Prevalence of heparin in samples submitted for lupus anticoagulant testing

Management of the thrombotic risk associated with COVID-19: guidance for the hemostasis laboratory

Coronavirus disease 2019 (COVID-19) is associated with extreme inflammatory response, disordered hemostasis and high thrombotic risk. A high incidence of thromboembolic events has been reported despite thromboprophylaxis, raising the question of a more effective anticoagulation. First-line hemostasis tests such as activated partial thromboplastin time, prothrombin time, fibrinogen and D-dimers are proposed for assessing thrombotic risk and monitoring hemostasis, but are vulnerable to many drawbacks affecting their reliability and clinical relevance. Specialized hemostasis-related tests (soluble fibrin complexes, tests assessing fibrinolytic capacity, viscoelastic tests, thrombin generation) may have an interest to assess the thrombotic risk associated with COVID-19. Another challenge for the hemostasis laboratory is the monitoring of heparin treatment, especially unfractionated heparin in the setting of an extreme inflammatory response. This review aimed at evaluating the role of hemostasis tests in the management of COVID-19 and discussing their main limitations.

The effect of unfractionated heparin, enoxaparin, and danaparoid on lupus anticoagulant testing: Can activated carbon eliminate false-positive results?

BACKGROUND

Heparins and heparinoids interfere with functional clotting assays used for lupus anticoagulant (LAC) detection. However, current guidelines for LAC testing do not provide clear guidance on this matter.

OBJECTIVES

We aimed to assess to effect of unfractionated heparin (UFH), enoxaparin, and danaparoid on LAC assays over broad anti-Xa activity ranges and to evaluate whether activated carbon (AC) is able to neutralize these effects.

METHODS

UFH (0.1-3.0 IU/mL), enoxaparin (0.2-2.9 IU/mL), and danaparoid (0.6-2.2 IU/mL) were spiked to normal pooled plasma. AC was added at multiple activity levels. Anti-Xa assays and LAC tests were performed on all samples using Stago analyzers and reagents.

RESULTS

Abnormal activated partial thromboplastin time (APTT) screening and mixing tests were obtained at the lowest levels for all compounds. Abnormal APTT confirmation tests were seen from 2.5 and 1.9 anti-Xa IU/mL for enoxaparin and danaparoid, respectively. Abnormal dilute Russell's viper venom test (dRVVT) screening tests were obtained from 1.6, 1.4, and 1.1 anti-Xa IU/mL for UFH, enoxaparin, and danaparoid, respectively. Mixing tests were abnormal from 2.5 and 1.3 anti-Xa IU/mL for enoxaparin and danaparoid, respectively. Abnormal dRVVT confirmation results were seen for danaparoid only from 1.9 anti-Xa IU/mL. AC was unable to neutralize anti-Xa activity in plasma and overcome the effect of the tested anticoagulants on LAC assays but may cause prolongation of APTT clotting times.

CONCLUSIONS

UFH, enoxaparin, and danaparoid clearly affected LA tests; however, false-positive LAC conclusions were obtained at supratherapeutic enoxaparin and danaparoid levels only. AC may prolong APTT screen clotting times, requiring 3-step testing to avoid potential misdiagnosis of LAC.

Current practices for lupus anticoagulant testing at a tertiary care hospital and impact on laboratory resources

BACKGROUND AND OBJECTIVES

The lupus anticoagulant (LA) test is an advanced test that is time consuming and requires a highly trained lab specialist. A high proportion of clinicians do not adhere to international guidelines and request the test inappropriately.

DESIGN AND SETTINGS

This descriptive study covered the period from January 2012 and January 2013 at the Hematology Laboratory at King Khalid University Hospital, Riyadh.

PATIENTS AND METHODS

The 274 lupus anticoagulant requests were categorized as proper or improper based on the guidelines of the International Society of Thrombosis and Haemostasis (ISTH). Data on numbers of requests and cost are summarized.

RESULTS

Of the 274 requests, 222 (81%) were classified as proper while 52 (19%) requests did not satisfy ISTH guidelines. The most frequently encountered incorrect indications were warfarin therapy (46%), heparin therapy (27%), a normal aPTT with no clinical indication (25%) and low serum fibrinogen levels (2%). The total cost of all improper requests was about 41080 SAR (10954 USD).

CONCLUSION

A majority of improper requests were related to anticoagulant therapy, which highlights the importance of implementing a comprehensive diagnostic algorithm for patients on warfarin and heparin therapy.