7
Figure 2. A suggested diagnostic and management strategy
for patients with LOW or INTERMEDIATE pretest
probability of immune TTP
Pretest probability of immune TTP should be determined based on clinical presentation and
laboratory results. If probability of TTP is low or intermediate, still consider TPE and corticosteroids,
but withhold caplacizumab until ADAMTS13 test results are available. If ADAMTS13 test is not
available, no caplacizumab should be started; if ADAMTS13 activity is <10 IU/dL (or 10% of
normal), consider adding caplacizumab and rituximab; if ADAMTS13 is ≥20 IU/dL (or 20% of
normal), no caplacizumab should be used and other diagnoses should be sought. If ADAMTS13 falls
borderline 10–20 IU/dL (or 10–20% of normal), consider other diagnoses, and further treatments
should be based on clinician's own clinical judgement. (All are conditional recommendations in the
setting of low certainty of evidence.)
Consider starting TPE + steroid
If ADAMTS13 activity result will
not be available (scenario B)
Do not add
caplacizumab.
Consider other
diagnoses
NEGATIVE
Activity >20 IU/dL
(or 20%)
BORDERLINE
Activity 10-20 IU/dL
(or 10-20%)
Use clinical judgement
to guide treatment.
Consider other
diagnoses
Consider adding
caplacizumab
Consider adding
rituximab
Do not start caplacizumab.
POSITIVE
Activity <10 IU/dL
(or <10%)
Patient with low or intermediate (<90%)
pretest probability of TTP
Evaluate pretest probability of TTP
Based on clinical judgement or a risk assessment model
If ADAMTS13 activity result
will be available within 72
hours (scenario A) OR
If ADAMTS 13 activity will be
available between 72 hours
and 7 days (scenario C)
Collect plasma sample
for ADAMTS13 activity
and inhibitors (or anti-
ADAMTS13 lgG). Do not start
caplacizumab until ADAM TS
13 activity is resulted
