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What tube is manual platelet count in?

When collecting blood samples for a manual platelet count, it is important to use the correct tube type. The tube type can significantly impact the accuracy of the platelet count result. This article will discuss the tube that should be used for manual platelet counts, why it is important, and provide a step-by-step overview of the manual platelet count procedure.

Using EDTA Tubes for Manual Platelet Counts

Ethylenediaminetetraacetic acid (EDTA) tubes are the recommended tube type for manual platelet counts. EDTA tubes contain the anticoagulant EDTA which binds calcium and prevents blood from clotting. This allows for an accurate platelet count since platelets are best measured in non-clotted blood.

Other common tube types like heparin or citrate tubes are not ideal for platelet counts. Heparin binds platelets which can lead to platelet clumping and inaccurate results. Citrate is a calcium chelator which can cause morphologic changes to platelets affecting the count. Therefore, EDTA tubes are the gold standard.

Why EDTA Tubes?

There are a few key reasons why EDTA tubes are ideal for manual platelet counts:

  • Prevents clotting – Platelets are fragile and best measured in non-clotted blood. EDTA binds calcium to prevent coagulation.
  • Minimal platelet binding – Unlike heparin, EDTA does not bind and clump platelets which could lower the count.
  • Maintains platelet integrity – Platelet structure is not altered compared to other anticoagulants.
  • Stabilizes blood – EDTA keeps the blood sample stable for up to 48 hours allowing time for testing.

Overall, EDTA is considered the gold standard tube for platelet counts due to its ability to prevent clotting without altering platelet structure or numbers. This allows for the most accurate representation of the patient’s true platelet levels.

Manual Platelet Count Procedure

Here is an overview of the step-by-step procedure for performing a manual platelet count using EDTA tubes:

  1. Collect blood sample – Use EDTA tube and proper phlebotomy technique to collect blood sample for platelet count.
  2. Make dilutions – Make 1:20 and 1:100 dilutions of blood sample in ammonium oxalate solution. Ammonium oxalate also prevents clotting.
  3. Load chambers – Load chambers of hemocytometer with dilutions. Let stand for 2-3 minutes to allow cells to settle.
  4. Count platelets – Under light microscope, count all platelets in 1mm center square and 1mm corner squares. Count each dilution twice.
  5. Calculate – Average the duplicate counts and calculate the platelet count per cubic mm using the following equation:

    Platelet count = Average count x Dilution x Depth (0.1mm) x Area (mm2) / # squares counted

  6. Verify result – Confirm result is within normal reference range. Repeat procedure if result is abnormal before reporting.

Performing the proper dilutions and using the hemocytometer chamber helps standardize the platelet count for accurate results. Duplicate counts improve precision. Careful technique is vital for reliable manual platelet counts.

Reference Ranges

The normal reference range for platelet counts is:

  • Adult: 150,000-450,000 platelets/mm3
  • Child: 150,000-400,000 platelets/mm3

Higher or lower counts may indicate underlying conditions. For example:

Platelet Count Condition
Low <150,000/mm3 Thrombocytopenia
High >450,000/mm3 Thrombocytosis

Causes of Abnormal Platelet Counts

There are many potential causes leading to abnormally low or high platelet counts. These include:

Thrombocytopenia Causes

  • Viral infections like mononucleosis, measles, HIV
  • Immune thrombocytopenic purpura (ITP)
  • Cancer like leukemia, lymphoma
  • Chemotherapy and radiation treatment
  • Enlarged spleen sequestering platelets
  • Pregnancy
  • Autoimmune disorders like lupus
  • Drugs like heparin, quinine, sulfonamides
  • Disseminated intravascular coagulation (DIC)
  • Liver disease

Thrombocytosis Causes

  • Iron deficiency anemia
  • Inflammatory disease like rheumatoid arthritis
  • Tissue damage like burns, surgery
  • Hyposplenism or asplenia
  • Hemolytic anemia
  • Chronic myeloproliferative disorder
  • Cancer like lung, colon, ovarian

Summary

In summary, key points about the tube for manual platelet counts include:

  • Use EDTA tubes – prevents clotting and maintains platelet integrity
  • Avoid heparin or citrate tubes – can alter platelet appearance and counts
  • Follow meticulous technique for dilutions, mixing, and counting
  • Duplicate counts and calculations improve precision
  • Reference range is 150,000-450,000 platelets/mm3
  • High or low counts can signify underlying disorders

Performing platelet counts properly in EDTA tubes allows clinicians to accurately assess patients’ platelet levels and detect potential bleeding or clotting conditions. Manual platelet counts require careful attention to detail but provide valuable information compared to automated methods alone. When performed correctly, the manual platelet count remains an important diagnostic tool.