Knowledge Check

Of the various lab tests, which is diagnostic of thrombotic thrombocytopenic purpura (TTP)?

a
Elevated LDH
b
Low haptoglobin
c
Elevated CRP
d
Low ADAMTS13 activity
Correct. ADAMTS13 activity < 10% is diagnostic of TTP.
e
Mutation analysis of ADAMTS13

Sort lab test (top) according to whether it is typically altered in TTP or not (bottom):

Elevated LDH
Stool positive for Shiga toxin
Elevated ADAMTS13
Spur cells in smear
Elevated ALT
Schistocytes on smear
Elevated AST
Increased reticulocytes
Elevated direct bilirubin
Positive DAT
Low haptoglobin
Low ADAMTS13
Elevated PT and/or aPTT
Altered in TTP
Not altered in TTP

Abbreviations: TTP, thrombotic thrombocytopenic purpura; LDH, lactate dehydrogenase; DAT, direct antiglobulin test; PT, prothrombin time; aPTT, activated partial thromboplastin time.

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