Decoding Your Psoriatic Arthritis Bloodworkby Casey Nilsson Patient Advocate
Your rheumatologist has ruled out a litany of other diseases and it’s finally settled: You have psoriatic arthritis. But just when you thought your witty repartee with your phlebotomist has come to an end, not so fast: In addition to regular X-rays, your doctor will monitor your psoriatic arthritis disease activity — mainly: the presence of inflammation in its varied forms, which leads to skin lesions, join pain, and joint damage — with bloodwork every three months to once a year, depending on your prognosis. Read on to learn more.
CBC With Auto Differential
A standard blood test, the complete blood count (CBC) with auto differential will be exactly what the doctor orders. You’re likely familiar with the CBC; most primary care physicians administer it after a physical to check your overall health. The auto differential monitors inflammation and immune system cells by testing the percentage of neutrophils, lymphocytes, monocytes, eosinophils, and basophils in your blood. (More on those later.)
Erythrocyte Sedimentation Rate
Your doctor will use the ESR, a.k.a. sed rate, blood test to monitor your chronic inflammation levels. The test captures how quickly your red blood cells settle at the bottom of a tube; the standard range for this test is between zero and 20 millimeters per hour. The sed rate test also helps doctors determine how well your course of treatment — from non-steroidal anti-inflammatories like ibuprofen to disease-modifying drugs such as biologics — is working.
The C-reactive protein test is also administered to monitor inflammation levels, however it tends to capture acute inflammation. The standard range is between zero milligrams of C-reactive protein per liter of blood to 10 MG/L.
White and Red Blood Cell Counts
A high white blood cell count could also indicate inflammation. A low red blood cell count indicates anemia, a common psoriatic arthritis comorbidity. Your rheumatologist may also check your total iron levels in a blood test independent from the CBC. Anemia in psoriatic arthritis is especially important to catch, as most patients already have some level of fatigue due to the presence of cytokines, proteins released during inflammatory reactions.
Lymphocytes (also known as T- and B-cells) are white blood cells that moderate the body’s immune response. T-cells are responsible for releasing the cytokines that cause fatigue in many psoriatic arthritis patients without anemia. A normal lymphocytes range is between 18-45 percent of total white blood cells, and a low lymphocyte count can point to an autoimmune condition or the immunosuppressive drugs that treat it.
This type of white blood cell responds to, and fights, infections. A low neutrophils count (less than 2,500 per microliter of blood) signals an overactive immune system and points to the presence of an infection or an autoimmune disorder. Low neutrophil count (neutropenia) can occur as a result of some medications that are used to treat psoriatic arthritis, and your doctor would consider this as well if neutropenia is present.
Also a white blood cell, monocytes help the body fight disease and repair after an immune response. A high percentage of monocytes — more than 10 percent — signals the presence of disease.
Your rheumatologist may also check your eosinophils, a white blood cell that fights allergy and infection-related inflammation. If eosinophils build up — an absolute count of more than 350 — an absolute count of more than 350, this can reflect an allergic or inflammatory process that your body is dealing with.
This white blood cell fights invaders such as parasites but also indicates chronic or acute inflammation. (It’s also responsible for releasing histamine, the allergy compound.) A basophils count between zero and 2 percent is optimal.
The Bottom Line
Psoriatic disease is all about inflammation. If your levels are high, speak with your doctor about ways to reduce your chronic inflammation through prescribed medications, diet, and lifestyle changes. Systemic inflammation worsens psoriatic arthritis and may lead to other diseases, including heart disease, obesity, and depression, so it’s best to keep tabs on your levels and work together to get it under control.