Poor prognostic factors include,

- Persistent synovitis

- Early erosive disease

- Extra-articular findings (including subcutaneous rheumatoid nodules)

- Positive serum RF findings

- Positive serum anti-CCP autoantibodies

- Carriership of HLA-DR4 "Shared Epitope" alleles

- Family history of RA

- Poor functional status

- Socioeconomic factors

- Elevated acute phase response (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP])

- Increased clinical severity.

When RA is clinically suspected, a physician may test for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs measured as anti-CCP antibodies).

It is positive in 75-85%, but a negative RF or CCP antibody does not rule out RA, rather, the arthritis is called "seronegative", which is in about 15-25% of people with RA. During the first year of illness, rheumatoid factor is more likely to be negative with some individuals becoming seropositive over time. RF is a non-specific antibody and seen in about 10% of healthy people, in many other chronic infections like hepatitis C, and chronic autoimmune diseases such as Sjögren's syndrome and systemic lupus erythematosus. Therefore, the test is not specific for RA.

Hence, new serological tests check for anti-citrullinated protein antibodies ACPAs . These tests are again positive in 61-75% of all RA cases, but with a specificity of around 95%. As with RF, ACPAs are many times present before symptoms have started.

The by far most common clinical test for ACPAs is the anti-cyclic citrullinated peptide (anti CCP) ELISA. In 2008 a serological point-of-care test for the early detection of RA combined the detection of RF and anti-MCV with a sensitivity of 72% and specificity of 99.7%.

Other blood tests are usually done to differentiate from other causes of arthritis, like the erythrocyte sedimentation rate (ESR), C-reactive protein, full blood count, kidney function, liver enzymes and other immunological tests (e.g., antinuclear antibody/ANA) are all performed at this stage. Elevated ferritin levels can reveal hemochromatosis, a mimic of RA, or be a sign of Still's disease, a seronegative, usually juvenile, variant of rheumatoid arthritis.

Diagnosis of JIA is difficult because joint pain in children can be from many other causes. No single test can confirm the diagnosis, and most physicians use a combination of blood tests, X-rays, and clinical presentation to make an initial diagnosis of JIA. The blood tests measure antibodies and the rheumatoid factor. Unfortunately, the rheumatoid factor is not present in all children with JIA. Moreover, in some cases, the blood work is somewhat normal. X-rays are obtained to ensure that the joint pain is not from a fracture, cancer, infection, or congenital abnormality.

In most cases, fluid from the joint is aspirated and analyzed. This test often helps in making a diagnosis of JIA by ruling out other causes of joint pain.

Early diagnosis and treatment by a paediatric rheumatologist or a rheumatologist can help manage inflammation, relieve pain, and prevent joint damage. Careful examination, laboratory tests (blood and urine), and various forms of imaging like X-rays may be some of the tests conducted by a doctor.

Although there are no definitive criteria to diagnose the existence of reactive arthritis, the American College of Rheumatology has published sensitivity and specificity guidelines.

Diagnosis is made by clinical examination from an appropriate health professional, and may be supported by other tests such as radiology and blood tests, depending on the type of suspected arthritis. All arthritides potentially feature pain. Pain patterns may differ depending on the arthritides and the location. Rheumatoid arthritis is generally worse in the morning and associated with stiffness; in the early stages, patients often have no symptoms after a morning shower. Osteoarthritis, on the other hand, tends to be worse after exercise. In the aged and children, pain might not be the main presenting feature; the aged patient simply moves less, the infantile patient refuses to use the affected limb.

Elements of the history of the disorder guide diagnosis. Important features are speed and time of onset, pattern of joint involvement, symmetry of symptoms, early morning stiffness, tenderness, gelling or locking with inactivity, aggravating and relieving factors, and other systemic symptoms. Physical examination may confirm the diagnosis, or may indicate systemic disease. Radiographs are often used to follow progression or help assess severity.

Blood tests and X-rays of the affected joints often are performed to make the diagnosis. Screening blood tests are indicated if certain arthritides are suspected. These might include: rheumatoid factor, antinuclear factor (ANF), extractable nuclear antigen, and specific antibodies.

There is no definitive test to diagnose psoriatic arthritis. Symptoms of psoriatic arthritis may closely resemble other diseases, including rheumatoid arthritis. A rheumatologist (a doctor specializing in autoimmune diseases) may use physical examinations, health history, blood tests and x-rays to accurately diagnose psoriatic arthritis.

Factors that contribute to a diagnosis of psoriatic arthritis include the following:

- Psoriasis in the patient, or a family history of psoriasis or psoriatic arthritis.

- A negative test result for rheumatoid factor, a blood factor associated with rheumatoid arthritis.

- Arthritis symptoms in the distal Interphalangeal articulations of hand (the joints closest to the tips of the fingers). This is not typical of rheumatoid arthritis.

- Ridging or pitting of fingernails or toenails (onycholysis), which is associated with psoriasis and psoriatic arthritis.

- Radiologic images demonstrating degenerative joint changes.

Other symptoms that are more typical of psoriatic arthritis than other forms of arthritis include enthesitis (inflammation in the Achilles tendon (at the back of the heel) or the plantar fascia (bottom of the feet)), and dactylitis (sausage-like swelling of the fingers or toes).

There are few clinical symptoms, but the clinical picture is dominated by arthritis in one or more joints, resulting in pain, swelling, redness, and heat sensation in the affected areas.

The urethra, cervix and the throat may be swabbed in an attempt to culture the causative organisms. Cultures may also be carried out on urine and stool samples or on fluid obtained by arthrocentesis.

Tests for C-reactive protein and erythrocyte sedimentation rate are non-specific tests that can be done to corroborate the diagnosis of the syndrome.

A blood test for the genetic marker HLA-B27 may also be performed. About 75 percent of all the patients with Reiter's arthritis have this gene.

New research shows that identifying what type of JIA a child has can help target treatment and lead to more positive outcomes. Identifying the specific biomarkers related to each type of JIA can help form more personalized treatment plans and decrease remission rates.

Children with JIA are more susceptible to cardiovascular disease, depression, sleep disturbance, anxiety and fatigue than healthy individuals. There is also limited information that suggests that children with JIA are at increased risk for malignancies when being treated with TNF blockers.

Prognosis is more positive when gene testing is undergone to identify what subtype of JIA is present in the child. Standardized treatment protocols are in place specific to each subtype of JIA. Treatment is more successful when targeted to the specific subtype of JIA.

Inflammatory arthritis can be disabling to the point where people with the diseases can lose their jobs, which can cause psychological distress. Because it is typically progressive, those who lose their jobs are unlikely to re-enter the workforce after leaving due to their diagnosis. Programs now aim to retain those with inflammatory arthritis by preventing work-related injuries and by making necessary accommodations in the workplace. A 2014 Cochrane review found low-quality evidence that work focused interventions, including counseling, education, advocacy, and occupational medicine consultations, were effective in retaining workers with inflammatory arthritis.

Several conditions can mimic the clinical presentation of psoriatic arthritis including rheumatoid arthritis, osteoarthritis, reactive arthritis, gouty arthritis, systemic lupus erythematosus, and inflammatory bowel disease-associated arthritis. In contrast to psoriatic arthritis, rheumatoid arthritis tends to affect the proximal joints (e.g., the metacarpophalangeal joints), involves a greater number of joints than psoriatic arthritis, and affect them symmetrically. Involvement of the spinal joints is more suggestive of psoriatic arthritis than rheumatoid arthritis. Osteoarthritis shares certain clinical features with psoriatic arthritis such as its tendency to affect multiple distal joints in an asymmetric pattern. Unlike psoriatic arthritis, osteoarthritis does not typically involve inflammation of the sacroiliac joint. Psoriatic arthritis sometimes affects only one joint and is sometimes confused for gout or pseudogout when this happens.

When faced with monoarthritis, one of the main decisions to make is whether to perform a "joint aspirate" by inserting a needle into the affected joint and removing some fluid for microscopic analysis. This decision is largely taken on inflammatory markers in blood tests (e.g. CRP), fever and the clinical picture. The main use of aspiration is to detect bacteria and neutrophil granulocytes (in septic arthritis) and crystals (crystal arthropathies).

Due to the symptoms of palindromic arthritis and the nature of the attacks, diagnosis can be difficult or take a long time. The symptoms can be similar to many other forms of arthritis or other autoimmune diseases. It is often a case of eliminating the other conditions before getting the correct diagnosis due to there being no specific test for PR diagnosis.

No single test can confirm a diagnosis. A doctor may make a diagnosis based on medical history and signs and symptoms. Palindromic rheumatism must be distinguished from acute gouty arthritis and an atypical, acute onset of rheumatoid arthritis (RA). Without specific tests (such as analysis of joint fluid), it may be difficult to distinguish palindromic rheumatism from other episodic joint problems. It is important to note that a person may experience more than one autoimmune disorder at the same time. Laboratory findings are usually normal. Blood tests may show an elevation of the ESR and CRP, but are otherwise unremarkable. Rheumatoid factor may be present especially in the group that is likely to develop rheumatoid arthritis.

Arthritis mutilans' parent condition psoriatic arthritis leaves people with a mortality risk 60% higher than the general population, with premature death causes mirroring those of the general population, cardiovascular issues being most common. Life expectancy for people with psoriatic arthritis is estimated to be reduced by approximately 3 years.

The treatment of juvenile arthritis includes medications, physical therapy, splints and in severe cases surgery. These treatments are focused on reducing swelling, relieving pain and maintaining full movement of joints. Children are encouraged to be involved in extra-curricular activities, physical activity when possible, and to live a "normal" life.

Rheumatoid factor and ANA tests are generally negative in systemic JIA.

Lab findings: anemia of chronic disease, neutrophilia, thrombocytosis, elevated acute phase reactants (ESR, CRP, ferritin).

There is no known cure for either rheumatoid or osteoarthritis. Treatment options vary depending on the type of arthritis and include physical therapy, lifestyle changes (including exercise and weight control), orthopedic bracing, and medications. Joint replacement surgery may be required in eroding forms of arthritis. Medications can help reduce inflammation in the joint which decreases pain. Moreover, by decreasing inflammation, the joint damage may be slowed.

Laboratory testing includes white blood cell count, ESR, and CRP. These values are usually elevated in those with septic arthritis; however, these can be elevated by other infections or inflammatory conditions and are, therefore, nonspecific. Procalcitonin may be more useful than CRP.

Blood cultures can be positive in up to half of patients with septic arthritis.

25% of cases progress to severe destructive arthritis. In the United States and Canada, mortality is estimated at about 4% and in Europe, mortality is estimated at 21.7%.

The bone edema in arthitis mutilans can be treated with TNF inhibitors in the short term: a 2007 study found that the bone edema associated with psoriatic arthritis (of which arthitis mutilans is a subtype) responded to TNF inhibitors with "dramatic" improvement, but the study was not determinative of whether TNF inhibitors would prevent new bone formation, bone fusion, or osteolysis (bone resorption).

Assessment of Spondylarthritis International Society (ASAS criteria) is used for classification of axial spondyloarthritis (to be applied for patients with back pain greater than or equal to 3 months and age of onset less than 45 years). It is of two broad types:

1. Sacroiliitis on imaging plus 1 SpA feature, or

2. HLA-B27 plus 2 other SpA features

Sacroiliitis on imaging:

- Active (acute) inflammation on MRI highly suggestive of SpA-associated sacroiliitis and/or

- Definite radiographic sacroiliitis

SpA features:

- Inflammatory back pain

- Arthritis

- Enthesitis

- Anterior uveitis

- Dactylitis

- Psoriasis

- Crohn's disease or ulcerative colitis

- Good response to NSAIDs

- Family history of SpA

- HLA-B27

- Elevated CRP

Imaging such as x-ray, CT,MRI, orultrasoundarenonspecific. They can help determine areas of inflammation but cannot confirm septic arthritis.

When septic arthritis is suspected,x-raysshould generally be taken. This is used to assess for involvement of surrounding structures such as bone and also for comparison purposes when future x-rays are taken.While x-rays may not be helpful early in the diagnosis/treatment, they may show subtle increase in joint space and tissue swelling. Later findings include joint space narrowing due to destruction of the joint.

Ultrasoundcan be done and is effective at detecting joint effusions.

CTandMRI are not required for diagnosis but can be used if diagnosis is unclear or in joints that are hard to examine (ie.sacroiliacorhip joints). They can can help assess for inflammation/infection in or about the joint (ie.osteomyeltis).

The worldwide prevalence of inflammatory arthritis is approximately 3%. Rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and undifferentiated spondyloarthritis are the most common subtypes of inflammatory arthritis. The diseases occur most commonly in the 30-40 age group.

Worldwide prevalence of spondyloarthropathy is approximately 1.9%.

Sacroiliitis can be somewhat difficult to diagnose because the symptoms it manifests can also be caused by other, more common, conditions. If a physician suspects sacroiliitis, they will typically begin their diagnosis by performing a physical exam. Since the condition is axial, they can often pinpoint the affected joint by putting pressure on different places within the legs, hips, spine and buttocks. They may also ask a patient to perform some stretches that will put gentle stress on the sacroiliac joints.

X-rays, MRIs and other medical imaging tests can be used to show signs of inflammation and damage within the SI joints. Typically, a spine specialist will order a medical imaging test if they suspect ankylosing spondylitis or another form of arthritis to be the primary cause of inflammation and pain.