Background Liquid plasma (LP) is a never-frozen product stored at 1-6 °C with a shelf-life of 21–26 days and is often used as a bridge in emergency transfusions. Our previous data show that expanding LP use in surgical and routine transfusions does not compromise clinical outcomes and effectively reduces product wastage. However, the stability of ADAMTS13 activity in LP and its clinical implication in the management of immune-mediated thrombotic thrombocytopenic purpura (iTTP) remain unexplored.

Objective To evaluate the stability of ADAMTS13 activity and global clotting function in LP throughout its shelf-life and to assess the safety of LP as an adjunct to thawed plasma (TP) in therapeutic plasma exchange (TPE) for patients with acute iTTP.

Methods Ten units of LP from distinct whole blood donations were collected on day 27. Ten units of TP from frozen plasma within 24 hours on day 6 served as the control. Three units of LP collected within 5 days of whole blood donation were serially sampled at multiple time points through day 26, with the initial collection designated as day 0. All samples were stored at -80°C and later tested in batch. ADAMTS13 activity was quantified using a clinical ELISA-based assay, and the global coagulant activity was assessed using a thrombin generation assay (trigged by 0.2 pM tissue factor in the presence of 4 µM PCPS). Moreover, a retrospective review identified adults with iTTP treated in our institute between June 15, 2015, and June 1, 2024. Patients treated with a combination of TP and LP were compared with those treated with TP alone. Statistical comparisons were made using Student's t-test for continuous variables and Fisher's exact test or multivariate regression for categorical variables. A p-value <0.05 was considered statistically significant.

Results The mean level of ADAMTS13 activity in LP was (0.98 ± 0.14) IU/mL with a median of 0.989 IU/mL (range: 0.94 -1.01 IU/mL), comparable to that of TP (1.02 ± 0.13) IU/mL; median 1.04 IU/mL; range: 0.65 to 1.21 IU/mL) with a p-value of 0.277 on day 1 post-expiration. Serial testing of LP units revealed sustained ADAMTS13 activity and stable peak thrombin generation over the 26-day observation period. Clinically, 20 patients with acute iTTP were identified. Ten patients with 14 acute episodes of iTTP received a combination of TP and LP, with LP comprising 8.3-55% of the plasma replacement volume. The remaining 10 patients were treated with TP alone. All patients received corticosteroids and rituximab; 8 patients in the LP group also received caplacizumab. No differences in adverse outcomes including coagulopathy and mortality were observed between the two groups (p>0.05).

Conclusion Liquid plasma preserves stable ADAMTS13 activity and global coagulation function throughout its shelf-life. Its adjunct use in TPE for iTTP was not associated with increased bleeding and mortality. These findings support the safety and effectiveness of LP as a complementary option to TP in the management of iTTP, offering greater flexibility in emergent care and contributing to reduced product waste.

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2025
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