If you work in veterinary practice, chances are you’ve taken a PCV more times than you can count. It’s one of those basic skills that can become almost automatic.

But because it’s so familiar, it’s also easy to rush.

A poorly filled tube, an incorrectly balanced centrifuge or a slightly dodgy reading can all affect the result. And when you’re using that number to help assess anaemia, dehydration or blood loss, getting the technique right matters.

So, if you want a refresher on how to take a manual PCV, here’s a straightforward guide from start to finish.

If you’re a veterinary nurse wanting to brush up on your PCV skills, take a look at 7 Essential Facts About Manual PCV Every Veterinary Nurse Should Know

What is a PCV?

PCV stands for packed cell volume. It tells us what proportion of a blood sample is made up of packed red blood cells.

After centrifugation, the red blood cells are forced to the bottom of the capillary tube. Above them sits the plasma, with a very thin layer of white cells and platelets between the two.

That red cell column is what we measure to obtain the PCV.

For example, if the packed red cells occupy 35% of the blood column, the PCV is 35%.

PCV is particularly useful because it’s quick, inexpensive and doesn’t require a full haematology analyser.

What equipment do you need?

To perform a manual PCV, you’ll generally need:

• EDTA blood
• Plain microhaematocrit capillary tubes
• A sealant such as sealing clay
• A microhaematocrit centrifuge
• A PCV reader or suitable measuring device
• Gloves and appropriate PPE

Some practices use different equipment, so always follow your practice’s SOP.

We also have a handy guide on placing IV’s! IV Catheter Placement in Dogs 10 Step Veterinary Nurse Guide

Step 1: Collect your blood sample

The first part of how to take a manual PCV actually happens before you even pick up a capillary tube.

Ideally, the blood sample should be collected cleanly and handled appropriately.

For a PCV, EDTA blood is commonly used because the anticoagulant prevents clotting. Make sure the sample is properly mixed by gently inverting the tube.

Don’t shake it aggressively. Excessive agitation can contribute to haemolysis and potentially affect your sample.

A sample containing a clot is also unsuitable because some red cells may become trapped within the clot, potentially affecting the result.

Step 2: Fill the capillary tube

Hold the capillary tube against the blood sample and allow it to fill.

The tube should be filled to an appropriate level, leaving a small amount of space at the end for sealing.

Try to avoid introducing air bubbles.

This sounds like a tiny detail, but bubbles can make the sample column harder to interpret and may interfere with obtaining an accurate result.

If you’re struggling to fill the tube, don’t keep fighting with it. A new tube and a fresh attempt is usually quicker than trying to interpret a poor sample.

Step 3: Seal the tube

Once the tube is filled, seal one end using your chosen sealing material.

Make sure the seal is secure.

The sealed end should be positioned appropriately in the centrifuge according to your machine’s instructions.

If the seal isn’t secure, blood can leak during centrifugation — which is both messy and a good way to ruin your sample.

Step 4: Load the centrifuge correctly

This is one of the easiest stages to rush.

When performing how to take a manual PCV, the centrifuge needs to be loaded correctly and balanced.

If you are spinning one sample, you may need to balance it with another tube containing an equivalent weight or volume, depending on your centrifuge.

Never assume that because the tube is small, balancing doesn’t matter.

An incorrectly balanced centrifuge can damage the equipment and may affect the quality of your sample separation.

Always follow the manufacturer’s instructions for centrifugation speed and time.

Step 5: Spin the sample

Once the centrifuge is loaded and balanced, run it according to your practice’s protocol and the manufacturer’s instructions.

The centrifugation process separates the blood into layers.

You’ll usually see:

Top: plasma
Middle: buffy coat
Bottom: packed red blood cells

The buffy coat contains mainly white blood cells and platelets.

Don’t be tempted to include the buffy coat when measuring the red cell column.

Step 6: Read the PCV

Once centrifugation is complete, remove the tube carefully.

This is where the PCV reader comes in.

Position the tube so that the bottom of the red cell column corresponds with the appropriate zero point and the top of the plasma corresponds with the 100% point.

The PCV is then read at the top of the packed red cell layer.

Take your time here.

If you’re getting a borderline result, it’s worth having another nurse check the reading rather than confidently recording a number that might be wrong.

Don’t forget to look at the plasma

One of the nice things about a manual PCV is that you’re not just getting one piece of information.

You can also look at the plasma.

Is it:

• Clear?
• Yellow?
• Pink?
• Red?
• Milky or turbid?

A yellow appearance may indicate increased bilirubin, while pink or red plasma may suggest haemolysis.

A milky or cloudy appearance may be associated with lipaemia.

These findings don’t give you a diagnosis by themselves, but they can provide useful additional information.

PCV and total solids

You can also use the same sample to assess total solids, depending on your equipment and practice protocol.

This is particularly useful because looking at PCV alongside total solids can provide more context than looking at either result alone.

For example, a low PCV with low total solids may suggest a different clinical picture from a low PCV with normal or increased total solids.

The results should always be interpreted alongside the patient’s history, examination findings and other diagnostics.

Common mistakes when taking a manual PCV

Even experienced veterinary nurses can occasionally make mistakes.

Some common ones include:

Using a poorly mixed sample

If the blood hasn’t been mixed properly, the cells may not be evenly distributed.

Filling the tube poorly

Air bubbles or an inadequate blood column can make the reading difficult.

Forgetting to balance the centrifuge

Always check the centrifuge before starting it.

Reading the buffy coat as part of the red cell column

The buffy coat shouldn’t normally be included when measuring the PCV.

Rushing the final reading

A PCV might take only a few minutes, but that doesn’t mean the final measurement should be a five-second job.

When might a manual PCV be particularly useful?

Manual PCVs can be useful in a variety of situations, including:

• Suspected anaemia
• Blood loss
• Monitoring patients after haemorrhage
• Dehydration
• Critically ill patients
• Blood transfusion monitoring
• When a laboratory analyser isn’t available
• Checking an unexpected analyser result

They’re particularly handy in emergency and inpatient settings because you can get a result quickly.

Final thoughts

Knowing how to take a manual PCV is one of those fundamental veterinary nursing skills that’s worth keeping sharp.

The actual process is simple, but small errors can have surprisingly big consequences.

Take the time to collect a good sample, fill and seal the tube properly, balance the centrifuge and read the result carefully. And don’t forget that the sample can tell you more than just the PCV — the plasma appearance and total solids can also add useful information.

Most importantly, don’t interpret the number in isolation.

A PCV is one piece of the clinical puzzle, not the whole picture.