Anti SCL - 70 AntiBody by EIA

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Report in 120Hrs

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No Fasting Required

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Autoantibody against topoisomerase I.

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Anti SCL-70 Antibody by EIA - Comprehensive Medical Test Guide

Section 1: Why is it done?
- Test Overview: The Anti SCL-70 antibody test (also known as anti-topoisomerase I antibody) detects autoantibodies directed against the nuclear protein topoisomerase I, a key antigen in systemic sclerosis (scleroderma).
- Primary Indications for Testing:
  - Suspicion of diffuse cutaneous systemic sclerosis (dcSSc) or limited cutaneous systemic sclerosis (lcSSc)
  - Investigation of Raynaud's phenomenon with suspected systemic sclerosis
  - Evaluation of progressive skin thickening and fibrosis
  - Assessment of pulmonary fibrosis associated with autoimmune connective tissue disease
  - Support for diagnosis of scleroderma-related autoimmune disorders
- Typical Timing and Circumstances:
  - Initial presentation with clinical features suggestive of systemic sclerosis
  - Part of comprehensive autoimmune antibody panel evaluation
  - Monitoring disease progression and determining clinical phenotype
  - Early in disease course when clinical manifestations first appear
Section 2: Normal Range
- Reference Values:
  - Negative/Normal: < 1.0 Index (or < 1.0 EIA Units, depending on laboratory)
  - Borderline/Equivocal: 1.0 - 1.5 Index (laboratory dependent)
  - Positive: > 1.5 Index (or > 1.0 EIA Units for some laboratories)
- Units of Measurement:
  - EIA Index (Enzyme Immunoassay Index) - most common reporting unit
  - EIA Units (U/mL) - alternative reporting method
  - Reference ranges vary by laboratory and assay platform used
- Interpretation Guide:
  - Negative Result: Indicates absence of anti-topoisomerase I antibodies; does not exclude systemic sclerosis, as other antibodies (anti-centromere, anti-RNA polymerase III) may be present
  - Positive Result: Highly specific for diffuse cutaneous systemic sclerosis; strongly associated with early-stage disease and pulmonary fibrosis complications
  - Borderline Result: May warrant repeat testing or clinical correlation; consider laboratory-specific cut-off values
Section 3: Interpretation
- Clinical Significance of Results:
  - Positive Anti-SCL-70: Present in approximately 25-30% of systemic sclerosis patients; highly specific marker with 95%+ specificity for SSc diagnosis; almost never found in healthy individuals
  - Association with Disease Phenotype: Strongly associated with diffuse cutaneous systemic sclerosis (dcSSc), characterized by widespread skin fibrosis; linked to increased risk of pulmonary fibrosis and interstitial lung disease (ILD); associated with worse prognosis compared to anti-centromere positive patients
  - Negative Anti-SCL-70: Does not exclude systemic sclerosis diagnosis; other SSc-specific antibodies may be present (anti-centromere in 50-60% of lcSSc, anti-RNA polymerase III in 4-29% of dcSSc)
- Factors Affecting Results and Interpretation:
  - Disease duration: Antibodies usually present early in disease course; may persist or change titers over time
  - Immunosuppressive therapy: May not affect antibody positivity; treatment response monitored through clinical parameters rather than antibody titers
  - Laboratory variation: Different EIA platforms may yield slightly different cutoff values and reference ranges
  - Age and sex: No significant age or sex differences in antibody prevalence among SSc patients
  - Genetic predisposition: No single gene determines antibody presence; polygenic inheritance with HLA association
- Prognostic Implications:
  - Positive anti-SCL-70 predicts diffuse skin involvement and earlier onset of pulmonary complications
  - Higher risk of rapid progression of interstitial lung disease requiring close respiratory monitoring
  - Associated with more severe renal crisis compared to other SSc antibody subtypes
Section 4: Associated Organs
- Primary Organ Systems Involved:
  - Integumentary System (Skin): Primary target; fibrosis and thickening of dermis and subcutaneous tissue
  - Respiratory System (Lungs): Most commonly affected internal organ; pulmonary fibrosis/interstitial lung disease (ILD) develops in 40-90% of anti-SCL-70 positive patients
  - Cardiovascular System: Myocardial fibrosis, conduction abnormalities, pulmonary hypertension secondary to lung disease
  - Renal System: Scleroderma renal crisis (SRC) with acute glomerulonephritis; increased risk in anti-SCL-70 positive patients
  - Gastrointestinal System: Smooth muscle atrophy and fibrosis; dysphagia, reflux, esophageal dysmotility
- Diseases and Conditions Associated with Anti-SCL-70 Positivity:
  - Systemic Sclerosis (Scleroderma): Primary disease; marker of diffuse cutaneous subtype with severe organ involvement
  - Pulmonary Fibrosis: Progressive lung disease; restrictive pattern on pulmonary function tests; risk of respiratory failure
  - Scleroderma Renal Crisis (SRC): Hypertensive emergency with acute kidney injury; higher prevalence in anti-SCL-70 positive patients
  - Secondary Pulmonary Hypertension: From progressive ILD or direct vascular involvement
  - Myositis: Overlapping syndrome with muscle inflammation; may occur with anti-SCL-70 and anti-myositis antibodies
- Potential Complications and Risks:
  - Progressive dyspnea and respiratory insufficiency requiring oxygen therapy or mechanical ventilation
  - Acute kidney injury with end-stage renal disease requiring dialysis
  - Digital ulceration and gangrene from severe vascular involvement and contractures
  - Malabsorption and severe malnutrition from GI involvement
  - Cardiac arrhythmias and congestive heart failure from myocardial involvement
  - Disability and loss of functional capacity from severe skin fibrosis and joint involvement
Section 5: Follow-up Tests
- Confirmatory and Complementary Autoimmune Testing:
  - Antinuclear Antibody (ANA) Panel: Initial screening test; usually positive in SSc patients; helps confirm systemic autoimmune disease
  - Anti-Centromere Antibody (ACA): Mutually exclusive with anti-SCL-70 in most cases; positive in limited cutaneous disease; associated with better prognosis and lower ILD risk
  - Anti-RNA Polymerase III (RNAP III) Antibody: Associated with diffuse disease and high risk of scleroderma renal crisis; usually mutually exclusive with anti-SCL-70
  - Anti-PM/Scl Antibody: May occur with anti-SCL-70 in overlap syndrome; indicates scleromyositis
- Pulmonary Assessment Tests:
  - High-Resolution Computed Tomography (HRCT) of Chest: Gold standard for detecting pulmonary fibrosis; baseline imaging essential in anti-SCL-70 positive patients; repeated periodically to monitor disease progression
  - Pulmonary Function Tests (PFT): Forced vital capacity (FVC) and diffusion capacity (DLCO); performed at baseline and every 6-12 months; detects progressive restrictive disease
  - 6-Minute Walk Test (6MWT): Assesses functional exercise capacity; oxygen desaturation during testing indicates disease progression
  - Echocardiography: Screen for pulmonary hypertension and cardiac dysfunction; assess right ventricular function
- Renal Function Monitoring:
  - Serum Creatinine and Blood Pressure: Monitor at every visit; sudden elevation suggests scleroderma renal crisis
  - Urinalysis: Screen for proteinuria and hematuria; monthly or quarterly surveillance recommended
  - Estimated Glomerular Filtration Rate (eGFR): Calculate regularly to assess renal function decline
- Additional Diagnostic Tests:
  - Complete Blood Count (CBC): Monitor for anemia and treatment-related cytopenias
  - Comprehensive Metabolic Panel (CMP): Assess electrolytes, liver function, and renal status
  - Skin Biopsy: May be performed for histological confirmation if diagnosis unclear; shows dermal fibrosis and collagen deposition
  - Muscle Enzymes (CPK, Aldolase): If myositis suspected; usually normal in pure SSc
- Monitoring Frequency and Schedule:
  - Early Disease (first 2-3 years): Frequent monitoring (every 3-6 months); baseline imaging and comprehensive labs essential
  - Established Disease: Every 6-12 months or as clinically indicated; adjust frequency based on disease activity
  - PFTs and HRCT: Annually at minimum; more frequently if FVC declining or symptoms worsening
Section 6: Fasting Required?
- Fasting Requirement:
  - Fasting Required: NO
- Explanation:
  - The Anti SCL-70 antibody test by EIA (Enzyme Immunoassay) is a serum-based antibody detection assay that does not require fasting. Food and fluid intake do not affect the detection of circulating autoantibodies.
  - Patients may eat and drink normally before the test without affecting results.
- Medications:
  - Medications to Continue: All routine medications should be taken as prescribed. Immunosuppressive therapy, corticosteroids, and other treatments do not interfere with antibody detection.
  - Medications to Avoid: None specifically; no medications need to be held before this test
- Additional Patient Preparation and Instructions:
  - Timing: Blood draw can be performed at any time of day; no time-of-day restrictions apply
  - Hydration: Patient should be well-hydrated before phlebotomy; adequate fluid intake helps with blood draw ease
  - Physical State: No specific physical activity restrictions; patient should avoid strenuous exercise immediately before blood draw if possible
  - Sample Collection: Standard venipuncture using serum separator tube; 5-7 mL of blood typically required
  - Documentation: Inform healthcare provider of recent infections or vaccinations as these may transiently affect some immune markers (though anti-SCL-70 typically remains stable)
  - Appointment Scheduling: Test can be scheduled at the patient's convenience; no need to arrange special timing

How our test process works!