Thrombotic Thrombocytopenic Purpura (TTP) and the Hemolytic Uremic Syndrome (HUS) feature microthrombi in small blood vessels and are associated with a poor prognosis if left untreated. Use of plasma exchange has improved survival, but the outcome may be affected by a number of clinical factors. The authors are from Barcelona, Spain.



(1) 32 patients treated with plasma exchange from 1980 to 1994.

(2) Data analyzed using Cox stepwise logistic regression.


Independent predictors of treatment failure:

(1) longer delay in initiating plasma exchanges

(2) presence of stupor or coma at the beginning of plasma exchange

(3) higher serum creatinine levels at the beginning of plasma exchange


Odds Ratio

95% CI

p value

stupor or coma


99.4 – 8955

< 0.001

delay in plasma exchange


1.44 – 1.73


serum creatinine


4.61 – 81.45


from Table 2, page 322; delay is based on the number of days from presentation prior to starting exchange; serum creatinine was based on intervals of < 2, 2.0 – 4.9, 5 – 10, and > 10 mg/dL.


Predictors of mortality:

(1) stupor or coma present at the beginning of plasma exchanges

(2) failure to treat with plasma exchanges


Interestingly, the following parameters did not correlate with prognosis (see prognostic scores in previous sections) in this series:

(1) hemoglobin levels

(2) platelet count

(3) serum LDH level


Steps to improve prognosis:

(1) early diagnosis

(2) prompt initiation of intensive plasma exchange


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