Diagnosis of PNH

PNH is diagnosed through flow cytometry testing, using fluorescently labelled inactive variant of protein aerolysin (FLAER) to identify GPI-deficient cells. Importantly, RBC analysis alone may underestimate the PNH clone size, therefore the analysis of polymorphonuclear cells is also necessary.1,2

paroxysmal nocturnal haemoglobinuria pathophysiology- PNH diagnosis, normal peripheral blood sample, PNH sample

Laboratory abnormalities include direct antiglobulin test (DAT)-negative haemolytic anaemia, reticulocytosis and elevated LDH levels. Haemoglobin and haematocrit can be near normal in patients with adequate reticulocyte production. Iron deficiency can be present in some patients due to chronic haemoglobinuria and haemosiderinuria.3,4

Bone marrow examination is not necessary to confirm the diagnosis but is recommended in patients with leukopenia and thrombocytopenia, to evaluate possible aplastic anaemia or myelodysplastic syndrome.1,4

These diagnostic and laboratory findings will allow the classification of patients into three groups based on the International PNH Interest Group recommendations.1,5

paroxysmal nocturnal haemoglobinuria pathophysiology- PNH diagnosis, classification of PNH

Learn more about the treatment options in PNH
and explore other PNH resources


  1. Parker CJ. Update on the diagnosis and management of paroxysmal nocturnal hemoglobinuria. Hematology Am Soc Hematol Educ Program. 2016; 2016 (1): 208–216. doi:10.1182/asheducation-2016.1.208
  2. Duval A, Frémeaux-Bacchi V. Complement biology for hematologists. Am J Hematol. 2023; 98 (Suppl 4): S5–S19. doi:10.1002/ajh.26855
  3. Barcellini W, Fattizzo B. Clinical applications of hemolytic markers in the differential diagnosis and management of hemolytic anemia. Dis Markers. 2015; 2015: 635670. doi:10.1155/2015/635670.
  4. Hill A, DeZern AE, Kinoshita T et al. Paroxysmal nocturnal haemoglobinuria. Nat Rev Dis Primers. 2017; 3: 17028. doi:10.1038/nrdp.2017.28
  5. Parker C, Omine M, Richards S et al. Diagnosis and management of paroxysmal nocturnal hemoglobinuria. Blood. 2005; 106 (12): 3699–3709. doi:10.1182/blood-2005-04-1717

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