Clinical and demographic characteristics of TTP and TTP-like syndrome
As demonstrated in Table 1, during the study period, 78 adults presenting with the first episode of suspected TTP were compliant with the inclusion criteria and were analyzed for the study’s endpoints. The diagnostic median age was 45 years (IQR: 30–62), and females occupied the majority of the patients(53.85%). The median age of patients in the TTP group was 46 years(IQR 36-68), and that for the TTP-like syndrome group was 40 (26-64). A total of 12 patients (48.00%) in the TTP group and 30 patients (56.60%) in the TTP-like syndrome group were female. There were no differences in demographic characteristics between the two groups.
In addition, the PLASMIC score of the TTP-like syndrome group was notably lower than that of TTP group[4 (IQR 3, 4) vs. 4 (IQR 4, 5), P=0.006]. In terms of treatment, PE was used in 30 cases (38.46%), plasma infusion in 44 cases(56.41%), glucocorticoids in 57 cases(73.08%), and immunoglobulin in 38 cases (48.72%). A total of 16 (20.51%) patients received rituximab therapy, and 19 (24.36%) patients received other immunosuppressive therapies. Moreover, only two patients were treated with continuous renal replacement therapy (CRRT). In the TTP group, the proportions of patients who received PE (72.00% ) and glucocorticoids (88.00%) were more than those in the TTP-like syndrome group (66.04% and 22.64%, P<0.001), respectively. In addition, the plasma infusion was significantly lower in the TTP group compared to the TTP-like syndrome group (40.00% vs. 64.15%, P<0.001).
In patients with VMTD, the common etiologies included autoimmune diseases (26 cases, 33.33%), hematopoietic stem cell transplantation (HSCT, 17 cases, 21.79%), pathogen (8 cases, 10.60%), pregnancy (7 cases, 8.97%), malignant hypertension (7 cases, 8.97%), malignancy (6 cases, 7.69%), cobalamin C defect (3 cases, 3.85%), and polytrauma (1 case, 1.28%). Different from the TTP-like syndrome group, the etiologies of TTP do not appear in pregnancy, cobalamin C defect, polytrauma, and malignant hypertension. As Figure 2 illustrated, the proportion of patients in the TTP group was more remarkable in autoimmune disease than that of the TTP-like syndrome group (64.00% vs. 18.87%, P<0.001). There was no difference in the other four etiologies between the two groups.
Compared to patients in the TTP group, those who were among the TTP-like syndrome group were more likely to have higher NLR [9.33 µg/mL (IQR 5.24, 16.46) vs. 3.91 (IQR 2.55, 5.87), P=0.025] and more inclined to have lower ALB [32 g/L (IQR 28, 36) vs. 38 g/L (IQR 33, 42), P=0.002]. Otherwise, there were no differences in WBC count (P=0.248) or the level of FIB (P=0.645) and D-dimer (P=0.284) between the two groups. No difference in RDW (P=0.120) was observed between the two groups, either (Figure 3).
Target organ damage ( TOD) caused by circulating microthrombosis
The spectrum of TOD for each group was recorded in Figure 4. Although the prevalence of acute hepatic injury (AHI), acute myocardial injury (AMI), and acute pancreatitis (AP) were higher and acute kidney injury (AKI) was lower in the TTP-like syndrome group patients, the differences were found insignificant. There was a notable difference in central nervous system dysfunction(CNSD, 33.96% vs. 76.00%, P<0.001) between the two groups.
Laboratory parameters in hematologic features
The results of laboratory tests in TTP group and TTP-like syndrome group were very different (Table 2). The higher median levels of schistocytes [3.0% (IQR 1.0, 5.0) vs. 0.8% (IQR 0.4, 2.0), P<0.001], Ret [0.167*106/μL (IQR 0.124, 0.234) vs. 0.074 *106/μL (IQR 0.032, 0.127), P<0.001], TBIL [61.6 μmol/L (IQR 29.7, 122.5) vs. 32.0 μmol/L (IQR 19.85, 69.0), P=0.002], IBIL [42.8 μmol/L (IQR 20.4, 89.3) vs. 15.1 μmol/L (IQR 9.3, 25.7), P<0.001], LDH [1150 U/mL (IQR 505, 1949) vs. 498 U/mL (IQR 317, 1135), P=0.007], and CFH [125 mg/L (IQR 88, 356) vs. 38 mg/L (IQR 23, 90), P<0.001] were evidenced among TTP group. Furthermore, TTP group showed a lower median level of Plt [8*109/μL (IQR 5, 20) vs. 27*109/μL (IQR 12, 53), P<0.001], haptoglobin [5.83 mg/dL (IQR 5.83, 19.90) vs. 5.83 mg/dL (IQR 5.83, 59.20), P=0.044], and ADAMTS13 activity [5.0% (IQR 0.0, 6.8) vs. 43.3% (IQR 31.2, 48.5), P<0.001] than TTP-like syndrome group.
After the follow-up, the outcome of 21 (26.92%) patients was clinical death. Kaplan-Meier analysis was used to analyze the survival probability of VMTD patients in the two groups, so as to determine their prognoses(Figure 5). Survival analysis revealed a relatively lower cumulative survival rate in the TTP group than in the TTP-like syndrome group (log-rank test: X2 =5.368, P=0.021).