LABORATORY DIAGNOSTIC Flashcards
Was sind die Screening-Tests für Entzündungen?
Screening tests for inflammation include C-reactive protein (CRP; most rapid onset), erythrocyte sedimentation rate (ESR), and serum protein electrophoresis (SPEP; most inclusive).
Ist ein positiver ANA-Test diagnostisch für SLE?
A positive antinuclear antibody (ANA) is not diagnostic of systemic lupus erythematosus (SLE) and can be found in normal individuals and in patients with various other autoimmune and inflammatory diseases.
Wie unterscheiden sich RF und anti-CCP bei rheumatoider Arthritis?
Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibodies are equally sensitive in rheumatoid arthritis (RA) patients, but anti-CCP is more specific.
Was deutet ein positiver ANCA-Test mit PR3- oder MPO-Spezifität an?
A positive anti-neutrophil cytoplasmic antibodies (ANCA) test with anti-proteinase3 (PR3) or anti-myeloperoxidase (MPO) specificity supports the clinical diagnosis of a systemic necrotizing vasculitis.
Was deuten niedrige Komplementwerte (C3, C4) an?
Low complement (C3, C4) levels suggest an immune complex-mediated disease, whereas undetectable CH50 activity may indicate a disease associated with a hereditary complement component deficiency.
Was ist die ESR und wie wird sie gemessen?
The Westergren ESR is the gold standard and is a measurement of the distance in millimeters that red blood cells (RBCs) fall within a specified tube over 1 hour. ESR is an indirect measurement of inflammation based upon alterations in acute-phase reactants and quantitative immunoglobulins.
Was sind Akute-Phase-Proteine?
Acute-phase reactants are a heterogeneous group of proteins (fibrinogen, haptoglobin, CRP, serum amyloid A, ferritin, alpha-1-antitrypsin, and others) synthesized in the liver as part of the acute inflammatory response.
Welche Faktoren beeinflussen die ESR?
Any condition that causes either a rise in the concentration of acute-phase reactants or hypergammaglobulinemia (polyclonal or monoclonal) will cause an elevation of the ESR.
Was sind die Ursachen für eine extrem hohe oder niedrige ESR?
Markedly elevated ESR (>100 mm/hour): Infection, bacterial (35%), Connective tissue disease (25%), Malignancy (15%), Other causes (25%). Markedly low ESR (0 mm/hour): Affibrinogenemia/dysfibrinogenemia, Agammaglobulinemia, Extreme polycythemia.
Ist die manuelle Westergren-Methode die häufigste Technik zur ESR-Messung?
No. Surveys reveal that roughly two-thirds of laboratories across the globe use either modified automated measurements based on the Westergren method or alternative novel methods.
Wie wird eine erhöhte ESR evaluiert?
Complete history and physical examination. Check SPEP, fibrinogen, and CRP. Recheck the ESR in 1–3 months if no explanation is found.
Was ist CRP und wie wird es gemessen?
CRP is a pentameric protein composed of five identical, noncovalently-linked, 23-kD subunits. It is measured by immunoassay or nephelometry.
Wann sollte CRP statt ESR gemessen werden?
The CRP test may be preferred in situations where monitoring early response to therapy is desired, when factors influencing the ESR specifically are present, or when there are discordant results for the ESR and CRP.
Wie verändert sich die SPEP bei Entzündungen?
The typical pattern on SPEP for the inflammatory response includes increases in the α-2 zone most prominently, gamma zone, α-1 zone, and the β-y area. Negative acute-phase reactants are seen as a diminished albumin peak.
Was ist Procalcitonin (PCT) und wie wird es interpretiert?
PCT is a propeptide of calcitonin. In bacterial infections, PCT levels are significantly elevated. Values ≥ 0.5 ng/mL retain a high specificity for bacterial infection.
Wie werden ANAs gemessen?
The preferred method is the indirect immunofluorescence (IIF) technique using human epithelial type 2 (HEp-2) cells as substrate.
Was ist eine LE-Zelle?
An LE cell is a neutrophil that has engulfed the intact nucleus of another cell. It represents the end result of ANAs binding to a nucleus and fixing complement resulting in phagocytosis by a neutrophil.
Wann gilt ein ANA-Test als positiv?
A positive ANA is arbitrarily defined as that level of ANAs that exceeds the level seen in 95% of the normal population. Clinically significant titers are usually ≥1:160.
Kann ein gesunder Mensch einen positiven ANA haben?
Yes. The frequency depends on ANA titer: ANA 1:40: 20%–30% of healthy individuals, ANA 1:80: 10%–15%, ANA 1:160: 5%, ANA 1:320: 3%.
Kann ein SLE-Patient ANA-negativ sein?
Yes, but very rarely. Few patients (<1%) with active, untreated SLE will have a negative ANA.
Welche Erkrankungen sind mit einem positiven ANA assoziiert?
Siehe Tabelle 6.1 (wird als separate Karte erfasst).
Kann der ANA-Titer zur Verlaufskontrolle bei SLE genutzt werden?
No. There is no evidence that variations in ANA titer (level) as measured by the screening ANA correlate with disease activity.
Welche Bedeutung hat das ANA-Fluoreszenzmuster?
Certain patterns of fluorescence are associated with specific nuclear antigens and diseases (Table 6.2). Homogenous: SLE; Speckled: SS-A/SS-B; Nucleolar: systemische Sklerose.
Ist ANA ein guter Screening-Test für SLE?
No. Screening the entire population for ANA would result in many more false positives than true SLE cases. Clinical suspicion is key.
