Presentation on theme: "Platelet Counts Dr Kunal Sehgal, M.D. Associate Consultant"— Presentation transcript:
1 Platelet Counts Dr Kunal Sehgal, M.D. Associate Consultant PGIMER, ChandigarhTata memorial HospitalPD Hinduja HospitalPlatelet CountsDr Kunal Sehgal, M.D.Associate ConsultantHematology LaboratoryDepartment of Lab MedicinePD Hinduja National Hospital and MRC
2 Platelets – Historical Perspective 1882- Platelets recognised as distinct corpuscles – Italian pathologistGiulio BizzozeroManual Phase Contrast Microscopic Method using Neubauer chamber - ICSH - Gold StandardSemi- Automated and Fully Automated Counters1981- Hydrodynamically focused whole blood aperture IMPEDANCE counter1985- OPTICAL Platelet CountsEarly 1990s- Flow cytometric methods based on CD41/612001- Flow Cytometric RBC platelet Ratio – the new International reference Method (IRM)Briggs et al. Continuing developments with the automated platelet count. Int. Jnl. Lab. Hem.2007,29,77-91.
3 Manual Platelet Counts- The Old Gold Standard LaboriousTime IntensiveSubjectiveHigh Inter- observer CVs of %Briggs et al. Continuing developments with the automated platelet count. Int. Jnl. Lab. Hem.2007,29,77-91.
4 International Flow Reference Method The New Gold Standard RBC/Platelet Ratio MethodDual Platform MethodAbsolute Platelet Count=Platelet events X RBC countRBC events (Automated Cell Analyzer)PlateletsCD 41/61RBCISLH Task Force, Am J Clin Pathol 115, (2001)
5 Peripheral Blood Smear (Platelet count check only) Platelets to be counted in a region where RBCs and platelets are well dispersed.Atleast 10 oil immersion fields to be counted (more in lower counts)Average no. of platelets in a field multiplied by is the approximate platelet count
6 Problems of Peripheral Smear Platelet Check Platelet ClumpsPlatelet Satellitism on WBCsPoor SmearingHighly subjective
13 Automated CBC Analysers Impedance principleOptical PrincipleCounters count many more cells and hence more reproducible resultsImproved C.V. - typically less than 5%
14 Impedance Principle Coulter Principle or Resistance detection method Cells suspended in an elecrolyte solutionChange in electric impedance impedance signalImpedance signal Directly proportional to the volume of the cell
18 Optical Principle Two dimensional Light Scatter Two angles of laser ight scatter are measuredLight Scatter- 2-3°C- volume (plt size)Light Scatter- 5-15°C- refractive index (plt density)Rbc fragments have a different RI as compared to platelets and hence can be separatedOptical Fluorescence platelet countingSize vs. Fluorescence plot (Polymethine Dye)RBC fragments do not contain RNA while giant platelets and immature forms contain RNA and are called reticulated plateletsThese are easily separated from microcytic RBCs and fragments
19 Advantages of Optical Platelet Counting Jaldeep Bhansali19
22 Case Study 1 Automated CBC -Platelet count – 1.05lacs PS- many large platelet clumpsWhat do you do?Peripheral Smear – comment –Platelets are seen in many clumps. Platelets are adequate on smear (>1lac). Kindly repeat CBC for accurate platelet count if clinically indicated.
23 Case Study 2 Automated CBC -Platelet count – 2.35lacs PS- many platelet clumpsWhat do you do?Peripheral Smear – comment –Platelets are adequate on smear. Platelets are also seen in clumps.
24 Case Study 3 - 31/F,Blood Donor, East Indian Origin, Normal Hb and WBC, Impedance Plt- 134, Platelet O –162, Morphologically- Many Giant platelets
31 Based on platelet histogram findings, a peripheral smear examination was doneGiant platelets were seenPlatelet clumps seenThe sample contained adequate platelets,however we got spurious results onautomated analyzer
33 Case Study 6 Peripheral smear check- Rule out micro clots in sample 55/M A know case of Acute LeukemiaHb -7.5g% WBC x103 /ul Platelet count- 18 x103 /ulWhat do you do next?Peripheral smear check-Rule out micro clots in sampleLook for fibrin strands and platelet clumps on slideDo a peripheral smear estimation of platelet countsBe aware of the clinical decisions that depends on your result- i.e know the transfusion threshold levelsDiscuss case with clinician if required
34 Case study 7- Acceptable C.V. Case Scenario 1First run, platelet countSecond run, platelet count –A difference of Is this Acceptable? Yes- the difference is only 4%Case Scenario 2First run platelet countSecond run platelet count – 16000A difference of Is this Acceptable?NO- the difference is of 33% and will have a huge clinical impact!