we use EDTA as a anti coagulant for collection of blood,so may be it is due to the expiry and composition error of anticougulant in collecting tube material.

There are many reasons cause this phenomenon but it can due to the EDTA or anticoagulant that you use.Also, in some cases because of some drugs such as antibiotics(aggregation of platelet) you may observe giant platelet,In addition you had better check you staining process.or it may because of the collecting sample.

.you had better check PBS when you prepare the smear to test .good luck

EDTA may cause clumping of platelets which may make them appear larger than normal. Activation of platelets during phlebotomy may give a similar result. Lastly, how do you define 'normal healthy population'?

there are many populations who have large platelets and there is a normal distribution within the "healthy" population. A recent study from Italy and one from the UK both reported that there is significant variability in this (as well as platelet count) in their healthy populations. Additionally, there are inherited platelet disorders that result in macrothrombocytes -- usually with a lowish platelet count (100-150). Finally, a few large platelets may be normal for anyone -- it depends on how frequent they are.

In samples with EDTA, what you see is not big platelets but platelet clumping. Real Big plateles (besides normal deviation) can be seen in platelet functional disorders such as Bernard- Soulier, quantitative disorders such as ITP, and clonal diseases such as Chronic myeloproliferative Disorders and MDS.

Large platelets are like reticulocytes, early release from the bone marrow when needed, such as in bleeding or platelet sequestration- also of course in myeloproliferative disorders.

After the release of Platelets from bone marrow . Not only Platelets all the cells will traverse Spleen for Pitting. That's how Bioconcave shape of Rbc's. Some of the cells they dont enter the BM & Escape . Such Platelets which Escaped from spleenic processing will Look Little larger then normal Platelets

If you look at your CBC (complete blood count) results, there is an item called MPV or mean platelet volume since the CBC is counted through a coulter counting machine using cells passing through a pore measured according to which cells are being counted, it also measures the cell volume and reports the mean.

Therefore, when the MPV increases as in presence of bleeding, we consider that an expression of younger platelets being released from the bone marrow, very much like reticulocytes for RBC which are larger in volume compared to older cells. in the absence of release of young platelets, there are abnormal conditions that is associated with abnormally larege platelets such as Glanzman thrombasthenia or in myeloproliferative disorders such as P Vera, essential thromocythemia, or primary myelofibrosis.

Need to exclude technical preparation causes as others have alluded to. Which 'normal population " is it ? Other haematological parameters available? May need to consider the macrothrombocytopenia disorders such as May-Hegglin anomaly, Sebastian etc . Any Dohle bodies in the leucocytes? Harris syndrome in East Bengal populations.

Platelets size is evaluated by mean platelet volume (MPV) in modern Blood counters. The MPV in the general polulation is arround 9-10 fl. If you observe the area under the curve you MAY see a dispersion. This is due to the presence of normal juvenile large platelets [>11fl]. The more juvenile the more larger platelets are. That's the explanation in the normal population. In patients with inmune Thrombocytopenia and some hereditary thrombocytopenias this is more evident because the bone marrow is producing more megacariocytes (platelets precursors) to compense destruction by the spleen.

One thing is platelets clumps and another is large platelets. Platelet clumps, as has being previously said, are due to spontaneous agglutination or EDTA induced (it is believed that people can have antibodies against EDTA in blood and this could be the reason for pseudothrombocytopenia seen with the blood counters). In the case of large platelets in the normal population I agree with Dr. Emanuel Besa. Large platelets are juvenile platelets that appear spontaneously when blood is drawn. If you can see the dispersion of the MPV you would see that there is a proportion of platelets bigger than 11 fl (the normal MPV fluctuates between 9-10 fl). When you see a normal count (150.000-400.000/ul) with platelets bigger than 11 fl one should assume consumption or blood loss. In the first case you can have a normal number of platelets (compensated immune thrombocytopenia) or low platelets (tipical immune thrombocytopenia). In the case of blood loss usually platelets are increased to the limit of normal or even more than 400.000/ul. This is a consequence of TPO increase and hyperproduction by the bone marrow of megakariocytes which liberates juvenile platelets. As has been previously said there are a multiple of hereditary thrombocytopenias with macrothrombocytes but these are thrombocytopenias due to ineffective production, in general, and not consumption. Hope I have been explicit.

It can be normal, if the percentage of the giant platelet is not high.

Macrothrombocytopenia, as it is formally known, occurs when the normally small and highly fragmented platelets are bigger than usual. Many people who have large platelets also have a reduced platelet count. The platelet size can be genetic, as seen in people with Bernard-Soulier syndrome, gray platelet syndrome, and May-Hegglin anomaly. In other cases, it may occur in response to problems in the bone marrow, such as cancers that disrupt the production of blood cells.

The most common problem experienced by people with large platelets is increased bleeding. The oversized platelets cannot clot properly and as a result, the patient may bleed freely from even small injuries, develop substantial bruising, and experience internal bleeding that is difficult to stop because the blood does not clot. This can become very dangerous if the bleeding is excessive and when it occurs internally, the patient may not be aware of it until substantial blood loss has occurred.

Dear Afsheen,

I appreciate your genuine doubt about the mysterious behaviour of human Platelets and the differing morphological appearances even in a normal healthy person. Our colleagues have already explained the different angles of the problem of morphological variations ranging from Platelet dysfunctional disorders like Glanzman's and BSS to the Myeloproliferative Neoplasms, and the MPV to assess the Platelet volume from the electronic blood counters. However your observation of these morphological variations in absolutely healthy individuals needs some more explanations on the kinetics of Platelet production from the largest Mother Cell viz Megakaryocyte. Giulio Bizzozero(1862) is supposed to be the Father of Platelets who first described these novel morphological elements in blood smears but still 150 years later we don't fully know the entire kinetics of platelet production from Megakaryocytes. Junt et al(2007) used live imaging with multiphoton Intravital Microscopy to visualise platelet production in vivo and came up with dramatic conclusions about the PROPLATELETs(long branching segments of Mega Ks) pushing through the endothelial lining of Bone Marrow sinusoids which look like beads on a chain and the fission giving rise to larger chunks of material. The release of normal sized platelets from these chunks depends on further work by Microtubules in these elements transferring the alpha and dense granules over to the forming platelet body. The Shear force of moving blood helps fissioning these particles and the released larger chunks go and get stuck in capillary beds. As our Lungs have the maximum area filled with capillaries it is supposed that the dynamics of inflation and deflation of our lungs churns these large Proplatelets into yet another intermediate product called PREPLATELETs before becoming the near 10 ul normal platelets seen in circulation. PROPLATELET counts were raised in Prepulmonary vessels compared to Post pulmonary vessels where as Platelet counts showed the reverse values. Invertibrates don't have separate Platelets but have cells called Haemocytes in their Haemolymph where as in Vertibrates these diverge into two major populations the Platelets and Leucocytes. However we now know that our Platelets do have major immune functions and the magnitude is enormous taking into consideration their huge numbers(100 Billion new Platelets daily each platelet having only 8 to 10 day life span). In fact Platelets are responsible for killing intraerythrocytic Malaria Parasites by coming around parasitized RBCs and generating various cytokines and chemokines. The drop in Platelet count observed in Malaria may be partly because of this fact which was previously explained as Splenic sensitivity. They act as Sponges to carry hormones and other substances from one place to another, carry the necessary clotting agets like a bomber jet to localise the coagulation where it is needed rather than inducing a general hypercoagulability. They have Toll Like Receptors(TLRs) which have innate immune functions. Platelets help malignant metastasis as seen in Ovarian malignancies( bad prognosis in such patients with high platelet counts).

If you are interested you may refer to a review article ' Platelets and Immune Continuum' by John Semple et al in Nature Review Immunology April 2011, in which the JCB article on ' Cytoskeletal mechanics of Proplatelet maturation and platelet release' by Thon JN et al 2010(J Cell Biology 2010, 191. 861-74) is cited.

You may know that the treatment of Splenectomy(removal of Spleen) was suggested by a Medical Student in 1916 to his Professor for a patient with ITP before we knew anything about Immunology, the self experimentation by Dr. Harrison by receiving 500 ml of blood from such a patient in 1952 and ending up in ICU with severe thrombocytopenia and convulsons(our knowledge of Antiplatelet Antibody came up at that stage), leave alone the complex Platelet immunology. Personally I am dead against this form of treatment for Immune Thrombocytopenic Purpura and the article on Vascular complications of Splenectomy for ITP which appeared in Blood journal(Blood 2009: 117: 2861-68) supports my earlier negative view on Splenectomy as a form of Rx for ITP even though the guidelines still speaks of this mode of Rx in ITP). I am sorry if I have gone too far in Platelet Physiology; but I have a keen interest in this topic.

Professor Kasim Salim.

When bone marrow is producing more and younger Platelets, the platelets may be larger.

Very True Pankaj. However the bodies we see as large platelets in normal persons may be PREPLATELETS which are of inermediate size and the PROPLATELETS are the ones discharged from Mega Ks into Bone Marrow sinusoids like pseudopodia. However interconversion of PREPLATELET back to larger PROPLATELET and vice versa can happen in circulation by Microtubule mechanisms. This phenomenon accounts for the varying sizes of Platelets in health.

I highly appreciated all of you people who answer me,give their time and increased my knowledge.but in my case problem is that we reported about 1300 samples daily and abrutly arround 500-600 patients show large platelets with high MPV and performing manual platelets count of all these patients is a tedious job.so,i want to find out the sourses of error which cause this problem other than clinical condition.

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Dear Colleague,

I agree with all precedent comments; and you have to indicate to us which size did you observed , defined as "large platelet". Is this size include in the SD of the MPV defined above or not ? if no t,is the platelet curve normal and other blood compounds not counted as platelets ? With which machine do you appreciate your platelet volume or only on microscopy ? All factors that could be involved in a "normal" biological variation of platelet volume in different human populations.

Best regards

Didier JAMBOU

Ps in general macrothombocytes, as found in May-Haegglin disease are rather much more bigger than "normal" platelet, even with variations in size ( equivalent to red olood cell size).

early B12/folic acid def. may be one of D possibility. Look 4 hypersegmented polys in same smear

Let's all be aware of two items. First, there should be clarity in the definition of large platelet and giant platelet (I consider them two different things with different clinical etiology and indications). What is your definition? Second, the measurement of MPV will differ depending on the instrument it is measured on, the anticoagulant used, the age of the sample, storage temperatures, among other things. There is a current working group underway with the ICSH to understand and attempt standardization of MPV. Standardization is mandatory in order to promote clinical utility about platelet size as measured by various instruments available to laboratories.

Dear colleagues

once again i appreciated your response.we use Beckman Coulter LH-750.and MPV is more than 10,platelate curve is normal but platelets count is lower by instrument but when we observe morphology under microscope there is many large platelets in sufficient number which shows that count of platelets is normal but because of unknown reason it counted low by instrument and we verify it by manual platelet counting technique,the count become normal.this occour even in fresh collected sample which is proceses within 2-6 hours.

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Dear Afsheen,

When we find this disparity between machine count and manual count we usually explain this phenomenon as a machine misinterpretation of the Platelet count as the large Platelet bodies may be passing through the white cell port and get counted as white cells instead. Similarly if there are many Red Cell fragments in the blood they could very well be counted as Platelets even giving a higher value for Platelet numbers than what is real. I have already mentioned an incident in which extracellular Anaplasma were counted as Platelets by the machine and transiently corrected the thrombocytopenia in a patient who presented with 4 weeks of rigor and fever with initial Thrombocytopenia and Neutropenia.

If the Platelet sizes are so heterogeneous one should always look for some reasons for the abnormal sizes. Our present day knowledge about such conditions with Megathrombocytes is limited and only further research can unveil some of those strange condtions. However one should be knowledgeable about the Platelet normal Platelet production from Megaks and its dynamics, with large Proplatelets and the intermediate sized Preplatelets which can go back and forth in the circulationg blood due to their microtubule activity, before interpreting these findings as non-physiological and stamping them as signs of disease. I have even seen ITP diagnosed in one such healthy person with Megathrombocytes from machine counts, ending up in the unwelcome procedure of Splenectomy. This person's Post Splenectomy Blood Film created a lot of confusion and discussions. So always make sure that the film is examined properly and patient's clinical state taken into consideration when we come across Thrombocytopenia recorded by electronic cell counters.

Dear colleagues

I want to use your value able answers,for starting my reseach so plz send the reffrences of your answers.

Some people have an inherited large platelets, but more importantly you must also check the platelet count and platelet mass as this may be the beginning of immune thrombocytopaenic purpura (ITP).

There is an frequent entity called "familiar pseudo macro thrombocitopenia"

Those patients show slightly thrombocitopenia (or midly) but with higher volume (VPM). The analyzers are unable to count those platetes correctly, and some times count the greatest one as lymphocites, and usually give us some kind of alarms.

Of course, it is benign, because there is no bleeding signs or symptoms, neither has greater risk of bleeding after delivery or surgery.

I sympathize with you Afsheen. Cell counter induced thrombocytopenia bugs us as well and we have found invariably the manual counts to be higher than the machine reads and there are always large platelets underlying the erroneous reads. However we need to manual counts all the time as there is a big difference in approaches to the management.

Is there any relationship of giant platelets with the type of anticoagulant used?

There is a relationship between swelling of PLT and time in EDTA. Platelets, just like red cells, will swell over time in any form of EDTA.

In Healthy poppulation Mega Thromboctyes Can Be Seen . If We consider the nocturanal cycle of Bone Marow relase. Morning Counts are low . Afternoon Counts

Raises then in Night when we go to bed Rhythemic sleep Counts become at basal

Leval. In this process wheather counts are done in Beckmens couter or Nihan Khoden Japan. only parameater to look in this disscuastion MPV & PDW.Accordingly

Nocturnal Realase.. I agree Partially with Dr.Sanjay Deshmukh to look for B 12

Deficency.

Yes, please be aware the response of the MPV differs on impedance systems vs. a system using scatter such as Siemens.

I agree with Dr. Lambert

Afsheen Ali I advise you to first run a pilot project, in which you can follow those people who are otherwise normal but have megathrombocytes: you may pick up initial phases of primary immune thrombocytopenia, infections, megaloblastic anaemia, etc. If a completely normal person has megathrombocytes on multiple occasions in your population, there exists a reason to research over it.

Different populations may have few large platelets which could be normal. However, abnormally large platelets may be seen in Glanzman thrombasthenia, primary myelofibrosis or in myeloproliferative disorders. Occasional large platelets in normal healthy populations should not be a cause of worry.

I am agree with Omer.

Most of my "patients", studied because they have a slight decrease platelets level and large medium platelet volume, are sane!

GP must be educated to avoid unnecessary alarms and patients concern!

This is interesting finding Afsheen. Giant platelets can be seen in random normal patients, is a well known fact. But they are also common in certain ethnic groups, e,g, north eastern subcontinent. I am not aware of such finding in north western parts of subcontinent. You can compare MPV of these individuals on subsequent follow up and also look for which ethnic group they belong to. You can also contact other laboratories in your area for similar finding. But before this exercise, make sure that you have ruled out other causes like EDTA use (try citrate) or megaloblastic anemia.

WHAT COULD BE INDICATIONS OF BONE MARROW in patients with giant cell associated thrombocytopenia

could presence of giant cells signify

ITP

HAEMATOLOGICAL MALIGNANCY

PSEUDOTHROMBOCYTOPENIA

A patient with no previous history presents with anaemia, tear drop poikilocytes and large platelets. What is the differential diagnosis? What tests should be performed as follow up to confirm the diagnosis?