test as accurate as reference laboratory testing

Given that thyroid disease is common, especially in older pets, and the clinical signs sometimes subtle, it’s typically recommended to include total T4 (TT4) in chemistry profiles for all cats greater than seven years of age and for dogs with any hint of hypothyroidism. Furthermore, patients receiving therapy for thyroid disease require frequent monitoring of TT4. No matter how you look at it, TT4 is a frequently run, essential test.

Despite the demand for thyroid testing, the share of chemistry profiles containing total T4 run in-house, on analyzers, such as the Catalyst Dx® and Catalyst One® chemistry analyzers, is much lower than the share sent to the reference laboratory. The reference laboratory is a wonderful resource, to be sure, but when tests aren’t performed in-house that could be, the customer experience suffers, and patients miss out on real-time results that could lead to the right treatment, sooner. 

And now, new research slated for publication in the Journal of Veterinary Internal Medicine shows that in-house TT4 testing can be as accurate as reference laboratory testing.1,2 Two prestigious groups just presented their favorable evaluations of the Catalyst® Total T4 Test to the congress of the European College of Veterinary Internal Medicine (ECVIM Congress 2016). Both studies, one coauthored by researchers from IDEXX and Purdue University and the other coauthored by researchers from IDEXX and the Animal Endocrine Center in New York City, show excellent correlation of the Catalyst Total T4 Test to the method used at the reference laboratory. What’s better than one research group demonstrating excellent performance? Answer: two!

In fact, the new Catalyst Total T4 Test was designed to match the performance of reference laboratory testing, and these peer-reviewed abstracts confirm that our design specifications are delivering in practice, at the point of care.

In addition to increased accuracy, the new Catalyst Total T4 Test was designed to address other pain points we heard from veterinarians and technicians surveyed in our product development research. 

  1. It’s got to be load-and-go.
    Nobody likes running a separate test or rotor to add TT4 to the profile. So, for the Catalyst Total T4 Test, we designed a slide that could be simply added to the top of any chemistry profile, “topping off” your profile, if you will—no second sample and no second work flow. 
  1. Out-of-range results are frustrating—and not very useful.
    Many other in-clinic TT4 tests have a limited dynamic range. That means for many tests, rather than receiving an easy-to-read, specific value, you’d get a frustrating greater than (>) or less than (<) sign—and nobody likes those! Out-of-range results hinder patient monitoring because it is hard to determine the trend for that patient. In response, for the Catalyst Total T4 Test, we made a reportable range to be as wide as what is encountered in the reference laboratory.
  1. It must be robust.
    Compromised samples, with lipemia, icterus, and hemolysis, are all too common in real life. The test must continue to report accurate results with as many of these samples as possible. The unique design of the Catalyst slide means this is a test that stands up to the sort of imperfect samples that are inevitable day-to-day.

 The Catalyst Total T4 Test is easy-to-use and delivers accurate and reliable TT4 results over a wide, clinically useful range, providing results comparable to those obtained by a veterinary reference laboratory. For more information on the Catalyst Total T4 Test, contact your IDEXX Veterinary Diagnostic Consultant. 


  1. Wolff E, Bilbrough G, Moore G, Lynn L, Murphy R, Scott-Moncrieff C. A side-by-side comparison of two assays for measuring canine and feline total thyroxine (TT4) [abstract ESVE-P-7]. J Vet Intern Med. In press.
  2. Peterson ME, Rishniw M, Bilbrough GE. Validation of an in-clinic point-of-care immunoassay for measurement of total thyroxine (TT4) concentration in serum from euthyroid and hyperthyroid cats [abstract ESVE-P-1]. J Vet Intern Med. In press.

Graham Bilbrough

Graham Bilbrough

After graduating from the University of Cambridge, Dr. Bilbrough spent a year in mixed practice in Oxfordshire, England, before returning to Cambridge to become the British Small Animal Veterinary Association (BSAVA) Petsavers resident in anesthesia and critical patient care. Later he became the senior anesthetist at the Queen’s Veterinary School Hospital, responsible for the clinical anesthesia service and intensive care unit. Dr. Bilbrough joined IDEXX UK in October 2006, and after working for IDEXX across Europe, he moved to the Westbrook, Maine, headquarters, where he is a medical affairs manager.

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