Distinguishing and overlapping laboratory results of thrombotic microangiopathies in HIV infection: Can scoring systems assist?

BACKGROUND: Patients with Human Immunodeficiency Virus (HIV) infection are at risk of thrombotic microangiopathies (TMAs) notably thrombotic thrombocytopenic purpura (TTP) and disseminated intravascular coagulation (DIC). Overlap between laboratory results exists resulting in diagnostic ambiguity. METHODS: Routine laboratory results of 71 patients with HIV‐associated TTP (HIV‐TTP) and 81 with DIC with concomitant HIV infection (HIV‐DIC) admitted between 2015 and 2021 to academic hospitals in Johannesburg, South Africa were retrospectively reviewed. Both the PLASMIC and the International Society of Thrombosis and Haemostasis (ISTH) DIC scores were calculated. RESULTS: Patients with HIV‐TTP had significantly (P < .001) increased schistocytes and features of hemolysis including elevated lactate dehydrogenase (LDH)/upper‐limit‐of‐normal ratio (median of 9 (interquartile range [IQR] 5‐12) vs 3 (IQR 2‐5)) but unexpectedly lower fibrinogen (median 2.8 (IQR 2.2‐3.4) vs 4 g/L (IQR 2.5‐9.2)) and higher D‐dimer (median 4.8 (IQR 2.4‐8.1) vs 3.6 g/L (IQR 1.7‐6.2)) levels vs the HIV‐DIC cohort. Patients with HIV‐DIC were more immunocompromised with frequent secondary infections, higher platelet and hemoglobin levels, more deranged coagulation parameters and less hemolysis. Overlap in scoring systems was however observed. CONCLUSION: The laboratory parameter overlap between HIV‐DIC and HIV‐TTP might reflect a shared pathogenesis including endothelial dysfunction and inflammation and further research is required. Fibrinogen in DIC may be elevated as an acute phase reactant and D‐dimers may reflect the extensive hemostatic activation in HIV‐TTP. Inclusion of additional parameters in TMA scoring systems such the LDH/upper‐limit‐of‐normal ratio, schistocytes count and wider access to ADAMTS‐13 testing may enhance diagnostic accuracy and ensure appropriate utilization of plasma.