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Monitoring your blood
Regular blood testing will help avoid unpleasant surprises
By Edward Tenner, MD
PPS Contributing Editor
People living with pemphigus and pemphigoid have to carefully check for problems related to the many medications they need to take to control their disease. I will try to go through most of the medications used and discuss which blood tests should be done. Since each person is different this is only a guild line and anyone should check with their own doctors if there are any questions.
In looking for pemphigus or pemphigoid, certain blood tests may help in making the diagnosis. A blood test for antiepidermal antibodies against intercellular substance will be positive in pemphigus and pemphigoid. Normal is a titer of less than 1:20.
These autoantibodies can be looked at more specifically with ELISA tests for desmoglein 1 and 3. These tests, which can be done at some university centers, help to make the diagnosis of pemphigus and differentiate pemphigus vulgaris from pemphigus foliaceus.
Also before starting therapy, evaluating the following blood tests should be considered: complete blood count (CBC) with differential, electrolytes, BUN, creatinine, liver function tests, fasting blood glucose, antinuclear antibody (ANA). Other tests that may needed are: chest X-ray, urinalysis, blood pressure, and bone density monitoring. For each of the following medications certain blood tests should be considered.
Azathioprine (Imuran)
Before starting this medication some doctors like to check the thiopurine methyltransferase (TPMT) level. If it’s very low, azathioprine is best avoided, if low, reduced dosage should be used, and if high, a standard dose may under-treat.
When using azathioprine, a complete blood count and platelet count should be performed every 4 to 6 weeks. Also, the liver function tests aspartate aminotransferase and alanine aminotransferase should be performed every 12 weeks. If the liver tests are abnormal the dose should be reduced and retested. If markedly elevated the drug should be stopped.
Chlorambucil (Leukeran)
A complete blood count should be checked on patients receiving chlorambucil therapy. Initially a CBC should be performed weekly. Once a stable dose has been achieved, the frequency of monitoring may be reduced to monthly. For patients on short-term, high-dose chlorambucil, weekly monitoring is required throughout, as the dose is being escalated.
Cyclophosphamide (Cytoxan)
For oral therapy, a complete blood count, platelet count, and urinalysis should be obtained weekly initially and, when dosing is stable, at least every 4 weeks. If the CBC decreases the dose should be lowered or stopped. If the urinalysis shows hematuria (blood in the urine) the medication should be stopped, and if not resolved in a month, a urologist should be consulted.
Cyclosporine (Sandimmune or Neoral)
Serum creatinine should be checked every 2 weeks initially and monthly once dosage has stabilized. Also BUN, serum bilirubin and liver function tests need repeat assessment. Serum concentrations of the drug can monitor serum absorption, but they don’t correlate well with efficacy for autoimmune disorders.
Dapsone
G6PD level needs to be checked before starting therapy, because people who are G6PD deficient are more susceptible to developing anemia (low red blood cell count.) Because this drug causes the destruction of red blood cells and leads to anemia, and can also affect white blood cell production, a CBC with differential needs to monitored every 2 weeks for the first 3 months then every 3 months.
Gold Compounds (Auranofin, Aurothiogluose)
Before starting perform CBC with differential and platelet count, renal and liver function tests, also urinalysis. When on medication repeat CBC and platelet counts every 2 weeks. Periodic rechecking of renal and liver function tests is needed to look for these possible side effects.
Methotrexate (Rheumatrex)
At the initiation of methotrexate therapy, a complete blood count, serum chemistry profile, hepatitis B surface antigen, and hepatitis C antibody should be obtained. Complete blood count and liver function tests need to be checked every 1 to 2 months. If the liver function tests (aspartate amino-transferase or alanine aminotransferase) are more than two times normal on two separate occasions, the dose should be reduced. Liver biopsy should be done if abnormalities in liver function tests persist after discontinuation of the drug.
Mycophenolate Mofetil (CellCept)
Patients should be checked with complete blood counts on a weekly basis for 4 weeks, then on a twice monthly basis for 2 months, with monthly testing thereafter. Liver function tests should be tested every 3 months.
Prednisone and other glucocorticoids
Monitor blood pressure, weight, and check fasting blood glucose every 3 months. A blood test for lipids (cholesterol and triglycerides) should be checked annually. Bone density (Dexa-scan) within the first 3 months of starting treatment and annually thereafter.
Tetracycline and Doxycycline (Monodox)
With long term therapy periodic CBC, liver function tests and BUN and creatinine testing should be done.
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