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):

Spur cells in smear

Positive DAT

Schistocytes on smear

Elevated ADAMTS13

Elevated LDH

Stool positive for Shiga toxin

Elevated AST

Low ADAMTS13

Elevated direct bilirubin

Elevated PT and/or aPTT

Increased reticulocytes

Low haptoglobin

Elevated ALT

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