Williams et al used clinical findings, laboratory data and the Plasmic score to evaluate patients with microangiopathic hemolytic anemia (MAHA) These can help to distinguish thrombotic thrombocytopenic purpura (TTP) from atypical hemolytic uremic syndrome (aHUS). The authors are from the University of Alabama at Birmingham.


Patient selection: microangiopathic hemolytic anemia (MAHA)


Criteria for MAHA

(1) anemia

(2) schistocytosis (>= 2%)

(3) evidence of hemolysis (decreased to absent haptoglobin, elevated serum LDH, elevated serum indirect bilirbuin)


A patient with MAHA should have testing done for ADAMTS13.


Indications for emergent plasma exchangte:

(1) platelet count < 30,000 per µL

(2) serum creatinine < 2.0 mg/dL

(3) Plasmic score >= 5


A person who does not meet these indications can be started on plasma exchange if clinically indicated.





< 10%


daily plasma exchange, immunosuppressive drugs

>= 10%

atypical HUS

discontinue plasma exchange, start eculizumab, monitor renal function


Problems in diagnosis:

(1) red blood cell changes in iron deficiency may be mistaken for hemolytic schistocytosis

(2) pre-existing elevation of INR and/or serum creatinine can result in a low Plasmic score in the presence of TTP


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