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):

Increased reticulocytes

Stool positive for Shiga toxin

Spur cells in smear

Low haptoglobin

Elevated AST

Elevated ADAMTS13

Elevated ALT

Elevated LDH

Schistocytes on smear

Positive DAT

Low ADAMTS13

Elevated direct bilirubin

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?

Click for Answer

BUN
Creatinine

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

Click for Answer

Because these viruses may cause thrombotic microangiopathy that mimics TTP