From the Guidelines
The primary test used to diagnose Paroxysmal Nocturnal Hemoglobinuria (PNH) is flow cytometry of peripheral blood cells, which detects CD55 and CD59 deficient clones. This method is considered the gold standard for diagnosing PNH, as it directly identifies the absence of GPI-anchored proteins on blood cells, a hallmark defect in the disease 1.
Key Diagnostic Features
- Flow cytometry of peripheral blood cells to detect CD55 and CD59 deficient clones
- Ham-Dacie and sucrose tests can be used where flow-cytometry is unavailable, although they are less sensitive and specific
Additional Supportive Tests
- Complete blood count (CBC) to assess for cytopenias
- Reticulocyte count to evaluate bone marrow response to hemolysis
- Lactate dehydrogenase (LDH) levels, which are typically elevated due to intravascular hemolysis
- Haptoglobin levels, which are usually decreased
- Urinalysis to detect hemoglobinuria
- Bone marrow examination may be performed to rule out other bone marrow disorders and assess for hypoplasia or aplasia
Importance of Early Diagnosis
Early and accurate diagnosis of PNH is crucial, as it can lead to life-threatening complications, including thrombosis, and effective treatments such as eculizumab or ravulizumab are available 1.
From the Research
Diagnostic Tests for Paroxysmal Nocturnal Hemoglobinuria (PNH)
To diagnose PNH, several tests can be used, including:
- Flow cytometric analysis of erythrocytes, granulocytes, and platelets using monoclonal antibodies to glycosylphosphatidylinositol-anchored proteins such as CD55 and CD59 2, 3
- Flow cytometric analysis of reticulocytes, which has been shown to be a sensitive diagnostic tool, especially for detecting small GPI-deficient populations 4
- Laboratory tests such as the acidified serum lysis (Ham) test, the sucrose lysis test, and the complement lysis sensitivity (CLS) test, although these tests are less specific and sensitive than flow cytometry 3
Flow Cytometry Markers
The most effective markers for flow cytometric diagnosis of PNH are:
- CD59 on erythrocytes and reticulocytes 2, 3, 4
- CD55 on erythrocytes, although its role as an independent diagnostic marker is questionable due to its lower sensitivity and specificity 2
- CD58 and CD59 on reticulocytes 4
- CD24/66b and FLAER on granulocytes 4
- CD14 on monocytes 4
Recommendations for PNH Diagnosis and Monitoring
PNH testing is recommended for patients with:
- Intravascular hemolysis
- Acquired bone marrow failure syndromes
- Thrombosis with unusual features 5 Flow cytometry is the gold standard for diagnosis and serial monitoring of PNH, and a screening panel of at least two different GPI-AP markers on granulocytes, erythrocytes, and reticulocytes is recommended 4