Pregnant patients are particularly vulnerable to misdiagnosis of TTP in the ED. One 2009 study of four tertiary hospitals found that emergency physicians often misdiagnosed this presentation in pregnant women as “panic attack, domestic violence, or gastroenteritis.”⁵ Pregnant women comprise up to seven percent of TTP/Hemolytic Uremic Syndrome (HUS) patients. When thrombocytopenia is found in pregnant patients, clinicians should have a high degree of suspicion for TTP in addition to HELLP Syndrome, eclampsia, and HUS.⁵

Testing for TTP should include a CBC, CMP, blood smear, coagulation panel, fibrinogen, D-Dimer, LDH, troponin, HIV PCR, urinalysis, Coomb’s testing and ECG.⁴ ADAMTS13 level can be considered to assist the inpatient team. In TTP, Coomb’s testing will be negative, and the coagulation panel will typically not be significantly deranged. In the long term, the mechanism of ADAMTS13 deficiency should be determined—whether due to inhibitory or non-inhibitory autoantibodies, or due to the hereditary form of the disease. The labs that assess this, such as the FRETS-VWF73-based assay, take several days to result and are best pursued in an inpatient setting.⁷ Given the prolonged time that these labs may take to result, clinicians may consider using the PLASMIC score to aid in predicting the likelihood of TTP. One point is given for platelet count less than 30,0000, presence of hemolysis, mean corpuscular volume less than 90 fL, INR less than 1.5, creatinine less than 2.0 mg/dL, absence of cancer, and the absence of solid organ or stem cell transplant. A PLASMIC score higher than 5 suggests a high probability of TTP, with a sensitivity of approximately 99 percent and a specificity of 57 percent.⁶

Management

TTP’s mortality ranges from 4 to 31 percent, but the disease is associated with multiple comorbidities, including hypertension, major depressive disorder, and cognitive abnormalities. Thus, early management is essential for patient outcomes.⁴ Early hematology consultation should be obtained when TTP is suspected.

Therapeutic plasma exchange (TPE) with fresh frozen plasma (FFP) is the first-line treatment, by simultaneously supplying fresh ADAMTS13 and removing anti-ADAMTS13 autoantibodies. Delays in this treatment are directly correlated with increases in patient mortality.¹ The International Society of Thrombosis and Haemostasis also recommends corticosteroids in addition to TPE, given their possible mortality benefit.⁷ High dose pulse steroids, such as methylprednisolone 10 mg/kg/day for 3 days, or an oral prednisone taper may be used.¹ Rituximab may be given as well, largely due to prevention of relapse.⁷ Caplacizumab, a new medication that targets the A1 domain of VWF and prevents platelet aggregation has shown remarkable efficacy in improving clinical outcomes and reducing patient mortality and risk of relapse.^7,8 Much like TPE and steroids, earlier treatment with caplacizumab is associated with improved patient outcomes.⁸