Autoimmune Labs 101

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Every few months, I present my antecubital space (the inside of my elbow) to my local lab personnel. We are on a first name basis these days, since they have been drawing my blood for five years now. How's the kids? Have a nice vacation? How about those Seahawks? 

John thinks that my familiarity with the lab department is a sad state of affairs, but I say if someone has to be inserting a large-gauge needle into my body, I want that person to be a friend. 

Within a few days I have my lab results. Early on in my diagnosis, I was a little fuzzy on the specifics of my labwork . After lots of discussions with Dr. S., and a little research on my part, I finally have a basic understanding of some of the measurements that my rheumatologist is looking for. 

Here's a brief overview of labwork specific to autoimmune disease. Remember that this is a very simplified explanation and any questions that you may have regarding your labs should always be discussed with your doctor. Diagnosis of an autoimmune disease is a complex process, and there is no one lab value that is diagnostic for autoimmune disease. The NIAMS (National Institute of Arthritis and Musculoskeletal Disorders) website explains the diagnostic procedure for Sjogren's Syndrome here: 

Your doctor will diagnose Sjögren’s syndrome based on your medical history, a physical exam and results from clinical or laboratory tests. While reviewing your medical history, your doctor will ask questions about your general health, specific symptoms you are experiencing, and medical problems you and your family members have or have had. Your doctor will also ask about any medications you are taking and about lifestyle habits such as smoking or alcohol consumption. During the exam, your doctor will check for clinical signs of Sjögren’s syndrome, such as indications of mouth dryness (described on page 7), or signs of other connective tissue diseases.

Diagnostic clinical testing such as Shirmer test, slit lamp testing, chest x-ray, urinalysis, and lip biopsies all contribute valuable information in evaluating a potential Sjogren's Syndrome patient. If you want to read more about these clinical tests, you can find more information here and here. 

A post describing every aspect of diagnosis of autoimmune disease would read like War and Peace, so in an effort to keep things simple, I'm just going to address the abnormalities that may present themselves in the blood of a person with Sjogren's Syndrome. Keep in mind that each disease within the autoimmune category has it's own effect on the body, and will impact lab values somewhat differently. 

When a patient makes their first visit to a doctor to be evaluated for Sjogren's Syndrome or other autoimmune diseases, the doctor will order several tests.  

Routine tests may include:

• CBC, or a complete blood count of red blood cells and the various white blood cells
• electrolyte panel, to check for blood elements such as calcium, sodium, chloride, magnesium, and sodium; 
• glucose and iron levels;
• bilirubin, to check for liver function;
• blood urea nitrogen and creatinine to measure kidney function;
• sedimentation rate and C-reactive protein, to measure inflammatory activity.
  

Immune system blood tests may include:

• immunoglobulins, which include three types of antibodies. In autoimmune disease, this level is elevated.
• rheumatoid factors are auto antibodies which attack the body's own healthy tissue. RF may be elevated in rheumatoid arthritis, Sjogren's Syndrome, and other autoimmune connective tissue diseases.
• anti-nuclear antibodies are auto antibodies which attack the cells' nuclei. The ANA may be elevated in Sjogren's Syndrome, lupus, and other autoimmune disease. A weakly positive ANA may also be present in otherwise healthy individuals. Conversely, a negative ANA may also be present in Sjogren's Syndrome. 
• Sjogren's antibodies, anti SS-A, (or - RO) and anti SS-B, (or - LA) are commonly found in patients with Sjogren's Syndrome and may be present in other autoimmune disease. 
• Complement is a system of proteins in the blood which work with the immune system and play a role in inflammation. Typically measured as C3 and C4, and usually normal in Sjogren's Syndrome, a decrease in complement may be an indicator of  the autoimmune disease Lupus. 
  

Want to learn more about these and other lab tests? You can read about them here, here, and here.