Lab results can be confusing to patients and family members when discussing a new diagnosis of aHUS. Ask a lot of questions! It is vitally important that you understand the basic lab panels – you are the first in the “line of care” for yourself or your loved one and may often be called upon to give brief medical histories to medical personnel. Treatment options and frequency (more treatments, spacing out treatments, moving from plasma infusions to plasmapheresis, considering Soliris infusions) are choices that depend on trends seen in lab values in addition to the patient’s symptoms and ability to tolerate the chosen therapy.
The following are common lab tests ordered for aHUS patients. It is important for you to know whether the specific lab test is trending up or down or has stabilized from each lab draw to the next. Keeping a log, diary, or paper copy of lab values is helpful to many aHUS patients and their families.
Hemoglobin, hematocrit (’Crit): Together, these are the “H&H”; along with the red blood cell count, they relate to the ability of the patient’s blood to carry oxygen throughout the body. Higher lab values within the normal range are better since low numbers can indicate anemia, which may result in feeling tired or fatigued. If the patient has a low red blood cell count, doctors may choose to add a medication that can promote increased red blood cell production, such as erythropoietin (aka, “epo”) or a similar time-release drug called Aranesp® (darbepoetin alfa).
Platelets are cell fragments that help in the clotting process. If a patient has a low platelet count, their skin may more easily bruise, so black and blue marks should be reported to the medical team.
White blood cells (WBCs) are cells of the immune system involved in defending the body against infection. A high white blood cell count can mean that there is an infection.
Lactate dehydrogenase (LDH) is a chemical marker of aHUS disease activity, so a high number or upward trend usually means that the aHUS episode is worsening (“ramping up”), so treatment may need to be more aggressive.
Haptoglobin is another marker of hemolysis (the rupturing of red blood cells). When red blood cells break down, they release hemoglobin into the bloodstream. The hemoglobin combines with a chemical called haptoglobin. A low level of haptoglobin in the bloodstream is another indicator of active HUS.
Creatinine level indicates kidney function and is another vital laboratory value to monitor. Low creatinine numbers indicate that toxins are effectively being eliminated from the body through the kidney’s production of urine. High creatinine levels mean that the kidneys are not functioning properly and that toxins can build up in the body to dangerous levels. In end-stage renal disease (ESRD), the kidneys stop clearing toxins through urine output, so dialysis is needed to remove fatal levels of toxins from the patient’s body. Protein in the urine is another measurement of kidney function, as poorly functioning kidneys spill out too much protein.
Blood urea nitrogen (BUN) is a measurement of kidney function. It may also be impacted by how well hydrated a patient is and is an indicator of the kidney’s ability to keep body fluid levels normal. Lower BUN values are the desired trend.
Follow-up Lab Tests
Atypical HUS is characterized by repeated relapses, which can cause severe damage to vital organs, even though visible disease symptoms may be difficult to see at the onset of the disease. At the time of initial diagnosis, an aHUS patient will likely be hospitalized from weeks to months in order to closely monitor his or her condition, to consider and implement an effective treatment plan, and to assess both the variability and complexity of aHUS involvement. When the doctors feel the patient is healthy enough, they will begin to train the patient or parent in all aspects of home care and will set a care plan that includes follow-up appointments, lab work, and treatments.
Patient monitoring is particularly difficult because of the complexity, severity, and variability of the disease. A patient’s symptoms may also vary over time. Frequent lab tests can detect another episode before the patient experiences symptoms and can indicate the need for rapid treatment to protect kidney function during a relapse. Do not wait for distinct and pronounced symptoms, as often the only warnings will be a bit of tiredness, bruising, or perhaps vomiting. BE VERY PROACTIVE; ask for labs to be drawn at the first hint of any health or behavioral issues. Lab tests can often show aHUS activity BEFORE symptoms occur; do not wait for a follow-up or next scheduled appointment! Every aHUS patient is different, and no one can predict the disease’s course, so the most important goal is to aggressively monitor and treat patients in order to maintain the patient’s kidney function.