Knowledge Check • The Blood Project

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):

Schistocytes on smear

Elevated AST

Elevated direct bilirubin

Stool positive for Shiga toxin

Positive DAT

Increased reticulocytes

Elevated ALT

Low ADAMTS13

Spur cells in smear

Elevated ADAMTS13

Low haptoglobin

Elevated LDH

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.

What test(s) would you order to check for neurological involvement?

Click for Answer

CT/MRI brain

What test(s) would you order to check for cardiac involvement?

Click for Answer

Cardiac troponin
EKG
Echocardiogram

What test(s) would you order to check for renal involvement?

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BUN
Creatinine

Why is it recommended to order serology for HIV and hepatitis B/C?

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Because these viruses may cause thrombotic microangiopathy that mimics TTP