by Ernest H. Beutner, Ph.D.*
Professor of Microbiology and Dermatology,
University of Buffalo; School of Medicine and Biomedical Sciences;
Patients with pemphigus may benefit by working with their doctors to gain a better understanding of the tests used to detect and control the disease, in some situations. Three groups of tests can help doctors diagnose pemphigus; one of these can also help to control the disease. Two groups use skin or oral tissue samples, one from light microscopy and one for direct immunofluorescence. A third group uses blood tests for the pemphigus antibodies that cause the disease; these fluctuate with disease activity. Many doctors use al three methods to check all diagnoses of pemphigus; each test gives different types of information.
Part 1 of this series summarizes what these blood tests can show and lists the two evaluation programs that labs can use to check if they do them correctly. In running one of these programs, we find: a) most labs that check their tests do them well, b) some need to improve and c) some labs fail to check the quality of the blood tests they do. First we review what these tests can tell us about the diagnosis and treatment responses, if they are done correctly.
Diagnosis: Blood tests for pemphigus serve as highly sensitive diagnostic tests. The "titers" of these tests tell us the amount of antibody; low titers of 10, 20 or 40 need to be interpreted with caution. Almost all patients with active pemphigus give positive blood tests, usually with titers of 80 or more. If two repeat tests in an active phase of the disease give negative results, then three possibilities need to be considered: 1) False negative tests occur if they are not done correctly. 2) The patient may not have pemphigus; that is, the diagnosis may be wrong. 3) Reaction of blood sample may cause special problems; labs can usually see and explain such problems.
The selection of the type of blood tests depends, in part, on the type of pemphigus. Mucosal pemphigus can cause lesions of the mouth, nose, esophagus or genital mucous membranes often also affects the skin. [Medical terms: pemphigus vulgaris, pemphigus vegitans and paraneoplastic pemphigus]. To perform the blood tests properly, they need to be carried out on thin sections of monkey esophagus. Pemphigus of only the skin is usually less severe. [Medical terms: pemphigus foliaceus, pemphigus erythematosus and pemphigus herpetiformis cases]. Added blood tests are often needed since antibodies of these cases may not react with monkey esophagus; but guinea pig esophagus or human skin sections give positive blood tests in almost all-active cases.
Evaluations of treatment responses: Titers of blood tests go down when treatment is successful. If titer becomes negative, it indicates that the disease may be under control. Thus, some doctors ask for repeat blood tests to aid in checking on treatment responses. Labs that do such repeat tests need to keep the previous blood serum on file to compare with the new one.
Checks on blood tests for pemphigus: The reliability of these tests should be checked annually by all labs that do them. Two voluntary proficiency programs give labs certificates of participation, notably:
1) The Ernest Witebsky Center for Immunology of the University at Buffalo and Beutner Laboratories; P. O. Box 26, Buffalo, NY 14215-0026; Phone (716) 838-0549. All labs can use this program.
2) The Mayo Clinic; Attention, Dr. Arnold Schroeter; Department of Dermatology; Mayo Clinic; Rochester, MN 55905; Phone (507) 284-6891. Only dermatopathologists (ASDP members) can use this program.
You may wish to show this to your physician. If he/she is interested, Part II of this series in the next newsletter will give tips on how to work with your physician to check on the reliability of blood tests they order.
*Dr. Ernst Beutner and his team discovered the "pemphigus antibodies" which cause the disease in 1965. Because blood tests for pemphigus play a key role in the diagnosis, management and basic studies of the disease, he and his associates, Dr. Fang and Dr. Sofat continue to provide a non-profit quality control programs for them.