The following FAQ section is a quick reference for some of the most frequently asked questions related to in-house diagnostic technology, sample handling techniques, and quality control recommendations. This information will help ensure you get accurate patient results every time.

General

What risk am I taking if I run my analyzer using expired reagents?

Many customers run their analyzers using reagents that have recently expired, and claim they don’t see a difference in their results. While an analyzer may seem to operate normally when using outdated reagents there is no assurance the results are accurate. Best practices state reagent use should be restricted to the dates defined by the manufacturer. Usage beyond the expiration date puts a patient at risk because the generation of erroneous data may lead to an incorrect and potentially harmful diagnosis. Extended use of expired reagents may also cause damage to the instrument.

My vendor keeps promoting that I should be running a daily quality control. Is this step necessary?

Yes, according to ASVCP guidelines all instruments should have controls run routinely, even systems with internal calibrators. A commitment to consistently repeatable and accurate results involves regular monitoring using commercially available control materials with known target values. Quality control (QC) is needed to verify instrument performance, reagent performance, and operator performance; in essence, the entire system. It is strongly recommended, especially with hematology, that controls be run daily and be documented to note trends and inconsistencies before they present result inaccuracies.

I am considering using in-house lab analyzers to generate my lab results, but I am concerned that my staff will have less time with our clients. Are there easy ways to manage my technicians’ time?

A staff well-versed in the importance and value of blood work can improve your patient care, as well as your customer service. Staff members educated in basic hematology and chemistry can detail the benefits of evaluating patients’ organs, organ systems and general metabolic state whether it is part of an annual exam, related to illness, or as a pre-anesthetic assessment. With in-house analyzers, you can respond more quickly with diagnostic treatment decisions, even before your patient and client leave your clinic. In addition to investing in your practice with quality lab instruments, find a vendor who can fully support the needs of your staff through adequate training, educational resources, instruction on best practices, and instrument service. Incorporation of in-house analyzers will improve your quality of patient care, customer service and your clinic bottom line.

Hematology

My vendor keeps promoting that I should be running a daily quality control; is this step necessary?

Yes, according to ASVCP guidelines, all hematology instruments should have controls run routinely, even systems with internal calibrators. A commitment to consistently repeatable and accurate, quality results involves regular monitoring using commercially available control materials with known target values. Quality control (QC) is needed to verify instrument performance, reagent performance, and operator performance. It is strongly recommended that controls be run daily and be documented to note trends and predict out of control situations before they present result inaccuracies.

How long do we really have to mix an EDTA sample before we run a CBC?

The answer depends on how quickly the sample will be analyzed and the type analyzer your clinic owns. If your sample was collected into an EDTA tube, inverted several times, and will be analyzed within 5 minutes of collection it may only require 1 minute of mixing (if using the HemaTrue® Analyzer). If you are uncertain when you will be analyzing your sample and the sample has not been on a blood rocker Heska recommends the following: • Small animal samples should mix for a minimum of 2 minutes in the on-board tube mixer (if using the HemaTrue analyzer) or other mixer. • Equine samples should mix for a minimum of 3 minutes. When in doubt, it is important to remember that a sample cannot be mixed too long.

I recently went to a conference and heard repeatedly that we should be checking our CBC samples for microclots; how do we do it and why should we care?

Proper sample collection and handling is the most important step in obtaining accurate results on an automated hematology analyzer. In particular, microclots can falsely decrease the platelet count and lower the WBC count due to cell trapping. Microclots can also cause obstructions in the analyzer requiring maintenance. To check for microclots, immerse 2 wooden applicators into the blood and swirl gently. Remove the sticks and examine them for small, dark red or white translucent particles (microclots). If clots are present, discard the sample and redraw.

We are trying to learn how to make blood films and aren’t sure what to change when we have a problem. What should we do when our film...

  • Is too thin? The motion of the pusher slide is too slow; increase the speed of the pusher slide.
  • Is too short? Either your blood drop is too small or the angle of pusher slide is too vertical. You need to either use a larger drop of blood or decrease the angle of the pusher slide.
  • Runs off the end of the slide? Your drop of blood is too large or the angle of pusher slide is too flat (too low). To correct this, use a smaller drop of blood or increase the angle of the pusher slide (i.e. make it more upright).
  • Has “skip” marks on the slide? There is either too much pressure being applied to the pusher slide or the slide is being pushed too slowly. You can try to apply gentle pressure while pushing the slide forward or push your slide a little faster.

We were concerned about the accuracy of our analyzers and called the company. During our conversation we found we were impacting our results by the way we handled our samples. What sample handling factors negatively impact the accuracy of our analyzers?

Poor technique during sample collection and improper sample handling (prior to analysis) can impact both hematology and chemistry results. We recommend the following steps to minimize the effects of poor sample handling technique: • Optimally, the patient is fasted for 12 hours before sample collection to prevent lipemia • Swift, atraumatic venipuncture is critical • Use a 22-gauge needle or larger to minimize hemolysis • Avoid repositioning the needle and/or excessive suction on the syringe to prevent microclot formation • Immediately transfer the blood sample into tubes with additive(s), then to clot or serum tubes • Remove the tube stopper and the needle from the syringe; fill tube directly from the syringe to ½ to ¾ full and recap the tube. An alternative is to push the needle through the stopper and allow the vacuum from the tube to aspirate the sample; do not press on the syringe plunger, this will cause hemolysis. • Gently invert any tube with additive 8 to 10 times to adequately mix the sample • Allow sample to stabilize preferably on a blood rocker • Prior to analysis, check the sample for microclots by immersing 2 wooden applicator sticks into the blood and swirling. Remove the sticks and examine for small, dark red or white translucent particles. If clots are present discard the sample and redraw from the patient.

Chemistry

We are looking to purchase a new chemistry analyzer and have noticed some analyzers are “dry chemistry” and some are “wet”. What’s the difference?

Liquid or “wet” chemistry analyzers are the most traditional chemistry system and are commonly used in high-volume reference labs. Sample is added to a liquid reagent which after a reaction over time produces a colored mixture. Light of a particular wavelength is passed through the solution, measuring the reflectance or absorbance of the color by a photodector. The degree of color change is directly or indirectly proportional to the concentration of the analyte or enzyme activity. Dry chemistry systems use reagent strips or slides, impregnated with chemistry reagents in a dried form. When a sample is applied to the reagent strip or slide, it triggers a reaction that results in color development. A photometer is then used to measure the amount of light absorbed or reflected from the surface. Both technologies will provide accurate results when a sample is collected and processed correctly and the analyzer is operated and maintained properly.

We have recently switched from serum to plasma for our chemistry samples. What’s the difference?

Serum is formed when a blood sample is allowed to clot to completion; this typically takes 15 minutes. The tube is then centrifuged to pack all cellular elements and clot, leaving a supernatant of serum. Plasma tubes typically have a form of heparin (preferably lithium heparin) added to the tube to prevent clot formation. When a blood sample is collected it can be immediately centrifuged to separate the cellular components from the plasma. Use of plasma samples allows for faster sample processing and will not impact your results if the tube is filled properly.

We are very careful in how we collect and process our samples, and yet we still sometimes get fibrin in our serum. How can we avoid this?

When blood is collected into a red-top tube contact with the glass initiates the clotting cascade, with the final step being the conversion of fibrinogen to fibrin. On occasion a sample may not complete this conversion in 15 minutes and fibrin may form after the serum has been separated from the red cells. This fibrin is viscous and can occlude pipette tips, displace fluid volume and ultimately cause erroneous laboratory errors. If fibrin is a common problem, the samples can be incubated in a water bath or incubator block at, or near, body temperature. This process will drive the fibrination to completion in less than 15 minutes. An alternative solution is to use plasma instead of serum.

We’ve been told that amylase in cats is useless for detecting pancreatitis so we don’t need to run it. Why is this?

The significance and usefulness of amylase varies from species to species. In cats with pancreatic injury amylase is not usually increased, and may actually be decreased. This behavior makes amylase an unreliable indicator of pancreatic injury in the cat.

We want to start running pre-anesthetic chemistry panels in-house but don’t know which parameters to select. Which chemistry parameters would be the most helpful?

Heska recommends starting with a core group of parameters, with additional parameters added if customization is necessary for the patient. The core tests can be grouped in the following organizational structure: 1) Tests for kidney health and disease (BUN, Creatinine, Phosphorus) 2) Tests for liver health and disease (ALT, ALP, Total Bilirubin) 3) Tests related to metabolic functions (Glucose, Calcium, Total Protein, Cholesterol and Albumin) 4) Specialty tests for specific situations (Amylase, Lipase) 5) Electrolytes may be performed as part of the initial diagnostic panel based on practice preference