The initial diagnosis of atypical hemolytic uremic syndrome (aHUS) — a rare, progressive disease characterized by hemolytic anemia, or the destruction of red blood cells, and a low platelet count, called thrombocytopenia — is done through a blood test.
Therefore, it’s helpful for patients to understand what those blood test results mean. People with aHUS also may wish to know more about the different blood parameters implicated in this disease, which results in kidney failure.
Know your blood test report
To start, doctors usually order a complete blood count (CBC) test that measures several parameters in the blood. These include the quantities of red blood cells, called RBCs or erythrocytes, white blood cells, known as WBCs or leukocytes, and platelets, also called thrombocytes. The CBC also measures the levels of hemoglobin — the protein that carries oxygen in RBCs — and hematocrit, which is the ratio of RBCs to total blood volume.
The resulting report also may contain information about the levels of proteins and other components dissolved in the blood, such as haptoglobins, albumin, creatinine, and blood urea nitrogen, called BUN.
Understanding the results of your complete blood count test report is the first step in trying to gauge the severity of aHUS.
Not all lab reports are equal
An important thing to note is that lab reports from different labs for the same test may not be exactly the same. Many factors — such as the instruments and substances, or reagents, used in the testing, as well as handling differences — can influence the results. An individual’s report contains reference ranges for the tested parameters that have been standardized and validated for that particular diagnostic lab. Test values should always correlate only with those reference ranges.
Low hemoglobin level and RBC counts
Normal hemoglobin levels for adult males is 14-17.5 g/dL, while it ranges between 12.3-15.3 g/dL for females. In aHUS, hemoglobin levels may fall to less than 10 g/dL, which indicates an anemic condition. With anemia, the body lacks enough healthy red blood cells to carry adequate oxygen to its tissues.
Decreases in hemoglobin correlate with decreases in RBC counts. A normal adult male has about 4.5-5.9 million RBCs in one microliter of blood, while normal adult females can have between 4.1 and 5.1 million RBCs per microliter. Significantly lower values than these indicate anemia.
Low platelet counts
The normal platelet count in a healthy individual ranges from 150,000 to 450,000 platelets per microliter of blood. In aHUS, the values fall to less than 150,000 platelets per microliter, resulting in a condition called thrombocytopenia. People with this condition have a low blood platelet count. Platelets stop bleeding by clumping and forming plugs in blood vessel injuries.
Elevated biochemical parameters
Certain biochemical parameters — including lactate dehydrogenase (LDH) levels, creatinine, and BUN — are elevated in aHUS when compared with healthy individuals. LDH levels increase when RBCs break down. Increases in creatinine and BUN levels indicate kidney damage.
aHUS is marked by the kidneys’ inability to process waste products from the blood and excrete them into the urine (acute kidney failure), a condition known as uremia.
Last updated: September 10, 2019
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