Platelet countPlatelet count

ObjectivesObjectives To understand the importance of doing a To understand the importance of doing a

platelet countplatelet count To know the methods of performing a To know the methods of performing a

platelet count .platelet count . To perform a platelet count .To perform a platelet count . Know the possible sources of error and Know the possible sources of error and

precautions to be taken in conducting a precautions to be taken in conducting a platelet count.platelet count.

Know the normal values.Know the normal values. Know the possible causes of abnormal Know the possible causes of abnormal

platelet counts.platelet counts.

What is a platelet What is a platelet count?count?

Why is it done?Why is it done?

Bleeding-petechiaeBleeding-petechiae

Functions of platelets

Why is platelet counting Why is platelet counting difficult?difficult?

They are small and difficult to discern.They are small and difficult to discern. Their adhesive character-attach readily to Their adhesive character-attach readily to

glassware, particles or debris in the diluting glassware, particles or debris in the diluting fluid.fluid.

They clump easily.They clump easily. Not evenly distributed in the mixture of Not evenly distributed in the mixture of

blood and diluting fluid.blood and diluting fluid. They readily disintegrate in the blood They readily disintegrate in the blood

diluted with fluid making it difficult to diluted with fluid making it difficult to distinguish them from debris.distinguish them from debris.

Therefore unless carefully done ,accurate Therefore unless carefully done ,accurate counting of platelets becomes impossible.counting of platelets becomes impossible.

Methods Methods

Haemocytometry (direct count)Haemocytometry (direct count)

1.Brecher-Cronkite method1.Brecher-Cronkite method

2.Rees –Ecker method 2.Rees –Ecker method Study of blood smear (indirect Study of blood smear (indirect

method)method) Automated counting.Automated counting.

Brecher –Cronkite methodBrecher –Cronkite methodPrinciple:Principle:The diluent contains Ammonium Oxalate.The diluent contains Ammonium Oxalate.This completely lyses the red cells.This completely lyses the red cells.the platelets are then counted with a the platelets are then counted with a

phase –haemocytometer and phase phase –haemocytometer and phase contrast microscope to enhance the contrast microscope to enhance the refractileness of the platelets.(or refractileness of the platelets.(or ordinary microscope)ordinary microscope)

Advantage:Advantage: Identification is easier.Identification is easier. The error involved is lowThe error involved is low

TechniqueTechnique

Platelets as seen on Platelets as seen on blood smearsblood smears

Calculation Calculation

Sources of errorSources of error

Precautions to be takenPrecautions to be taken Glassware must be scrupulously cleaned .Glassware must be scrupulously cleaned .

debris and dust are the main sources of error debris and dust are the main sources of error as they are easily mistaken for platelets.as they are easily mistaken for platelets.

The diluting fluid must be filtered just before The diluting fluid must be filtered just before use .use .to remove particles.to remove particles.

If venous blood is used the platelets must be If venous blood is used the platelets must be counted within 3 hours.counted within 3 hours.delay causes disintegration and clumping of delay causes disintegration and clumping of platelets.platelets.

Blood should be rapidly diluted .Blood should be rapidly diluted .this is essential to prevent clumping.this is essential to prevent clumping.

Precautions to be takenPrecautions to be taken Blood must be thoroughly mixed with the Blood must be thoroughly mixed with the

diluent by shaking the contents at least for 10 diluent by shaking the contents at least for 10 minutes.minutes.inadequate mixing results in clumping of inadequate mixing results in clumping of platelets.platelets.

The charged chamber should be kept for 15 The charged chamber should be kept for 15 minutes under petri dish.minutes under petri dish.to prevent evaporation and for the cells to to prevent evaporation and for the cells to settle down.settle down.

If other haematologic tests are to be done If other haematologic tests are to be done with platelet count ,and blood is used from with platelet count ,and blood is used from the same puncture ,take blood for the platelet the same puncture ,take blood for the platelet count first.count first.

The finger should not be squeezed The finger should not be squeezed excessively to collect blood .excessively to collect blood .

Conditions affecting number of Conditions affecting number of platelets in bloodplatelets in blood

ThrombocytopeniaThrombocytopenia

low platelet countlow platelet count ThrombocytosisThrombocytosis

high platelet counthigh platelet count

Thrombocytopenia Thrombocytopenia (low platelet count)(low platelet count)

CausesCauses Reduced production of plateletsReduced production of platelets Increased breakdown of plateletsIncreased breakdown of platelets Trapping of platelets in the Trapping of platelets in the

spleenspleen

Thrombocytopenia (low platelet Thrombocytopenia (low platelet count)count)

As a result ofAs a result of a bone marrow disorder such as a bone marrow disorder such as

leukemia leukemia an immune system malfunction an immune system malfunction as a reaction to a medication. as a reaction to a medication.

Complications may range from none at Complications may range from none at all to severe bleeding. all to severe bleeding.

The greatest risk is when platelet The greatest risk is when platelet count falls very low <10,000 per count falls very low <10,000 per microliter . internal bleeding may microliter . internal bleeding may occur despite a lack of any injury.occur despite a lack of any injury.

Reduced production of Reduced production of plateletsplatelets

leukemia leukemia some types of anemia, some types of anemia, Viral infections, Viral infections, cancers that affect bone marrow, cancers that affect bone marrow, chemotherapy drugs chemotherapy drugs heavy alcohol consumptionheavy alcohol consumption

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Increased breakdown of Increased breakdown of plateletsplatelets

PregnancyPregnancy Idiopathic thrombocytopenic purpuraIdiopathic thrombocytopenic purpura

(ITP), (ITP), Other autoimmune diseasesOther autoimmune diseases,, such as such as

lupus and rheumatoid arthritis, lupus and rheumatoid arthritis, SepticemiaSepticemia severe bacterial severe bacterial infectionsinfections, , Thrombotic thrombocytopenic Thrombotic thrombocytopenic

purpurapurpura (TTP), (TTP), a rare, life-threatening a rare, life-threatening condition TTP can happen sporadically or condition TTP can happen sporadically or as a side effect of some medications. as a side effect of some medications.

Hemolytic uremic syndromeHemolytic uremic syndrome, , Dengue feverDengue fever

Trapping of platelets in the Trapping of platelets in the spleenspleen

may harbor too many platelets, may harbor too many platelets, causing a decrease in the number of causing a decrease in the number of platelets in circulation. platelets in circulation.

Signs and symptoms of a low blood Signs and symptoms of a low blood platelet count may include:platelet count may include:

Easy or excessive Easy or excessive bruisingbruising Superficial bleeding into Superficial bleeding into

the skin that appears as a the skin that appears as a rash of pinpoint-sized rash of pinpoint-sized reddish-purple spots reddish-purple spots ((petechiae),petechiae), usually on the usually on the lower legs lower legs

Prolonged bleedingProlonged bleeding from from cuts cuts

Spontaneous bleedingSpontaneous bleeding from gums or nose from gums or nose

Blood Blood in urine or stools in urine or stools Unusually heavy menstrual Unusually heavy menstrual

flows flows Profuse bleedingProfuse bleeding during during

surgery surgery Serious or widespread Serious or widespread

bleedingbleeding indicates an indicates an emergency and requires emergency and requires immediate care.immediate care.

ThrombocytosisThrombocytosis(high platelet levels ) (high platelet levels )

reaction to an infectionreaction to an infection surgerysurgery certain medicationscertain medications Polycythemia vera, in which the Polycythemia vera, in which the

bone marrow produces too many bone marrow produces too many platelets too quickly. platelets too quickly.

Questions Questions Why does the platelet count give inaccurate Why does the platelet count give inaccurate

results unless performed carefully?results unless performed carefully? What are the different methods of platelet What are the different methods of platelet

count?count? What is the principle of the Brecher –Cronkite What is the principle of the Brecher –Cronkite

method?method? Why is the reagent filtered before every use?Why is the reagent filtered before every use? Why is venous blood preferred to capillary Why is venous blood preferred to capillary

blood for platelet count?blood for platelet count? Why is glassware cleaned thoroughly for Why is glassware cleaned thoroughly for

platelet count?platelet count?

Questions Questions Why is the blood rapidly diluted and thoroughly Why is the blood rapidly diluted and thoroughly

mixed with the diluting fluid?mixed with the diluting fluid? Why is the charged chamber covered by a Why is the charged chamber covered by a

petridish for 15 minutes?petridish for 15 minutes? How do you identify platelets under the high How do you identify platelets under the high

power objective?power objective? What are the sources of error in manual method What are the sources of error in manual method

of platelet count?of platelet count? What is the normal platelet count?What is the normal platelet count? What are the properties of platelets?what are What are the properties of platelets?what are

their functions?their functions? What are the causes of thrombocytosis and What are the causes of thrombocytosis and

thrombocytopenia?thrombocytopenia?

Happy counting!Happy counting!