Platelet Count Acted as Predictor of Relapse in TTP

Platelet count was found to be a predictor of relapse in thrombotic thrombocytopenic purpura (TTP), according to a study published in the International Journal of Hematology-Oncology and Stem Cell Research. The 3-year relapse and mortality rates of 23.6% and 26.3% were predicated on this platelet count.

TTP is a hematologic disorder that affects more women than men overall and often in adulthood. ADAMTS13 is the lone biomarker to help diagnose TTP in patients. Plasma replacement is regarded as the best treatment for TTP. Although there are more therapeutic approaches to treat TTP, the mortality rate ranges from 10% to 20%.

This study aimed to report the clinical features and outcomes in patients with TTP who were referred to Shariati Hospital in Iran. The study also aimed to assess the rate of relapse and mortality and its associated risk factors.

3D illustration of blood platelet | Image credit: gaetan - stock.adobe.com

All patients who were treated for their first episode of TTP from 2010 to 2017 were considered for the study. Patients with microangiopathic hemolytic anemia (MAHA) and who fulfilled the criteria for TTP through the duration of their hospital visit were included in the study. Patients who had alternative causes for MAHA were excluded. Other patients were excluded after a physical examination. The Bentley score was used as a first clue for deficiency of ADAMTS13, which was assessed during hospitalization and relapses.

Demographic data as well as laboratory tests, treatments, and clinical symptoms were all recorded. Clinical manifestations included fever, jaundice, hematologic presentations, gastrointestinal symptoms, behavior changes, motor or sensory events, and hematuria. Activity level of ADAMTS13, platelet count, hemoglobin, and creatinine were all laboratory manifestations.

All patients were followed up for 3 years for regular visits or relapse. A complete clinical response to treatment was regarded as a sustained platelet count of higher than 150´103/μL with a lactate dehydrogenase lower than 1.5-fold of the upper limit of normal.

There were 114 patients who were included in this analysis. The mean (SD) age of the participants was 39.31 (14.99) years and 80 of the participants were female. First manifestations were mostly commonly hematologic and neurologic symptoms; 37 participants experienced thrombocytopenia, 27 experienced anemia, 15 experienced cerebrovascular accidents, and 9 experienced intracranial hemorrhage.

All patients received corticosteroids of 1mg/kg daily and plasma exchange according to local instructions. A single volume of plasma was exchanged in each session with fresh frozen plasma. This was performed daily until the criteria for tapering the plasma exchange was fulfilled, which included 3 days of normal platelet count or 1 day of higher platelet count. Plasma exchange would then continue every other day.

Median treatment was 11.5 (IQR, 13) days. A total of 21% of patients received pulse corticosteroids and 16.66% received rituximab in addition to the daily plasma exchange and corticosteroids. In total, 75.5% of the patients achieved clinical response, whereas 24.6% developed refractory TTP.

When comparing the patients who took and didn’t take rituximab, there were no differences in clinical response (78.9% vs 75.5%), relapse (26.3% vs 23.33%), and mortality. Plasma exchange was higher in patients who were treated with rituximab (31.1 vs 13.68). Mild reactions were recorded in 78% of patients, including hypotension, chill, and urticaria.

There were 27 patients (23.6%) who experienced 1 or more relapses of TTP in the following 3 years after diagnosis, with a median time of 12.44 (range, 4-48) months to relapse. Female patients made up 83.3% of patients with at least 1 relapse. Patients who relapsed were significantly younger, with a median (IQR) age of 32 (17) years vs 34 (18) years.

The researchers found that age, platelet count, and reticulocyte count were associated with relapse in a multivariate logistic regression models. Patients who had greater than 30×10³ platelet count had less relapse compared with patients with less than that optimal cut off (odds ratio [OR], 0.222; 95% CI, 0.081-0.603).

Overall survival rate for patients with TTP was 73.7%, with the 1-month, 1-year, and 2-year survival totaling 82.5%, 76.3%, and 74.6% respectively. Mortality was associated with age, hematological initial presentation, and neurological initial presentation. Patients who were aged 55 years and older had significantly higher odds of mortality compared with those younger than 55 years (OR, 24.923; 95% CI, 7.196-86.325).

There were some limitations to this study. Most patients only had a single initial measurement of ADAMTS13 done rather than a test every 3 to 6 months during disease remission.

The researchers concluded that the mortality and relapse rates of TTP in Iranian patients was similar to other existing reports. The lower platelet counts also acted as a predictor for long-term relapse in patients. This knowledge could help to mitigate the 21.1% relapse rate and 26.3% mortality rate in this population.

Reference

Shiraji ST, Rostami MR, Foumani HK, et al. Clinical features and risk factors of relapse and mortality in thrombotic thrombocytopenic purpura patients: a seven-year experience. Int J Hematol Oncol Stem Cell Res. 2023;17(3):156-166. doi:10.18502/ijhoscr.v17i3.13305