Rheumatoid Arthritis Blood tests and Normal Ranges
Laboratory diagnosis must contain all tests that help understand exactly the body status of the patient, also lab test results must come to clearly state the reasons of most complains.
Recommended Blood Tests to diagnose RA:
Serum Rheumatoid Factor test (RF), Anti-CCP are tests better diagnosing RA disease.
CBC, CRP, and ESR are tests help in confirming inflammation of the body’s tissues.
The time required to receive results: usually tests take from 1 hour up to 6 hours.
Fasting for 6 hours is Preferred before going to the lab.
Costs of RA tests panel vary from lab to lab and thus cannot be mentioned here.
Normal Value of RF test:
Agglutination method: Less than 1:80 titer, i.e. 1:80 is RF Positive
Quantitative RF and semi-quantitative test: Less than 40 – 60 u/mL “differs for each lab”.
■ RF is the Main Blood Test for rheumatoid arthritis (RA) because RF is the most relevant antibody (70 – 90 %) in case of RA. However other tests and symptoms must confirm RF results, keep reading.
■ RF is autoantibody that’s directed against organism’s own tissues.
RF antibody attaches to immunoglobulin G (IgG). antibodies that collect in the synovium of the joint. These antibodies are present in about 80 percent of RA patients.
■ Also elevated in collagen vascular diseases, infections, cancer,
Complete Blood Count (CBC):
A routine blood test which is predominantly requested for most patients.
CBC give Information about general health.
CBC test is a monitor of blood components and blood related diseases,
CBC NOT Required the Patient to be fast.
Patients of RA exhibit Abnormally low hemoglobin (Hb) level and hematocrit (HCT) Percentage in their CBC blood test.
Hgb Normal Ranges:
Male: 13–18 g/dL = 130–180 g/L
Female: 12–16 g/dL = 120–160 g/L
Hematocrit Normal Ranges:
Male: 45–52% = 0.45–0.52
Female: 37–48% = 0.37–0.48
CRP Blood Test:
Stands for C-Reactive Protein, Lab Technologist carry out CRP test on A drops of your blood, CRP is more inflammation sensitive that ESR, Also CRP is helpful with ASOT test.
C-reactive Protein (CRP); High-sensitivity CRP (hs CRP), Some labs require a fasting sample.
Normal Range: Less than 10 mg/L; SI units: 10 mg/L
■ Abnormal protein manufactured in the liver in response to
inflammation and infection. Useful in evaluating
autoimmune and infectious diseases and in monitoring
■ CRP levels usually rise to 100 mg/L or more in the presence
of inflammation and infection. For this purpose, the plain
CRP test is used because it measures CRP in the 10–1000
■ The high-sensitivity CRP test is used to assess risk of
atherosclerosis in otherwise healthy adults. It measures
CRP in the 0.5–10 mg/L range. Higher levels within this
range are associated with an increased risk of
ESR Blood Test:
Erythrocyte Sedimentation Rate is the long form, also called a ‘sed rate’.
A sample of Blood is put in a tube and left the RBCs to be settled in the bottom of the tube, Fasting is Preferred.
Adults (Westergren method): Males under 50 yr: 15 mm/hr. Males:
over 50 yr: 20 mm/hr. Females under 50 yr: 20 mm/hr; Females
over 50 yr: 30 mm/hr.
Children (Westergren method): Newborn: 0 to 2 mm/hr; 6 mo–to 12
yr: 3–13 mm/hr.
A high erythrocyte sedimentation rate may indicate inflammation in the joints
■ Measures the rate at which red blood cells settle in saline or plasma at the bottom of a test tube. In certain disease states (inflammation, infection, cancer), erythrocytes stack together, increasing their weight and the rate at which they settle.
Volume precipitated in the bottom is measured every one hour, and this called the ESR for first hour and ESR for second hour, etc. Thus,
increased sedimentation rate is an indicator of these diseases/conditions.
■ Used to monitor inflammatory or malignant disease,
rheumatic fever, and heart attack.
■ Useful in monitoring tuberculosis, tissue necrosis,
rheumatologic disorders, and other diseases.
People with rheumatoid arthritis tend to have an elevated erythrocyte sedimentation rate.
Rheumatoid Arthritis Prognosis and Confirmation Tests:
Autoantibodies are proteins created by the immune system that attack the body’s own tissues or organs.
■ Autoantibodies represent a failure by the immune system to distinguish between foreign proteins and the body’s own tissues.
■ Elevated autoantibody levels are found in people with autoimmune disorders such systemic lupus erythematosus (SLE).
■ Used to Confirm Auto-Immunological diseases Such as RA, and SLE.
1- Blood test for Serum anti-CCP:
Anti-CCP or ACPAs is for anti-cyclic citrullinate d peptide antibodies.
Most testing kits of Anti-CCP are immunoassays which have excellent performance with sensitivity between 69.6% and 77.5% and a specificity between 87.8% and 96.4%.
Anti-CCP test is more specific than rheumatoid factor and used to distinguish various causes of arthritis. Also ACPAs tests are useful for monitoring disease activity and effects of RA therapy.
the same antibody specificity has been described as anti-keratin antibodies (AKA) and anti-perinuclear factor (APF).
ACPAs have proved to be powerful biomarkers that allow the diagnosis of rheumatoid arthritis (RA) to be made at a very early stage.
Anti-CCP is also very useful in the early diagnosis of rheumatoid arthritis in high-risk groups, such as relatives of RA patients (concordance rate of developing RA 3.6 – 15.4% of among twins).
The reference ranges for blood tests of anti–citrullinated protein antibodies are:
Negative: < 20 EU
Low/weak positive: 20 – 39 EU
Moderate positive: 40 – 59 EU
High/strong positive: > 60 EU
2- DNA antibodies (anti-double-stranded DNA)
1:20 or 1:40 equivocal
>1:80 supports diagnosis of SLE
Anti-ds DNA is positive at 1:80 or higher in 60-80% of SLE. Low titres may be seen in rheumatoid arthritis, autoimmune hepatitis and in other immunological disorders.
Interpretation of Rheumatoid Arthritis blood test results
False Positive and Negative RF