Rheumatology Diagnostics 10/1/25

Flashcards related to key terms and concepts from rheumatology diagnostics lecture notes.

Histochemistry

A technique used for the differential staining of cells and tissues based on the chemical differences of their parts.

Immunofluorescence

A technique that uses fluorescent dye to identify specific antigens or proteins in a cell or tissue sample.

Ex) ANA testing via indirect immunofluorescence

Acute Phase Reactants

Substances whose levels increase in response to inflammation, associated with infections, trauma, and autoimmune diseases. (acute and chronic inflammatory states)

acute phase reactant labs

ESR, CRP, ferritin

Erythrocyte Sedimentation Rate (ESR)

Rate at which erythrocytes suspend in plasma fall when placed in a vertical tube.

Units: mm/hr

Nonspecific test

If elevated:

• Systemic and localized inflammatory or infectious disease

• Malignant neoplasms

• Tissue injury/ ischemia

• Trauma

If decreased:

Technical factors: Clotting of sample, Delay in testing > 2hrs, Room temperature

C-Reactive Protein (CRP)

Nonspecific acute phase reactant used to indicate inflammatory illness

Units: mg/dL

More sensitive and rapidly responding indicator than ESR

• Increases first and fastest

• Usually returns to normal quicker

• ↓ when inflammatory process suppressed by anti-inflammatory agents

Elevated

• Acute, noninfectious inflammatory reaction → Rheumatoid arthritis, Reiter syndrome

• Collagen or vascular disease → Vasculitis syndromes, Lupus

• Bacterial infection

• Malignancy

Ferritin

• Can be elevated in conditions not reflecting iron stores

• Elevation occurs 1-2 days after onset of acute illness and level peaks 3-5 days

Units: ng/mL

Elevated

• Juvenile idiopathic rheumatoid arthritis

• Infections

• Lymphoma

• Metastatic disease

schirmer test

tests tear deficiency (how moist is the eye, measures reflex tear production)

Folded sterile filter paper placed over the margin of each lower eyelid (At the junction of the middle and lateral thirds)

→ Patient gently closes eyes and waits 5 minutes

→ Wetting of < 5mm is indicative of aqueous tear deficiency

Positive can help diagnose Sjogrens syndrome

age is limitation (older → drier)

salivary flow study

measures saliva production rate

Patient asked to expectorate once and then collect all saliva into a pre-weighed container

→ After 5-15 minutes, collection vial re-weighed

→ Volume of saliva is calculated

→ Collection of ≤ 0.1mL/min is indicative of abnormal salivary function

Postive can help diagnose sjogrens syndrome

age is limitation (older → drier)

Rheumatologic lab testing options

• ESR

• CRP

• Ferritin

• Uric Acid

• HLA-B27

• Rheumatoid Factor

• ANA

• AnH-CCP anHbodies

• ANCA : Antineutrophil Cytoplasmic Antibody

• Antiphospholipid Antibodies : Anticyclic-Citrullinated peptide antibodies

Uric Acid

A serum test that evaluates the level of uric acid in the blood

Units: mg/dL

Elevated (Hyperuricemia)

• Gout

• Serum urate > 6.8mg/dL = Diagnostic

• Above this^^, threshold crystals may deposit in joints and soft tissue

• Therapeutic target range < 6.0mg/dL

Diagnostic serum urate level for gout

> 6.8 mg/dL

Above this, crystals may deposit in joints/tissues

therapeutic target range for serum urate after gout

< 6.0 mg/dL

Human Lymphocyte Antigen (HLA-B27)

A serum test for specific antigens that is associated with certain autoimmune diseases. Should be negative.

Positive: may indicate ankylosing spondylitis (MC), reiter syndrome, anterior uveitis, graves disease

Rheumatoid Factor (RF)

A serum test used in the diagnosis of rheumatoid arthritis, poor specificity.

Units: units/mL

Rheumatoid arthritis: 26-90%

Sjögrens syndrome: 75-95%

Mixed connective tissue disease: 50-60%

Systemic lupus erythematous: 15-35%

Polymyositis or Dermatomyositis: 5-10%

Non rheumatic disease: varies

Anti-CCP Antibodies

Anticyclic-Citrullinated peptide antibodies

Antibodies that indicate rheumatoid arthritis, especially when RF is negative and pt has unexplained joint inflammation.

units: units/mL

Elevated = rheumatoid arthritis 

Patients with early RA (30-40%) may have a normal Anti-CCP

associate antiCCP with ___

rheumatoid arthritis

Antineutrophil Cytoplasmic Antibody (ANCA)

Antibodies directed against cytoplasmic components of neutrophils

Detected via immunofluorescence staining

2 main patterns: 

• P-ANCA

• C-ANCA → 95-99% specific for Wegeners granulamatosis

Indications

• Evaluate for Wegener Granulomatosis

• Follow course of disease

• Monitor response to therapy

Antinuclear Antibody (ANA)

A group of proteins that react against cellular nuclear material, used to diagnose autoimmune diseases.

Reported as dilution, negative at 1:40

Sensitive but not specific

Indications: suspect autoimmune disease

Positive test: Must perform additional antibody testing to corroborate diagnosis

False negative can occur is pt is on steroids

ANA disease percentages

Systemic lupus erythematosus: 95%

Progressive systemic sclerosis (Scleroderma): 70%

Sjögren syndrome: 60%

Rheumatoid arthritis: 30%

Dermatomyositis: 30%

Polyarteritis: 10%

syphilis

causes false positive antiphospholipid antibodies

ANA patterns

Homogenous : Lupus

Peripheral : Lupus

Speckled

• Lupus

• Scleroderma

• RA

• Mixed connective tissue

• Sjogren

• Polymyositis

Nucleolar : Scleroderma or Polymyositis

ANA subtypes

• Anti-Smith, AnH-RNP, AnH-Jo

• Anti-ssA(Ro) and AnH-ssB(La)

• Anti-Mi-2

• Anti-scleroderma-70

• Anticentromere

• Anti-Double strand DNA

Anti-Smith, Anti-RNP, Anti-Jo Antibodies

Anti-extractable Nuclear Antigens

Indications

• Assist in diagnosis of SLE and MCTD

• Eliminate other rheumatoid diseases

Results

• Anti-Smith → + 30% pts with SLE

• Anti-RNP → + nearly 100% pts with MCTD

• Anti-Jo → + in autoimmune myositis (polymyositis & dermatomyositis)

Anti-ss A(Ro) and Anti-ss B(La) Antibodies

Anti-extractable nuclear antigens

Indications : Diagnose Sjögrens Syndrome

Produce a speckled immunofluorescent pattern

Anti-ss A(Ro) : 60-70% pts with primary Sjögrens Syndrome

Anti-ss B(La) : 50-60% pts with primary Sjögrens Syndrome

Anti-Mi-2 Antibodies

Produce a speckled ANA staining pattern

Positive

• Dermatomyositis : Typically a more severe form, Increased muscle weakness

Antiphospholipid Antibodies

Antibodies that can indicate antiphospholipid syndrome, associated with thrombotic events.

Subtypes

• Anticardiolipin antibodies

• Anti-beta-2 Glycoprotein 1 antibodies

• Lupus anticoagulant assay

Indications

• 1 or more unexplained venous or arterial thrombotic events

• 1 or more unexplained adverse outcomes in pregnancy

• Patients with lupus

Positive antibodies

• Antiphospholipid antibody syndrome

• Lupus at risk

Interfering Factor: Patients who have or had syphilis will have false positive results

Anti-scleroderma-70 Antibodies

Normal = negative

Reported as titer/dilution

Indications

• Suspect Scleroderma

• Monitor therapy effectiveness

Results

• + in 45% of patients with Scleroderma

• Higher titer more likely scleroderma exists and more active disease

• As disease responds to treatment titer should decrease

anticentromere antibodies

Normal = negative

Reported as a dilution above screening titer

Indications

• Concern for CREST syndrome (a Variant of scleroderma)

No correlation between titer and severity of disease

Anti-double strand DNA Antibodies

units: IU/mL

Indications : Diagnosis and follow up of SLE

Results

• Elevated in pts with active Lupus 65-80%

• Titer should ↓ with successful therapy

• Titer should ↑ with exacerbation of SLE

Review table