Decision Tree of Hong et al for a Patient with Microangiopathic Hemolytic Anemia and Possible Thrombotic Thrombocytopenic Purpura

Patient selection: microangiopathic hemolytic anemia

Parameters:

(1) absolute immature platelet count

(2) clinical history

(3) ADAMTS13 activity in percent of normal

(4) absolute immature platelet count ratio (absolute IPC ratio)

absolute immature platelet count =

= (percent of platelets immature) * (platelet count per liter)

absolute immature platelet ratio =

= (current absolute immature platelet count) / (admission absolute immature platelet count)

Initial screen is positive if one or both are present:

(1) absolute immature platelet count less than 5 * 10^9/L (5,000 per µL)

(2) no clear cause (infection, malignancy, hypertension, etc)

If the absolute immature platelet count is >= 5 * 10^9/L AND there is a possible cause, then the underlying cause should be treated.

If the initial screen is positive, then

(1) monitor ADAMTS13 activity

(2) monitor absolute immature platelet count ratio

(3) start therapeutic plasma exchange (TPE)

where:

• An ADAMTS13 activity < 10% is severe; an activity 10-40% is moderate; an activity of 40 to 67% is mild.

• Not all combinations are shown. < 10% ADAMTS13 and < 3 AIPCR might be with Group C. > 67% ADAMTS13 and > 3 AIPCR might be indeterminate.

• ADAMTS13 activities of 40 to 67% are not shown. An absolute IPC ratio < 3 should probably be treated as C. An absolute IPC ratio >= 3 would be indeterminate.

• Absolute IPC ratio = 3 is not shown in table. Made >= 3 in implementation.