Ask the Expert: What blood work is common with Sjögren's and how often should it be performed?

"What blood work is common with Sjögren's and how often should it be performed?"
by Don Thomas, MD, FACP, FACR

In a person who has established Sjögren's,  we use labs to check disease activity, since these may be useful to see how the person does over time, assess how they respond to treatment, and help identify possible disease flares (increased disease activity). These tests include looking for low C3 and low C4 complement levels, elevated gammaglobulins (polyclonal gammopathy) on serum protein electrophoresis (SPEP), elevated cryoglobulins (proteins that clot easily in cooler temperatures), and elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). If cryoglobulins are negative, they are usually not repeated unless the person develops a problem commonly seen with them (such as inflammation of skin blood vessels, vasculitis). The others (C3, C4, SPEP, ESR, CRP) can be helpful to follow in some patients to assess disease activity. However, how often this should be done is unknown and varies widely between physicians. 

A complete blood cell count (CBC) can help see if there are any low blood counts related to the Sjögren's or if there is a side effect to any medications used to treat the Sjögren's. A metabolic (chemistry) panel can help follow the kidney function and to ensure there is no inflammation of the liver, which can occur in some Sjogren's patients. A urine sample along with a random urine protein-to-creatinine ratio is usually performed to see if there is any evidence of kidney inflammation from Sjögren's. Again, it is unknown how often these tests (CBC, chemistry panel, urine sample) should be done. 

 Some labs are performed if particular scenarios occur. For example, a creatine phosphokinase (CK or CPK) level may be checked in someone withmuscle weakness to see if that person muscle inflammation (myositis) from Sjogren's, but this is a rare problem. Thyroid function tests and vitamin B12 levels are also done in someone with fatigue to ensure that anunderperforming thyroid gland (hypothyroidism, such as from Hashimoto's thyroiditis) or vitamin B12 deficiency are not the causes. In the person with diarrhea, unexplained weight loss, or vitamin malabsorption, checking antibodies for celiac disease (also called gluten-sensitive enteropathy) is important since this appears to occur more often in people with Sjogren's. 

Approximately half of Sjögren's patients will develop an overlap syndrome with another systemic autoimmune disease (such as lupus or rheumatoid arthritis). Therefore, if any problems occur that can be seen in these disorders, labs that can be helpful in diagnosing them would be important to obtain. 

Some patients can have a high amount of one gammaglobulin on their SPEP (called a monoclonal gammopathy). If this occurs, we do a workup to ensure that the person doesn't have any type of cancer related to it (such as multiple myeloma), and we monitor their levels regularly. Fortunately, the vast majority of patients with this problem never develop cancer related to it. 

This article was first printed in  the Foundation's patient newsletter for members.