PNH is rare, and the symptoms can be similar to those of other diseases, so it can be a challenge to diagnose.
Many different blood tests are used to help diagnose PNH, each of which provides valuable clues.
Flow cytometry is widely considered the most informative way to confirm a PNH diagnosis. It detects if red blood cellsred blood cellsThe most common type of blood cell. Their job is to carry oxygen using an important molecule, hemoglobin, around the body. are missing their protective shield, a key sign of PNH. It also calculates the quantity of blood cells impacted by PNH, which is called your “clone size.” If you have a large clone size, it means you have a high percentage of blood cells that may be destroyed, which may lead to more severe symptoms.
Measures the total amount of bilirubin (a pigment produced from the destruction of red blood cells) in your blood. People with PNH may have high levels of bilirubin.
Complete blood count (CBC)
Analyzes the amount of red and white blood cells, hemoglobin and platelets in your blood. For people with PNH, red blood cell and hemoglobin levels are typically lower than normal.
Lactate dehydrogenase test (LDH)
Determines the amount of LDH (an enzyme) found in your blood. Red blood cell destruction results in the release of LDH into the blood. People with PNH often have higher levels of LDH.
Absolute reticulocyte count (ARC)
Measures the amount of young red blood cells in your blood. High reticulocyte counts can be a sign of red blood cell destruction, as the body is constantly making new red blood cells to replace the ones being destroyed by the immune system.
Measures the amount of haptoglobin in the blood. Haptoglobin is a proteinproteinsLarge, complex molecules that play many important roles in the body and can be thought of as the “workhorses” of cells. Proteins are required for the structure, function and regulation of the body’s organs and tissues. that attaches to hemoglobinhemoglobinThe critical protein found inside red blood cells that enables other cells throughout the body to get the oxygen they need. Hemoglobin acts like drops of glue that can “stick” to oxygen and carry it from the lungs to other tissues. It can also “stick” to waste like carbon dioxide to help remove it from the body. once it has been released from red blood cells. People with PNH typically have low haptoglobin levels.
Making sense of the numbers
The goal of treatment in PNH is to prevent destruction of red blood cells. While there is no formal standard for exactly what numbers represent “normal” levels across the various tests used to assess destruction, many doctors consider a combination of factors to be the best gauge.
For example, your doctor may consider lab results for hemoglobin, LDH and ARC levels in combination with the number of transfusions in the past 12 months.