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Test for PNH (Flow Cytometry)


High-sensitivity flow cytometrya (HSFC) is the gold standard diagnostic test for PNH1-3

  • HSFC is performed on peripheral blood—not bone marrow1,2
  • Labs should perform PNH HSFC on white blood cells (WBCs) (using >1 reagent) and on red blood cells (RBCs)1,4
    • Granulocytes using FLAER/CD24 combinations give most accurate estimate of PNH clone size2
    • Evaluation of RBCs alone may not be accurate due to hemolysis and the dilution effect of transfusions1,4

Clear reporting is essential for appropriate clinical decisions and should include1,4:

  • Clone size for each cell lineage (ie, granulocytes, monocytes, and RBCs)
  • Proportion of Type II and III (percentage of GPI-deficient cells) as well as total RBCs
  • Sensitivity level used (0.01% high-sensitivity analysis is ideal)
  • All previous flow results in order to monitor clonal expansion
  • The International PNH Interest Group (IPIG) recommends routine monitoring every 6 to 12 months of patients who have an identified clone5

aDetects PNH cells down to a 0.01% clone size.


PNH symptom incidence rate

Labs should perform PNH HSFC on RBCs, and on WBCs using >1 reagent1,4

  • Evaluation of RBCs alone may underreport clone size due to hemolysis and the dilution effect of transfusions1,4
  • “Routine” CD55- and/or CD59-based approaches are neither accurate nor sensitive below the 1%-4% clone size2
  • Granulocytes give most accurate estimate of PNH clone size2
    • FLAER/CD24 combinations recommended to detect PNH granulocytes2
  • Low RBC clone size compared to WBC clone size indicative of intravascular hemolysis1,4
  • The International PNH Interest Group (IPIG) recommends that high-sensitivity flow cytometry for PNH be performed5:
    • After establishment of a PNH diagnosis:
      • Every 6-12 months
    • In patients with AA or MDS:
      • At diagnosis and yearly, regardless of clone identification

For more information about performing a full clinical assessment to diagnose PNH, Download the Clinical Diagnostic Cheat Sheet.

References: 1. Borowitz MJ, et al. Cytometry B Clin Cytom. 2010;78(4):211-230. 2. Sutherland DR, et al. Cytometry B Clin Cytom. 2018;94(1):23-48. 3. Sharma VR. Clin Adv Hematol Oncol. 2013;11 Suppl 13(9):2-8. 4. Illingworth A, et al. Cytometry B Clin Cytom. 2018;94(1):49-66. 5. Parker C, et al. Blood. 2005;106(12):3699-3709.

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