Test for PNH (Flow Cytometry)

High-sensitivity flow cytometry^a (HSFC) is the gold standard diagnostic test for PNH^1-3

• HSFC is performed on peripheral blood—not bone marrow^1,2
• 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 transfusions^1,4

Clear reporting is essential for appropriate clinical decisions and should include^1,4:

• 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.

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

• Evaluation of RBCs alone may underreport clone size due to hemolysis and the dilution effect of transfusions^1,4
• “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 hemolysis^1,4

• 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.