Evaluating blood, urine and feces (as well as other bodily fluids) to screen for and monitor disease processes is an essential component of animal healthcare. Samples can be submitted to any number of veterinary reference laboratories, gold-standard facilities with board-certified veterinary clinical pathologists and well-trained medical technologists who work with test samples all day. According to the American Animal Hospital Association, more than 60% of complete blood counts (CBC) and biochemical profiles (CHEM) are sent to veterinary reference laboratories. But some tests, including CBCs and CHEMs, can be performed in veterinary hospitals, a practice commonly referred to as in-house laboratory testing.
So which is better: a veterinary reference laboratory or an in-house laboratory?
I continuously strive to provide my patients and their families with the best – the best medicine(s), the best treatment(s) and of course, the best testing modalities! To achieve the latter, I always perform non-STAT tests at a veterinary reference laboratory. Why? I trust them. These testing facilities are accredited by the American Association of Veterinary Laboratory Diagnosticians (AAVLD). Simply, I want a board-certified veterinary clinical pathologist overseeing my patient’s samples. And let’s be honest. Almost all in-hospital laboratories would be shut down if they were regulated by the same standards required by the AAVLD. Some states even have laws that prohibit professionals from both prescribing tests and owning the laboratory where testing is conducted.
In the interest of presenting a balanced discussion, let’s look at the major advantages and disadvantages of in-house and reference laboratory testing as it applies to CBCs and CHEMs, two of the most common tests performed in veterinary medicine.
Complete blood count (CBC)…
Complete blood counts are performed on machines called hematology analyzers, and the most commonly cited reasons for using in-house analyzers are ease of use and rapid turn-around of results. The three most commonly used analyzers in clinical practice are:
Impedance technology analyzers: This type of analyzer relies on electrical conductance to count cells and estimate cell size; a decrease in conductance is directly proportional to cell volume. Based on a study by Pinches et al (In Pract, 2006), this technology is reasonably accurate for overall red blood cell (RBC) and white blood cell (WBC) counts, but not so for platelet counts, RBC size, and counting different types of WBCs (called a differential).
Quantitative buffy coat analyzers: Using this analyzer, cells are separated via centrifugation and the heights of each cell layer are measured. For accuracy, this technique requires distinct separation of cell layers, but incomplete separation occurs quite frequently. A study by Bienzle et al (Vet Clin Pathol, 1999) demonstrated WBC differential results were unreliable.
Laser flow cell counter: A laser is used to count cells based on the principle that different cells reflect laser light at different angles. Evaluation of WBCs and platelet counts are less accurate.
Regardless of the type of analyzer used, a microscopic blood film examination is an absolutely essential part of a CBC. Despite this fact and in my experience, this recommended component is often not performed in primary care veterinary practices. Two most commonly cited reasons from primary care doctors for omitting a blood film evaluation are lack of confidence performing a blood film assessment and lack of time to perform the evaluation. Veterinary reference laboratories are not allowed to omit this step! If veterinary reference laboratories can’t omit peripheral blood film evaluations, then veterinarians performing CBCs in their in-house laboratories can’t omit them either!
Biochemical Profile (CHEM)…
Without question the major advantage of in-house laboratory testing is that they provide potentially life-saving information rapidly. But the main disadvantage is their often-profound inaccuracy. Indeed most human medical offices have moved away from using in-house analyzers because of this inaccuracy and fear of litigation. Veterinarians should consider this, as in-house laboratory test results may not stand up in a court of law. Minimally veterinarians should be able to provide documentation that regular quality control samples are evaluated in their in-house laboratories.
Some veterinarians will still maintain in-house testing is just fine; they cite numerous arguments for such testing over the use of veterinary reference laboratories, including:
“Pet parents demand rapid turn-around”
As one who rarely uses in-house laboratory equipment, I wholeheartedly disagree with this argument. In my experience over the past almost 12 years as a veterinarian, I’ve never had a pet parent base his/her treatment decisions on where a test was performed.
“If the in-house machine documents an abnormality, I’ll just confirm it by sending another sample to a reference laboratory.”
This rationale has never made much sense to me. Knowing one is going to recheck any abnormality from an in-house test at a gold-standard laboratory implies one actually doesn’t trust the in-house machine in the first place. It also implies one does trust the reference laboratory. So why not send it there in the first place?
“In-house testing is ideal for same-day pre-anesthesia screening.”
Pet parents, like veterinarians, are profoundly concerned about anesthesia safety, and one should never be in a rush in a non-emergency scenario to sedate a patient or place one under general anesthesia. Isn’t it better to collect blood samples in advance and have a board-certified clinical pathologist oversee testing? When testing occurs prior to the day of anesthesia, two things may happen:
- Normal laboratory results reassure pet parents and reinforce the tenet that there are pertinent issues that might affect the safety of a patient.
- Abnormal results lead to follow-up diagnostic investigation that could save lives.
Veterinary reference laboratories aren’t perfect…
The use of veterinary reference laboratories is not without potential problems, most notably:
- Sample transport
- Delay between sample collection and performing a test
- Loss of samples during transit
- Inadequate sample storage
At these sites technical and human errors can still occur, so one should not simply assume results are faultless. But a major difference from an in-house laboratory is the on-site availability of medical technologists and board-certified clinical pathologists that can expeditiously address quality assurance issues and provide invaluable insight regarding test results.
The take-away message about laboratory tests…
As a board-certified internal medicine and emergency/critical care specialist, I regularly consult about patients for whom in-house laboratory data was misleading or wrong. If I have the time to wait for results, I’d much rather get my results for a veterinary reference laboratory where the machines are better than in-house ones and quality control is certainly more assured.
To learn more about the Association of Veterinary Laboratory Diagnosticians, click here.
To learn more about board-certified veterinary clinical pathologists, please click here.
Wishing you wet nosed kisses,