Platelet count

Platelet count is a crucial parameter in assessing the coagulation status and overall health of an individual. It measures the number of platelets present in a specified volume of blood and helps in diagnosing various disorders, such as thrombocytopenia or thrombocytosis. One of the commonly used methods to determine platelet count is the Neubauer chamber method, which utilizes a specialized counting chamber and a microscope.

Requirements:

To perform platelet count using the Neubauer chamber method, the following materials are required:

  • Neubauer counting chamber: A specially designed slide with a grid pattern and a known depth to enable accurate counting.
  • Microscope: A compound microscope with appropriate magnification (typically 10x or 40x objective) to visualize platelets.
  • Hemocytometer cover slip: A cover slip that is placed over the counting chamber to create a defined volume for counting.
  • Phosphate-buffered saline (PBS): A solution used to dilute the blood sample for better visualization and counting.
  • Lancet or needle: To obtain a small blood sample for analysis.
  • Pipettes: To measure and transfer the blood and PBS accurately.

Principle:

The Neubauer chamber is divided into a series of grids, which are further subdivided into smaller squares. Each large square represents a known volume, typically 0.1 μL, and contains a specific number of smaller squares. By counting the platelets in a specific number of squares and extrapolating the count to the entire chamber, the platelet count can be calculated.

Procedure:

  1. Clean the Neubauer counting chamber and cover slip thoroughly and dry them.
  2. Obtain a small blood sample by pricking the patient's finger with a lancet or needle.
  3. Mix the blood sample gently with an appropriate diluent, such as PBS, to avoid clotting.
  4. Place the counting chamber on the microscope stage and secure it.
  5. Load the diluted blood into the counting chamber using a pipette, ensuring it fills the chamber evenly.
  6. Place the cover slip on top of the counting chamber, allowing it to settle by capillary action.
  7. Allow the platelets to settle for a few minutes to ensure an even distribution.
  8. Adjust the microscope to the appropriate magnification and focus on the central grid of the counting chamber.
  9. Count the platelets in a specific number of squares, usually within the central grid.
  10. Repeat the counting process in multiple squares to obtain an accurate average count.
  11. Calculate the platelet count using the formula provided by the manufacturer or a standard formula based on the chamber's specifications.

Results and Normal Values:

The result of the platelet count using the Neubauer chamber method is expressed as the number of platelets per microliter (μL) of blood. The normal platelet count range for adults is typically between 150,000 and 450,000 platelets/μL.

Quality Control (QC):

To ensure the accuracy and precision of platelet counts obtained using the Neubauer chamber method, it is essential to perform regular quality control measures. This involves running control samples with known platelet concentrations to verify the accuracy of the counting procedure. The control samples should be within an acceptable range defined by the laboratory's protocols.

Interpretation:

Interpretation of platelet count results obtained using the Neubauer chamber method depends on the specific clinical context. Abnormally low platelet counts (thrombocytopenia) may indicate conditions such as immune thrombocytopenic purpura, bone marrow disorders, or certain infections. Conversely, elevated platelet counts (thrombocytosis) may be associated with conditions like essential thrombocythemia, iron deficiency anemia, or inflammatory diseases. It is important to consider these results in conjunction with the patient's medical history, symptoms, and other relevant laboratory findings for an accurate diagnosis and appropriate management.

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