This is a tube of 110 mm long and with an internal bore diameter of 3mm
The tube is closed at one end.
This tube is graduated on both sides from 0-10 in ascending and descending order
The tube holds approximately 1 ml of blood
What are the uses of Wintrobe tube
The uses are
1.Determination of Packed cell volume (PCV)
2.Determination of Erythrocyte sedimentation rate (ESR)
3.Preparation of Buffy coat smear. This smear is used to determine LE cell phenomenon and to study the abnormal cells in cases of aleukemic leukemia.
What is Packed cell volume (PCV)
Packed cell volume is defined as ratio of volume of packed RBCs to that of whole blood which is the volume occupied by red blood cells when anticoagulated blood is centrifuged.
This is expressed in percentage.
How do you estimate PCV by wintrobe method
a.Fill the pasteur pipette with properly mixed anticoagulated blood .
b.Introduce the pipette at the bottom of the wintrobe tube and slowly fill it upto 10 mark.
c.Make sure that the tip of pipette should remain below the rising meniscus of blood to avoid foaming.
d. Centrifuge the tube at 3000 rpm for 30 min.
After centrifugation, Three layers are seen ( See image below)
Upper most layer is PLASMA
Middle narrow layer is BUFFY COAT . This is comprised of WBCs and platelets
Lower most layer is the PACKED RBCs
Note the lower most height of column of packed RBC layer this has to be expressed in percentage.
What are the normal values of PCV
NORMAL VALUES are as follows
Adult male – 40 – 50%
Adult female – 38 – 45%
New born – 44 – 60%
Why is the PCV test asked by the clinician
It is commonly asked as a part of evaluation of anemias. Apart for this, the other reasons are to monitor the treatment of anemias, polycythemia and any dehydration
What are the causes of increased PCV
The causes of Increased PCV are
The most common cause of increased PCV is dehydration
Other causes include
Polycythemia: Primary or secondary
Some causes of secondary polycythemia
Lung or heart diseases: there will be increased production of RBC’s to meet the oxygen demands
Smoking and alcohol consumption
Paraneoplastic syndromes where there is increase in erythropoietin levels: Eg Hepatocellular carcinoma, Renal cell carcinoma, Adrenal tumors etc
What are the causes of decreased PCV
Anemias and leukemias
Secondary to bleeding
A small drop may be seen in pregnancy
Renal diseases may result in decrease in production of erythropoietin.