VIII WF = von Willebrand factor

(VIII C does not function in the absence of other parts).

¾ In hemophilia A the VIII C portion is defective so there

is lack of clotting activity but platelet function is normal.

¾ In von Willebrand’s disease VIII R: AG is missing so there

is abnormal platelet function alongwith lack of clotting

activity (VIII C portion does not function alone).

Laboratory Diagnosis of Hemophilia

¾ Activated partial thromboplastin time raised.

¾ Whole blood coagulation time prolonged in severe cases.

¾ Factor VIII clotting assay (VIII C) lowered.

¾ Immunological methods show normal VIII R: AG.

¾ Bleeding time and prothrombin time tests are normal

¾ Carrier females have half the clotting activity (VIII-C)

expected for the level of VIII R: AG.

Christmas Disease (Hemophilia B)

¾ Activated partial thromboplastin time prolonged

¾ Whole blood clotting time raised (in severe cases)

¾ Factor IX clotting assay diminished

¾ Both bleeding time and prothrombin time tests are

normal.

von Willebrand’s Disease

¾ Prolonged bleeding time

¾ Low levels of factor VIII clotting activity (VIII C)

¾ Low levels of factor VIII related protein VIII R:AG

¾ Defective platelet aggregation with ristocetin. The

aggregation response to other agents (collagen,

thrombin, adrenaline) is normal.

¾ In some patients there is defective retention of platelets

in glass bead columns.

Hemorrhagic Disease of Newborn

¾ The prothrombin time and activated partial thromboplastin time are both prolonged

¾ The platelet counts and fibrinogen levels are normal

with absent fibrin degradation products.

AUTOMATION IN COAGULATION ANALYSIS

Hemostar

Sleek, user-friendly coagulation analyzer based on turbophotometric detection of clot-based assays. Hemostar

has ten inbuilt incubation positions for sample and one

location for reagents (Fig. 10.1).

¾ It allows the user to make all basic tests for the analysis

of plasmatic hemostatic phase, e.g. Quick test (PT),

aPTT, TT, fibrinogen, defective factors, etc.

¾ It is a totally open instrument to be used with all kinds

of quality reagents, simply by following the producers

instructions.

306 Concise Book of Medical Laboratory Technology: Methods and Interpretations ¾ It includes a magnetic stirrer system in order to mix

well the reagents and plasma.

¾ Optical group: Made up of a Wolfram lamp at low

voltage and long self-life, an optical light pass, the

reaction cell holder and a solid state photocell which

registers all absorption changes produced.

¾ Thermostatic block: Thermostated device at 37 + 0.1°C

with magnetic stirrer motor built-in.

¾ Screen: Four digit indicator with tenth of second

precision, thermostatic block control temperature LED

(37°C) and two operation keys, the chronometer can be

used seperately to control incubation time.

¾ Tests: Quick Test (PT), aPTT, TT, Fibrinogen, deficiency

factors, etc.

¾ Power requirements: AC 220 V. 50 Hz 120 VA

¾ Dimensions: 180 × 300 × 140 nm

¾ Weight: 2, 3 kg.

Technical Features

System Automatic single channel coagulometer based

on turbo-photometric clot detection system

Measurement Opto-mechanical measuring system

Automatic start of measurement on addition of

reagent/sample for precise result

On screen digital chronometer to measure

tenth of a second accurately

Sensitivity Highly-sensitive in all measuring range because of Opto-mechanical measuring system

(combination of optical controls with mechanical movement of magnetic stirrers)

Incubator Inbuilt Incubator (solid state) fixed at 37°C

Incubator lodges 10 reaction cuvettes and

one reaction vial

Testing mode PT, APTT, TT, fibrinogen and factor assays

General

Lamp source Low voltage tungsten lamp

Detector IR detector

Motor For stirring action of magnetic stirrer

Display Back illuminated LCD with single row and

14 characters.

Power supply 220V, 50 Hz/60 Hz

Power consumption 50 VA

Serial output RS 232 standard

Working temperature 15 to 35°C

Dimensions 18 × 30 × 40 cm

Weight 2.2 kg

Hemostar XF