Cedars-Sinai Medical Center

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A BI-WEEKLY PUBLICATION FROM THE CEDARS-SINAI CHIEF OF STAFF May 9, 2014 | Archived Issues

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CME Newsletter - May 2014


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Lupus, Antiphospholipid Work-Ups Offered

Two new panels available at Cedars-Sinai integrate the current International Society for Thrombosis and Hemostasis consensus criteria for evaluation of lupus anticoagulant (L.A.) and antiphospholipid syndrome.

Lupus Anticoagulant Panel (2 light blue top tubes)

Indication: Exploration of an unexplained prolonged aPTT in a patient who is not bleeding

Includes:

  • Screening dRVVT
  • Screening PTT-LA
  • Thrombin time
  • PT
  • Interpretation

Reflex testing (if indicated): dRVVT mixing study; confirmatory dRVVT; PTT-L.A. mixing study; confirmatory Staclot-L.A.*

Methodology: L.A. testing consists of a panel of assays designed to optimize diagnostic potential. Screening steps are performed first for two phospholipid-dependent assays. If the screen is positive in one or both, then mixing steps are performed for the respective assay to assess inhibitor effect; if inhibitor effect is demonstrated, its phospholipid dependence is evaluated in the confirmatory step.

Limitations: L.A.s are heterogenous in terms of antigenic recognition. aPTT reagents are variable in their phospholipid composition. Variability in the ability to detect L.A.s exists between different assays and between different labs. Consequently, no single assay allows detection of all L.A.s.

Interfering substances: Coumadin®, heparin, direct thrombin inhibitors, direct FXa inhibitors

*Note: Staclot-L.A. (also known as L.A. by hexagonal) is a confirmatory assay for L.A. that should only be evaluated when the screening PTT-LA is positive. It is not available to order separately from the Lupus Anticoagulant Panel.

Antiphospholipid Syndrome Panel (2 light blue top tubes, 1 red top tube)

Indication: Suspicion for antiphospholipid syndrome in patients with an elevated aPTT and history of arterial or venous thrombosis and/or recurrent fetal loss; systemic lupus erythematosus

Includes:

  • Lupus Anticoagulant Panel (see above)
  • Anti-cardiolipin IgG, IgM, IgA antibodies
  • Anti-β2GPI IgG, IgM, IgA antibodies
  • Interpretation

Reflex testing (if indicated): dRVVT mixing study; confirmatory dRVVT; PTT-LA mixing study; confirmatory Staclot-L.A.

Methodology: See Lupus Anticoagulant Panel above. An enzyme-linked immunosorbent assay is performed for antiphospholipid (anti-cardiolipin and anti-β2GPI) antibody testing.

Limitations: See Lupus Anticoagulant Panel above. False positive syphilis tests (RPR, VDRL) can occur in patients with anti-cardiolipin antibodies and vice versa.

Interfering substances: See Lupus Anticoagulant Panel above.

Patient Preparation

Anticoagulation therapy will affect L.A. assay results:

  • Coumadin and direct Factor Xa inhibitors severely affect the PT and dRVVT assays.
  • Unfractionated heparin and direct thrombin inhibitors severely affect the aPTT and PTT-LA assays. Most dRVVT reagents contain a neutralizing agent for therapeutic levels of UFH.
  • For reliable L.A. interpretation, samples should not be taken from patients receiving anticoagulation.

Reporting

The quantitative results will be accompanied by an interpretation of assay results. For the three-step L.A. testing, appropriate sequential testing with an interpretive report will follow.