Point-of care evaluation of coagulation: technical
aspects, indications, limitations, pitfalls
Andreas Calatzis
Institute for Prevention of Cardiovascular Diseases
University of Munich
Disclosure of commercial interest:
The author is a coinventor of the ROTEM and Multiplate analyzers
and CEO of Verum Diagnostica, Munich (manufacturer of the
Multiplate system), which is a 100% subsidiary of Roche.
Bleeding in Surgery
Causes




liver dysfunction
bone marrow dysfunction
renal dysfunction
hereditary disorders






trauma
hemodilution
consumption coagulopathy
heparin
artificial surface contact
anti-platelet drugs
clotting factors
concerns
platelets
fibrinolysis
Platelet Function
Main Mechanisms
positive
feedback
release of ADP
positive
feedback
formation of
Thromboxane A2
via COX
hemostasis during
operation, trauma,
menstruation,
after injuries
stent thrombosis
myocardial infarction
ischemic stroke
other ischemic events
aggregation via
GpIIbIIIa
(fibrinogen receptor)
Platelet Function Inhibitors
Main Mechanisms
positive
feedback
release of ADP
positive
feedback
formation of
Thromboxane A2
via COX
hemostasis during
operation, trauma,
menstruation,
after injuries
stent thrombosis
myocardial infarction
ischemic stroke
other ischemic events
aggregation via
GpIIbIIIa
(fibrinogen receptor)
Point-of-care testing – definition
Methods, which are applied
- in a near-patient setting
- in environments other than classical laboratories (e.g. ICU or OR)
- which can be applied by personnel without extensive laboratory
education (NB: national regulations may apply)
Synonyms
- „near patient testing“
- “bedside testing"
- "alternative site testing"
Point of Care Testing
why?
- fast availability of results
- targeted coagulation management (e.g. of bleeding
complications)
- simplified workflow (TAT shorter, no transport of
sample, no transmission of results between
laboratory and POC site), however additional effort
for performing the test at the point of care
Point of Care Testing
why?
- fast availability of results
- targeted coagulation management (e.g. of bleeding
complications)
- simplified workflow (TAT shorter, no transport of
sample, no transmission of results between
laboratory and POC site), however additional effort
for performing the test at the point of care
But:
- costs are often higher than for the
laboratory analysis
- important to define roles and
responsibilities
- quality management important
Point of care evaluation of coagulation – parameters
immunologic tests
D-Dimer
plasmatic coagulation
ACT, PT, aPTT
viscoelastic tests ´
ROTEM, TEG,
Sonoclot
platelet function tests
PFA-100 / 200,
Multiplate, Verifynow
Parameters that are available in the laboratory and in the POC
D-Dimer
PT and aPTT
Advantages:
-
short TAT
-
faster therapeutic decisions
-
in out-patient care: patient can get his result immediately,
therapeutic consequence can be discussed (e.g. Warfarin therapy)
Parameters that are available in the laboratory and in the POC
D-Dimer
PT and aPTT
NB:
-
only the INR is (relatively) well standardised
-
results of different aPTT, ACT, or D-Dimer assays should be reported
seperately in laboratory information systems or in the patient file to
circumvent misinterpretations (changes of the values which rely on
different assay systems could be misinterpreted as therapeutic
effects or changes in the course of disease)
Example: Differences between POC D-Dimer assays vs. the reference method
Int. Jnl. Lab. Hem. 2012, 34, 495–501
Parameters that are available in the laboratory and in the POC
D-Dimer
PT und aPTT
Not every instrument is equally well suited for the analysis of
hemodiluted samples or other altered samples from the ICU or OR
Applicability of the particular method in the context of the patient
sample should be verified (e.g. specifications by manufacturer,
publications, in house validation)
Activated Clotting Time (ACT)
blood + contact phase activation
 detection of clotting time

is mainly applied to monitor UFH therapy

several different instruments available: poor
standardisation

relatively weak correlation to actual heparin
concentration

low sensitivity towards LMWH or pentasaccharide
Viscoelastic methods: ROTEM, TEG and Sonoclot: Background
• mechanical, quantitative and
continuous assessment of clot
formation in whole blood
• coagulation activation, clot
formation and clot stability or
fibrinolysis are recorded
Viscoelastic methods: ROTEM, TEG and Sonoclot: Detection principle
• Clot firmness is continuously recorded via the elasticity (ROTEM / TEG) or
clot resonance (Sonoclot)
• ROTEM and TEG significantly more popular than Sonoclot
ROTEM
Principle:
Relative
movement of
Cup (7) and
Pin (6):
4,75°
Sonoclot principle
aus: Hartert H., Klin. Wochenschrift 26: 577−583 (1948)
aus: Hartert H., Klin. Wochenschrift 26: 577−583 (1948)
aus: Hartert H., Zschr. f. d. ges. exp. Medizin 117: 189−203 (1951
aus: Hartert H., Klin. Wochenschrift 26: 577−583 (1948)
Haemoscope TEG
2 channels
leveling required
manual pipetting
platelet mapping assay
very expensive
very few clinical
publications
ROTEM
 4 channels for parallel
tests
 robust detection system
using a ball bearing (ROTEM)
 electronic pipetting
ROTEM delta
4 channels
touch screen
broad menu of tests:
EXTEM
INTEM
HEPTEM
FIBTEM
APTEM
Single test reagents available
Viscoelastic methods: ROTEM, TEG and Sonoclot: Applications
Hemostasis
management in patients
with complex
coagulation disorders:
- trauma
- surgery (vascular
surgery, GI surgery,
orthopedics …)
- obstetrics
Viscoelastic methods: ROTEM, TEG and Sonoclot: pros and cons
+ comprehensive and clinically relevant
information on the coagulation status of
patients
+ increasing evidence on the improvements
in the coagulation management (less costs,
less bleeding) via a targeted coagulation
management vs. conventional “empiric”
coagulation therapy
+ implementation of viscoelastic methods
increases the understanding and education
on coagulation alterations in anesthesia and
intensive care
- low sensitivity for Warfarin, LMWH,
NOACs
- no detection of VWS, Aspirin, Clopidogrel
- additional efforts and costs
Percutaneous tracheostomy
•
•
•
•
Thrombo: 33.000/µl
PZ: 66%
aPTT:
40,4 sec
Fibrinogen: 413 mg/dl
Clinical case 1
Patient 68 years old, elective CABG x3, (ASA 100 mg 1xd)
extracorporeal circulation 99 min, ischemia 71 min, severe
postoperative bleeding
After 2 g Tranexamic acid and 4 g Fibrinogen
Stop bleeding
Clinical case 2
Patient 88 years old, elective aortic valve replacement and
CABG x 2, extracorporeal circulation 79 min, aortic clamp 54
min, severe postoperative bleeding
After 2 g Tranexamic acid and 4 g Fibrinogen
Stop bleeding
Clinical case 3
Patient 75 years old, rheumatic and ischemic heart disease,
elective mitral and aortic valve replacement + CABG x1,
extracorporeal circulation 184 min, aortic clamp 119min, severe
postoperative bleeding (myelodisplastic disease with
thormbocytopenia, Thrombocytes 42 G/l)
Platelets
5 units
Fibtem MCF OK
Thrombocytes 118 G/l
Stop bleeding
PFA-100/200
Principle
high shear rate
>5000 /s
Epinephrine
or
ADP
membrane with
collagen coating
red cell
platelet
FLOW



capillary
200µm

citrated blood is aspirated through a small aperture in a collagencoated membrane
Platelets adhere to the collagen surface and lead to a cessation of
blood flow
parameter = Closure Time (CT)
3 cartridges:
- EPI: costimulation by: shear stress, collagen, epinephrin
- ADP: costimulation by: shear stress, collagen, ADP
- P2Y: costimulation by: shear stress, ADP, PGE1 and Ca++.
Siemens PFA-100/200 Innovance P2Y Cartridge
No predictivity for stent thrombosis or bleeding
n=588
Popular study.
JAMA. 2010 Feb 24;
303(8):754-62.
updated data from
06-2011
In the only clinical study so far on the new PFA-100 P2Y cartridge clopidogrel low responders
according to PFA-100 had less stent thromboses, less trokes and less target vessel
revascularisations compared to clopidogrel responders. The Kaplan-Meier curves divided only
after 190 days, which makes any use of this cartridge for the clinical management highly
questionable. There was no predictivity of the PFA-100 tests for bleeding events found in this
study.
PFA-100 / 200:
Pros / Cons
+ widely used easy-to use method
+ high sensitivity for von Willebrand Disease and Aspirin
- few studies with clinical endpoints
- most studies on prediction of bleeding are negative
- only clopidogrel test on the market that has never shown
predictivity for stent thrombosis
- main element of proof for preoperative screening
(Koscielny et al, CATH 2004) is actually statistically
wrong
Accumetrics Verifynow
Principle
Mixing Chambers/
Detection Well
Accumetrics Verifynow
Principle / Assays
 platelet function testing in whole blood
 optical detection of platelets aggregating
on fibrinogen-coated polystyrene beads
 fully automated
 one tube of blood (2 ml) required per test
Assays:
 Aspirin assay: stimulation of platelets by
arachidonic acid
 P2Y12 assay: stimulation of platelets by
ADP + PGE1
 IIbIIIa assay: stimulation of platelets by
iso-TRAP
Mixing Chambers/
Detection Well
Accumetrics Verifynow
Pros and Cons
+ very easy to use
+ some data on prediction of stent
thrombosis
-
most studies on prediction of bleeding were
negative
-
almost no data on use of Verifynow in
anesthesia
-
recently two large negative studies on the
clinical management of platelet inhibitors using
Verifynow:
-
GRAVITAS (Price et al, JAMA)
-
ARCTIC (Collet et al, NEJM)
Mixing Chambers/
Detection Well
Multiplate®
Detection principle
 analysis of platelet function
in whole blood
 twin impedance sensor
 platelets aggregate on metal
sensors and increase
electrical resistance
 platelet function
analysis on
surfaces
Multiplate®
analyzer
 5 channels for parallel tests
 electronic pipetting
 applicable for laboratory and
near patient analysis
Example: Near-patient use of Multiplate in combination to TEG
Multiplate
Main tests
TRAPtest
TRAP
TXA2
ADPtest
ADP
TXA2
ASPItest
Arachidonic
Acid
Aspirin ®
NSAID
activation
inhibition
Clopidogrel
Prasugrel
Ticagrelor
GpIIb/IIIa antagonists:
COX
Reopro ® (abciximab)
Aggrastat ® (Tirofiban)
Integrillin ® (Eptifibatid)
Multiplate tracings
Examples
TRAPtest
no
platelet
inhibition
113 U
ASPItest
102 U
ADPtest
89 U
17 U
100 mg
aspirin qd
139 U
134 U
31 U
75 mg
clopidogrel qd
98 U
100 mg aspirin
+ 75 mg
clopidogrel qd
89 U
8U
17 U
3U
3U
88 U
tirofiban
(Aggrastat® i.v.)
7U
case report:
trauma patient
H. Schöchl, AUVA Trauma Centre, Salzburg
case report:
trauma patient
52 yo male
• Motorcycle race
• multiple trauma
•
ISS: 34
 severe bleeding
H. Schöchl, AUVA Trauma Centre, Salzburg
case report:
trauma patient
52 yo male
• Motorcycle race
• multiple trauma
•
ISS: 34
 severe bleeding
laboratory analysis:
Hb:
10,4g
Plt:
193.000/µl
PT:
70%
aPTT: 31,4sec
Fbg:
127 mg/dl
 acceptable
H. Schöchl, AUVA Trauma Centre, Salzburg
platelet function ?
platelet function ?
platelet function ?
abnormal platelet function due to
dual anti-platelet therapy
most likely the reason for the
bleeding complication
1 month follow-up
OR 9.8
JACC 2009 Mar 10;53(10):849-56.
Am Heart J. 2010 Aug;160(2):355-61.
5-10 x increased
risk for ST, q-wave
MI and stroke for
clopidogrel
low-responders
(20% of the patients)
very low
(=prasugrel-like)
risk for
clopidogrel
„responders“
(80% of the patients)
Multiplate
Clopidogrel monitoring: prediction of bleeding
cut-off
TIMI major bleeding
500
500
0
0
200
200
400
400
600
600
800
800
1000
1000
1200
1200
2,0
300
300
major bleeding (%)
Number
Number of
of patients
patients (n)
(n)
400
400
Sibbing D et al, JTH 2010
n=2533
200
200
100
100
2.6x
1,5
P=0.005
1,0
0,5
n = 975
0,0
High
responders
n = 1558
Remaining
patients
0
0
0
0
200
200
400
400
600
600
800
800
1000
1000
platelet
ADPADP-induced
induced aggregation
ADP-induced
platelet aggregation
aggregation (AU*min)
(AU*min)
1200
1200
Cardiac surgery in patients pre-treated with thienopyridines
Prediction of excessive bleeding
„The main finding of our study is that
the MEA ADPtest in patients under
thienopyridine therapy undergoing
cardiac operations is independently
associated with the postoperative
bleeding and transfusion of fresh
frozen plasma and platelets after the
operation, and it provides an accurate
preoperative prediction of patients who
will suffer from excessive
postoperative bleeding.“
„Only 8% of the patients with an MEA
ADP test AUC greater than 31 U
experienced excessive bleeding.“
31 U
Ranucci M et al. Multiple electrode whole-blood aggregometry and bleeding in cardiac
surgery patients receiving thienopyridines. Ann Thorac Surg. 2011 Jan;91(1):123-9.
Anesthesia / Intensive Care
2012 guidelines
The Society of Thoracic Surgeons Clinical Practice Guidelines
“For patients on dual antiplatelet therapy, it is reasonable to make decisions about surgical delay based on tests of platelet inhibition
rather than arbitrary use of a specified period of surgical delay”.
Class of Recommendation IIa, Level of Evidence B
“Point-of-care testing to assess perioperative platelet function may be useful in limiting blood transfusion”.
Class of Recommendation IIb, Level of Evidence B
“Assessments of platelet function with devices such as … Multiplate analyzer, VerifyNow, and PFA-100 proved useful in predicting
increased bleeding risk”… Point-of-care platelet function testing can guide perioperative transfusion management and reduce blood
component utilization [77, 78]. … Multiplate analyzer, and PFA-100 are used as part of point-of-care–guided transfusion algorithms”.
Ann Thorac Surg. 2012 Nov;94(5):1761-81.
Clinical case 4
Patient 64 years old, elective CABG x5, (ASA 100 mg 1xd and
Plavix 75mg 1xd until operation), severe postoperative bleeding
OK
ADP receptor inhibition by clopidogrel
Platelets
5 units
Stop bleeding
Clinical case 5
NSTEMI CABG X4 after loading dose (180mg)
and 48h therapy of tigagrelor 90mg tid
8U
Strong ADP receptor ihnibition
Platelets 5 units
14U
Persist poor ADP receptor activity  potentially inhibition
of transfused platelets by the reversible ADP receptor
antagonist Ticagrelor (Brilique)
Mortality-free
survival rate
A prospective study of the use of point of care coagulation testing (including
Multiplate) for the management of coagulopathy in cardiac surgery –
Effect of point of care testing on mortality
n=100
Kaplan–Meier curve demonstrating survival by type of performed coagulation management
during the 6-month follow-up period (4% vs. 20%; p=0,013) .
Weber CF at al, Anesthesiology. 2012 Sep;117(3):531-47
A prospective study of the use of point of care coagulation testing (including
Multiplate) for the management of coagulopathy in cardiac surgery –
Effect of point of care testing on blood loss
Postoperative chest tube blood loss (ml)
2500
p = 0.021
n=100
Conventional
group
p = 0.003
2000
1500
Point-of-care
group
p = 0.015
1000
500
0
n = 50
n = 50
n = 50
6
n = 50
12
Time (hours)
Weber CF at al, Anesthesiology. 2012 Sep;117(3):531-47
n = 43
n = 35
24
A prospective study of the use of point of care coagulation testing (including
Multiplate) for the management of coagulopathy in cardiac surgery –
Effect of point of care testing on costs
Cumulative costs in Euro [€] for applied hemostatic therapies
conventional group
POC-guided group
Packed erythrocytes [72 €/U]
18,648
13,176
FFP [0.162 €/g]
13,530
4,665
PC [231 €/U]
28,755
15,123
Fibrinogen [233 €/g]
35,882
27,727
PCC [114 €/600 IU]
10,944
6,726
rVIIa [2,784 €/240 kIU]
44,544
5,568
Total blood products and
hemostatic therapy
155,531
76,397
̶
̶
4,093
2,427
155,431
82,918
3,109
1,658
ROTEM® test costs
Multiplate® test costs
Cumulative [€]
Mean costs per patient [€]
FFP = fresh frozen plasma; IU = international units; PC = pooled platelet concentrate; PCC = prothrombin complex
concentrate; rVIIa = recombinant activated factor VIIa concentrate.
Lower costs
in the guided
group
Platelet dysfunction before surgery
Consequences
Potential consequences:
Be prepared!




check that platelet concentrates / other therapeutic options are available
experienced staff?
less traumatic approach / surgical approach with good visability ?
consider to use less / no colloids / less aggressive hemodilution
Reversible reason for the dysfunction? (e.g. patient was on clopidogrel)
 consider waiting 1-3 days till the operation
Platelet function testing during bleeding complications
Consequences
Platelet function normal or close to normal:
 platelets are rather unlikely to be the cause of the bleeding
 check other reasons for bleeding first (plasmatic factors, fibrinolysis, fibrinogen, surgical
bleeding?)
Platelet function abnormal:
 platelets are a potential cause for the bleeding complication
 consider application of platelet concentrates or desmopressin (Minirin ®)
laboratory analysis
vs.
Point of Care analysis
usually lower reagent costs
usually shorter turn-around-time
personnel with education in laboratory analysis
allows the targeted management of coagulation
disorders
environment with established quality
management procedures
better understanding of the clinical context of
the samples which are analyzed (treatments,
preanalytics)
larger menu of tests available (antithrombin,
D-Dimer, fibrinogen)
analysis of “young” samples (samples analyzed
in the laboratory may be up to 3-4 hours old)
POC diagnostics are preferable when …
 the transport of the sample to a laboratory is not feasible or not practicable
or
 the POC diagnostics contributes to an improved patient treatment (time /
costs / targeted treatment)
> Choice of method
Question
?
Consequence ?
Ressources ?
- staff
- logistics
- know how
Urgency ?
Test
Consequence
thank you for your attention !
?
“A total of 5649 unselected adult patients
were enrolled to identify impaired
hemostasis before surgical interventions….
The sensitivity of the PFA-100: collagenepinephrine was the highest (90.8%) in
comparison to the other screening tests
(BT, aPTT, PT, vWF: Ag). The positive
predictive value of the PFA-100: collagenepinephrine was high (81.8%), but the
negative predictive value was higher
(93.4%). “
>100 x citations
“A total of 5649 unselected adult patients were
enrolled to identify impaired hemostasis before
surgical interventions….
The sensitivity of the PFA-100: collagenepinephrine was the highest (90.8%) in comparison
to the other screening tests (BT, aPTT, PT, vWF: Ag).
The positive predictive value of the PFA-100:
collagen-epinephrine was high (81.8%), but the
negative predictive value was higher (93.4%). “
What was evaluated?
anamnestic
evaluation
coagulation tests
 no significant difference between PFA-100 in pts with and
without a bleeding history
 correlation with bleeding was not evaluated
??? where do the 90% sensitivity come from ???
 no significant difference between PFA-100 in pts with and
without a bleeding history
 correlation with bleeding was not evaluated
??? where do the 90% sensitivity come from ???
patients with abnormal
coagulation tests were
stratified as “impaired
hemostasis”. Then based
on the same tests that
were used to define
“impaired hemostasis” the
sensitivity and specificy
was calculated
 no significant difference between PFA-100 in pts with and
without a bleeding history
 correlation with bleeding was not evaluated
??? where do the 90% sensitivity come from ???
using this method a
dice would also have
90% sensitivity and
specificity
patients with abnormal
coagulation tests were
stratified as “impaired
hemostasis”. Then based
on the same tests that
were used to define
“impaired hemostasis” the
sensitivity and specificy
was calculated