Re-examination of 30-day survival and relapse rates in patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome

Abstract

Background and objectives: Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are characterized by microangiopathic hemolytic anemia and thrombocytopenia. Interestingly, markedly different survival rates have been reported despite increases in survivability. We studied TTP-HUS 30-day mortality and relapse rates of patients who received TPE at our institution and compared them to published data.

Patients and methods: Retrospective study analyzed 30-day mortality and relapse rates attributed to TTP-HUS from 01/01/2008 to 12/31/2012 and compared them to comparable literature reporting mortality and survival. Studies describing other etiologies for TPE and different mortality time interval were excluded.

Results: Fifty-nine patients were analyzed and all were initially treated with TPE and corticosteroids. Eleven patients were classified as not having TTP-HUS due to testing or clinical reassessment which ruled in other etiologies, and 18/59 patients had ADAMTS13 activity <10%. Of remaining patients, 36/48 (75%) were diagnosed as idiopathic and 12/48 (25%) as secondary TTP-HUS. Patients received a mean of 12 TPEs (range 1-42); 42/48 (87.5%) patients had ADAMTS13 activity measured; complete response obtained in 39/48 (81.2%) patients (platelet count >100 x 10(9)/L); partial response in 4/48 (8%); and 5/48 (10.4%) did not have increases in platelet counts (2/5 of these patients died within the study period). Forty percent of patients obtained platelet counts >150 x 10(9)/L. Overall 30-day mortality for our patient cohort was 6.7% (4/59). Comparison of our mortality rate to combined data of five published studies of 16% (92/571) showed a significant difference, p = 0.04. Our relapse rate was 18.6% (11/59) similar to previous reports.

Conclusions: Wide differences in mortality may be due to grouping of two distinct pathologic entities under TTP-HUS; and presence of confounding factors in the patient populations under study such as co-morbidities, promptness of TPE initiation, delay in diagnosis and therapeutic practice.

Fig 1. Study selection dendrogram used for data comparison.

All five studies reported 30-day mortality and relapse in their study cohorts.

Fig 2. Thirty-day mortality and relapse in TTP-HUS.

Thirty-day mortality attributed to TTP-HUS was 2% (1/48); however, overall mortality for patient cohort was 6.7% (4/59) (3 patients died of causes unrelated to TTP-HUS diagnosis (engraftment failure and graft vs. host disease, multi-organ failure due to sepsis and bacteremia, and heart failure due to worsening ejection fraction). Pooled 30-day mortality rate is 16.1% (92–571), p = 0.04. Relapse rate between our entire patient cohort (18.6%) and that of pooled data (14.3%).