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Why We Use a Purple Top Tube for Mammal CBCs

A purple top tube with 500uL of whole blood to run a mammal CBC on the Advia
A purple top tube with 500uL of whole blood to run a mammal CBC on the Advia
October 10, 2022

By Shannan Seely

If you’re wondering why a reference lab that got its start imaging slides of avian and reptile blood is asking for a purple top tube for mammal blood, you’re not alone. It’s a good question: Why does a reference lab that uses automated microscopy need whole blood in a purple top tube to run a slide through a microscope?

The simple answer is redundancy. The complicated answer is to hone the image-based approach for high throughput CBCs so you get more actionable data. Here’s how that works.

For every mammal CBC, Moichor uses the blood samples provided in a purple top tube to perform flow cytometry and AI-assisted morphology assessment.

According to Moichor Director of Clinical Medicine, Bianca Murphy, DVM, DABVP the redundancy continuously hones the CBC imaging software enabling accuracy and cell recognition not possible with flow cytometry alone. 

“We run every sample through the Advia before it goes on a slide,” Dr. Murphy said. 

For nearly two and a half decades, the industry gold standard for high-throughput hematology analyzers for mammal CBCs has been the Advia. This is the device used by all of the larger reference labs. 

But despite being the standard for the high-throughput counting of cells, flow cytometry is unable to recognize toxicity, inclusions, parasites, and immaturity of cells — these have to date, only been recognizable through the eyes of a pathologist.

What started as an innovation for Avian and Reptile CBCs

In birds and reptiles, every single red blood cell is nucleated. The benchtop hematology analyzers cannot detect the difference between the red and white blood cells on these blood samples.

According to Moichor Director of Pathology Kyle Lauren Webb, DVM, DACVP, when it comes to avian and reptile hematology, pathologists are using the same practices applied since the beginning of veterinary medicine because of the limitations of high-throughput hematology analyzers.

Bird and reptile laboratory medicine has always relied on manual assessments, Dr. Webb explained. Most laboratories perform avian and reptile CBCs by doing counts manually in a hemocytometer. Several techniques can be used, but have drawbacks, which directly affect the accuracy of results. A study on owl CBCs collections showed that, depending on the method used for the manual hemocytometer, the counts may vary considerably.1 

“There’s no true gold standard for birds and reptiles to get accurate CBC results as compared to mammals,” Dr. Webb said. 

Moichor’s approach has been to automate each of the steps a pathologist would apply, but using software and imaging to capture the cells with a microscope and computer vision, a subset of artificial intelligence to identify, classify and analyze each of the cells.

“We can count more cells than a human being can possibly count at one time and still be efficient and accurate,” Dr. Webb said. “We now have a high throughput way of counting cells that uses the same approach as a pathologist.”

Why this is now significant for mammal CBCs

What started out as a solution for avian and reptile veterinarians, is now changing what small animal practices are able to achieve with a CBC.

“Flow cytometry has long been the status quo for small animal practices,” Dr. Murphy said. “As a result, clinicians request images and only ask for a pathology review when CBC results point to a deeper underlying problem.”

“Our goal is to continuously assess and optimize our image-based approach to match the high-throughput cell counting capabilities of the Advia with the morphology-recognition capabilities of a pathologist,” Dr. Webb said “And we’re building this image-based CBC to be high throughput in a way that would not be possible for a human being,” she said. “ And that’s why we need a 1000uL in a purple top tube for our small animal samples.”

Submitting a CBC in a purple top tube allows us to provide both accurate cell counts and morphology with the use of two separate methodologies. 

Specimen requirements

To achieve optimum results for a small animal CBC, we request the following: 

  • Minimum 1000uL of whole blood in a purple top tube*

For more on our requirements, Check out this link to our test menu

Want to know more about how AI works for diagnostics testing? Check out this article on how the Moichor artificial intelligence works.

*This test can be run with an absolute minimum of 500uL

Reference

1. Ammersbach, M., Beaufrère, H., Gionet Rollick, A., & Tully, T. (2015). Laboratory blood analysis in Strigiformes—Part I: hematologic reference intervals and agreement between manual blood cell counting techniques. Veterinary Clinical Pathology, 44(1), 94–108. https://doi.org/10.1111/VCP.12229.

Education
/
Hematology
/

Why We Use a Purple Top Tube for Mammal CBCs

If you’re wondering why a reference lab that got its start imaging slides of avian and reptile blood is asking for a purple top tube for mammal blood, you’re not alone. It’s a good question: Why does a reference lab that uses automated microscopy need whole blood in a purple top tube to run a slide through a microscope?

October 10, 2022
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