2. SCREENING TESTS SPECIAL TESTS
Whole blood
coagulation time
Prothrombin time and
INR
Activated partial
thromboplastin time
Thrombin time
Coagulation factor
assays
Quantitative assay
3. COAGULATION TIME PROTHROMBIN TIME
NORMAL – 4-9
MINUTES
It is done by various
capillary and tube
methods
Insensitive and non
specific hence not used
NORMAL – 11-13
SECONDS
It tests the adequacy of
extrinsic and common
coagulation pathways
Increased PT values
indicates deficiency of
factor v, vii ,x
,prothrombin or
fibrinogen
CAUSES OF
PROLONGED PT
Administration of oral
anticoagulant drugs ,
liver disease especially
obstructive liver
disease , DIC
4. (1)- BLEEDING TIME
.Normal value- 2- 6minutes
.Modified Ivy`s test
.Indicates time taken for a standardised skin
puncture to stop bleeding.
.A prolonged bleeding time may be due to-
-Thrombocytopenia
-Disorders of platelet
function
5. Tourniquet test for capillary fragility is performed
to identify disorders of vascular wall integrity or
platelet disorders.
Stasis is produced by inflating a
sphygmomanometer cuff around the arm in the
usual manner (between 80-120mm/hg).
This moderate degree of stasis is maintained for
5minutes
2.5cm diameter region of skin on the volar surface
of the arm 4cm distal to the antecubital fossa is
observed for petechial haemorrhages.
Presence of more than 20 petechiae is considered a
positive test.
6. SCREENING TESTS SPECIAL TESTS
Platelet count
Bleeding time
Examination of
fresh blood film
to see the
morphological
abnormalities of
platelets
Platelet adhesion
test
Aggregation test
Electron
microscopy
Prothrombin
consumption
index
7. NORMAL COUNT 150,000 TO 450,000/mm3
3 method are used to count the number of
platelets which include
DIRECT METHOD- whole blood is diluted and
platelets are counted
SEMI AUTOMATED METHOD-platelets are
subjected to sedimentation and coagulation
and then counted using electron particle
counter
FULLY AUTOMATED METHOD-platelets are
directly counted
8. If the screening test indicates a disorder of
platelet function the following tests are carried
out
(1)-PLATELET ADHESION TEST- such as retention
in a glass bead column
(2)-AGGREGATION TEST-which are turbidometric
techniques using ADP, collagen
(3)-Granular content of the platelets and their
release can be assessed by ELECTRON
MICROSCOPY
(4)- Platelet coagulation activity is measured
indirectly by PROTHROMBIN CONSUPTION INDEX
which provides information about first stage of
clotting, by measuring the amount of residual
serum prothrombin which remains after clotting
9. QUALITATIVE PLATELET DISORDERS
Most common cause of abnormal bleeding and
attributed to following causes
(1)-Decreased platelet production
(2)-Decreased platelet survival time
(3)-Increased platelet sequestration by spleen
(4)-Dilution of the platelet count by multiple
blood transfusions.
THROMBOCYTOPENIA THROMBOCYTOSIS
THROMBOCYTOPENIA
10. (1)-CONGENITAL HYPOPLASIA OF THE
MEGAKARYOCYTES IN THE BONE MARROW
-Fanconi syndrome
-Tar syndrome
(2)-INFECTIVE THROMBOPOIESIS
characterize by normal to increased
marrow megakaryocytes in association with
decreased circulating platelets
Found in
- Megaloblastic anemia
- Myelodysplastic syndromes and
leukemia
11. IMMUNOLOGIC THROMBOCYTOPENIA
NON-IMMUNOLOGIC THROMBOCYTOPENIA
occurs due to rickettsial , bacterial, viral
infections
IDIOPATHIC THROMBOCYTOPENIA PURPURA
TYPES
Acute ITP
Chronic ITP
Recurrent ITP
Neonatal ITP
DRUG INDUCED IMMUNOLOGIC
THROMBOCYTOPENIA
POST TRANSFUSION PURPURA
12. A platelet count increased above normal will
be found as a result of a variety of
circumstances.
REACTIVE
THROMBOCYTOSIS
AUTONOMOUS
THROMBOCYTOSIS
Generally responds when
the lying disorder is
treated
Marked increase in the
platelet count
Following splenectomy,
the platelet count will
rise during first
postoperative week
Associated with
thrombotic and
haemorrhagic
complications
Thrombocytosis
following major surgery
usually occurs during
first postoperative week
Common in
myeloproliferative
disorders that includes
- Polycythaemia Vera
-Myeloid metaplasia
THROMBOCYTOSIS
