Abstract Number: PB0844
Meeting: ISTH 2021 Congress
Background: The two commonest microangiopathies in HIV infected patients in South Africa are acquired thrombotic thrombocytopenic purpura (TTP) and disseminated intravascular coagulation (DIC). The microthrombi in TTP are rich in von Willebrand factor (VWF) and platelets, with those in DIC consisting predominantly of fibrin. The treatment of these two conditions is different and accurate initial diagnosis is essential. Research suggest that D-dimes are not elevated in acquired TTP and together with preserved activated Partial Thermoplastic Time (aPTT) and antithrombin (AT) are useful in distinguishing acquired TTP and DIC in HIV-uninfected patients.
Aims: To determine the diagnostic utility of 3 routine parameters, aPTT, D-dimers and AT, in distinguishing between acquired TTP and DIC in HIV-infected patients.
Methods: This study approval human research ethics committee of the University of the Witwatersrand (M160134). aPTT, D-dimer and AT results of patients with HIV-associated TTP were compared with HIV infected patients with laboratory evidence of overt uncompensated DIC. Results were analysed using STATA and for non-parametric parameters, a Mann-Wilcoxon analysis was performed.
Results: The aPTT, AT levels and platelet count were significantly different between HIV-infected patients with DIC compared with HIV acquired TTP (p-values <0.0001). D-dimer levels in HIV-infected patients with TTP were, however, substantially elevated and were not statistically different from HIV infected patients with DIC.
DIC, disseminated intravascular coagulation; TTP, thrombotic thrombocytopenic purpura; aPTT, activated Partial Thromboplastin Time. (Dots above Boxplots represent outlier results).
Figure 1: Boxplots – HIV-infected patients with DIC or acquired TTP : Paired tests for aPTT, D-dimers, antithrombin and platelet count (n=53).
Table 1: Two-sample Wilcoxon rank-sum (Mann-Whitney) test: DIC vs TTP:
|Parameter (normal reference range)||aPTT (31-48 seconds)||D-dimer (0-0.25 mg/L)||Antithrombin (80-120 IU/dL)||Platelets (186-454×109/L)|
|Conclusion:||Significantly prolonged in DIC compared to TTP||No significant difference between DIC and TTP||Significantly reduced in DIC compared with TTP||Significantly reduced in TTP compared with DIC|
Conclusions: The elevated D-dimer levels in HIV infected patients with acquired-TTP probably reflects inflammation and local activation of the coagulation system related to endothelial damage. D-dimer levels are therefore not useful in distinguishing between acquired TTP and DIC in HIV-infected patients.
To cite this abstract in AMA style:Louw S, Mayne A, Mayne ES. Loss of Diagnostic Utility of D-dimers in Secondary Thrombotic Thrombocytopenic Purpura (TTP) in Patients with Human Immunodeficiency Virus (HIV) Infection [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/loss-of-diagnostic-utility-of-d-dimers-in-secondary-thrombotic-thrombocytopenic-purpura-ttp-in-patients-with-human-immunodeficiency-virus-hiv-infection/. Accessed November 29, 2021.
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