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.
Rheumatoid Factor (RF) Test
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
- The results of your RF test will be reported as units per milliliter (u/mL) or the concentration of the antibodies in your blood. Normal levels of RF antibodies in your blood are less than 40 to 60 u/mL, or a concentration under 1:80. Higher numbers indicate a positive RF result.
- Rheumatoid Arthritis is diagnosed using RF test and Anti-CCP test preliminary , Other tests which they are (ESR, CRP, and CBC) are used to indicate that the body in an inflammation status, also they assess in follow up in the treatment course.
- Once RF test results is above the normal value i.e. Positive RF, physician must diagnose the patient case as rheumatic and ask him to do Anti-CCP test which confirm rheumatic arthritis, once RA is confirmed, the doctor start medication prescription.
- Later, The Patient must take a blood sample for ESR, CRP, and CBC tests to help know the progress of the RA disease and effectiveness of the RA treatment. high values mean risks and low value especially gradually decreasing results are telling us that the patient in his way to heal.
- Anti-ds DNA test may be not used due to its low Specificity towards RA.
- Liver Enzymes may be Slightly elevated due to inflammation.
False Positive and Negative RF
- High RF means Rheumatoid Arthritis, However False Positive/Negative RF results still expected.
- While 80 percent of people with RA display this factor, 20 percent don’t. And 10 percent of people without rheumatoid arthritis test positive for RF due to hepatitis, leukemia, lupus, or other disorders such as Sjogren syndrome which is an autoimmune disorder that causes dry eyes and a dry mouth.
- RF may be Negative Falsely due to Lab Errors or interference with other analyses in the blood.
- For such reasons, the Ant-CCP test has more clinical Significance in diagnosis and prognosis of rheumatic Arthritis than RF, thus False Negative RF or False Positive results can be cleared.
- While ESR or C-reactive protein tests may provide an indication of rheumatoid arthritis, they cannot be a clear evidence of RA due to their high sensitivity towards many other inflammatory diseases, so they are used in follow up only.
- Special RF Symptoms help With lab test to confirm RA, Carpal tunnel syndrome, Sjogrens syndromeis, and Polyarthritis are diagnostic symptoms for RA.
If you know the RA symptoms, you may skip the next chapter and read the Blood tests explanation.
Symptoms are help prognosis with Lab tests.
Organs affected by RA:
Most of the time, RA usually affects joints on both sides of the body equally. Wrists, fingers, knees, feet, and ankles are the most commonly affected.
Early symptoms and Slowly: may include morning stiffness and minor pain in symmetrical joints (Polyarthritis ) for more than one hour, and fatigue.
Later, Feeling worm tender swelled joints with redness and joint stiff when not used for an hour.
Lately, Joints deformed and locked over time which means lose their range of motion with other complications and symptoms which include:
•Eye burning, itching, and discharges
•Nodules under the skin which mimic that of Gout and other sever diseases.
•Sleep difficulties due to night pain.
•Pleurisy: Chest pain when taking a breath.
•Autoimmune syndromes and disorders such as Sjogrens syndrome and carpal tunnel syndrome.
1- Sjogrens syndrome: an autoimmune disorder that can cause dryness of the eyes, mouth, nose, throat, or skin due to inflammation that stops glands from releasing moisture.
2- carpal tunnel syndrome: Numbness, tingling, or burning in the hands and feetThere are Complicated Signs and Symptoms with other diseases such as osteoarthritis, or something as serious as cancer. Or you may simply have a bad mattress.
Read The Article Carefully to know How RA is Diagnosed with Lab tests?
- Diagnostic Blood Tests for Rheumatoid Arthritis are Serum RF, Serum Anti-CCP (if RF Positive), CBC, C-RP, and ESR.
- Reference ranges of some tests may be different in laboratories due to different testing methods and instrumentations.
- Additional investigations may include: Synovial fluid analysis and/or joint ultrasound, MRI, and X-rays to help track the progression of rheumatoid arthritis in your joints over time.
- False Results are managed by a Professional Lab Technologist or Experienced Clinical Doctor.