This document was converted from the Blood Test Instructions pdf attached to this article.
Packed Cell Volume (PCV) Test is also called Hematocrit.
The test determines the percentage of red blood cells in the blood volume. Normal is 40-50% for adults and 30-40% for young puppies. A low PCV means the dog doesn’t have the normal amount of red blood cells to carry oxygen to the body efficiently (anemia), . Dogs with dangerously low PCVs may need a blood transfusion. A high PCV can indicate dehydration.
Expected Values and Danger Zones
Expected values in a health dog are:
- Glucose: >100
- Packed Cell Volume: 40-55%
- Total Protein: 5.4-7.4
- Temperature: 99.5-102.5F
Notify a doctor if values become:
- Glucose: <70 or >250
- Packed Cell Volume: <25%
- Total Protein: <3.0, >8.0
- Temperature: <98F or >104F
Packed Cell Volume Test Procedure
- Assemble what you will need for PCV, Blood Glucose and Total Protein tests. You have to run the test quickly after you have drawn the blood or it will clot, and clotted blood isn’t useful for a PCV test. You will need:
- Two hematocrit tubes
- Clay sealant tray
- 1 cc syringe with needle
- Vet wrap
- Cotton Ball
- Another Person to hold off or a tourniquet
- Blood Glucose Test
- Glucometer (Alpha-‐Trak 2)
- Glucose Test Strip—they must be the same brand as the glucometer
- Total Protein Test
- Shake your hematocrit tubes out of their container and stand them up in the grooves of the sealant tray so they are easy to access. Prep your pressure bandage (vet wrap and a cotton ball) .
- Draw a small amount of blood with a sterile syringe. Do not put heparin or anything else in the syringe. You only need about 0.2 mL.
- Remove the tourniquet if you used one and place your pressure bandage or have an assistant hold off the vein to prevent it from blowing so it will be patent for another catheter if needed.
- Inject the blood to fill 2/3rds-3/4ths of the hematocrit tubes. It is good to have two tubes, but one is fine if you can’t get enough blood. Bubbles are OK, they will be spun out.
- Press the blood-filled-end of the hematocrit tube in into the clay sealant. Do this 2-‐3 times or until there is a sealant plug 3-‐4 mm thick at one end of the hematocrit tube. Do this with both tubes.
- Place the hematocrit tubes into the centrifuge so that the two tubes are across from each other (to balance) and the clay facing outwards (if the clay is on the inside, the centripital force will push the blood out of the tubes). Close the lid.
- Run the centrifuge - spinning a hematocrit tube only takes about 1 minute.
- If necessary, run a blood glucose test while the tubes are spinning.
- The centrifuge will beep when it is done running and the lid will open. Remove one tube and press Enter to read.
- Lay the hematocrit tube in the groove on the front of the centrifuge with the sealant to the left. The tube should look something like this.
- The screen should say Enter Interface: sealant/RBC’s. Move the slider so that the black line is aligned with the boundary between the white sealant and the red blood cells at the bottom of the tube. Press Enter.
- The screen should now say RBCs/Plasma. Move the slider so that the black line is aligned with the boundary between the red blood cells and the plasma. If the boundary is at an angle, put the slider in the middle. Press Enter.
- The Screen should now say Enter Interface: Plasma/Air. Move the slider so that the black line is aligned with the boundary between the plasma and the air. Press Enter.
- The screen will show you a number as a percentage. That is the packed cell volume. Record this number. Repeat steps 11-‐15 with the second tube if you have one and average the two packed cell volumes. They should be quite similar, within about two percentage points. If they are not close, you may need to repeat the test with a new blood sample.
Total Protein Test Procedure
- Take out the refractometer and flip back the clear plastic prism cover. The refractometer is a delicate, expensive piece of equipment. Do not touch the prism with your hands or allow the tube to touch it, as this could damage the crystal.
- Break the hematocrit tube near the boundary between the red blood cells and plasma. You will be able to break a glass tube easily, plastic tubes may need to be cut with scissors or nail trimmers. Discard the side of the tube with the red blood cells.
- Hold the piece of the hematocrit tube just over the prism of the refractometer, but do not allow it to touch the crystal. Blow into the tube. You can do this without having to put your lips on the tube, just hold the tube about half an inch from your lips and blow briskly toward the opening. This should push the plasma through the tube so it drops onto the refractometer.
- Close the plastic cover over the prism. This spreads the plasma out in a thin layer over the prism.
- Look through the refractometer eye piece, with the prism in the light.
- You should see a sharp line between a blue area and a clear area. Find the scale marking that corresponds to this line. We read from the left-‐most scale, the one that goes from 0 to about 10. This is your total protein. Record this number.
- Use a Kim-‐wipe to gently wipe the plasma off the prism and prism cover and return the refractometer to its case. Do not use anything other than a clean Kim-‐wipe to do this. (The box of kim-‐wipes is green and says “Kim-‐wipes” on it. It is usually sitting next to the centrifuge. They look like small tissues but are lint-‐free and nonabrasive.) You can also clean the prism with a few drops of deionized or distilled water from the syringe stored near it, but this does not need to be done every time. Wipe the water off with a Kim-‐wipe. Do not us anything other than deionized or distilled water and a Kim-‐Wipe to clean the refractometer.
Disinfecting Test Equipment
The refractometer can be cleaned via normal methods so long as the glass components are treated with care and not corroded using harsher cleaners.
Do not spray disinfectant on the glucometer. Doing so will result in it not working. If you need to disinfect the glucometer, spray disinfectant on a paper towel and wipe the device gently.