Page 710 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

694 PART 8 ■ Fundamentals of Hematological Analysis

COAGULATION PROCEDURES (continued)

REFERENCES Procedure

1. Place an aliquot o 0.025 M calcium chlori e in a test tube

Brecker G, Cronkite EP. Morphology an enumeration o human bloo an incubate at 37°C or a minimum o 5 minutes an a

platelets. J Appl Physiol, 3:365, 1950. maximum o 60 minutes.

Henry JB (e .). Clinical Diagnosis and Management by Laboratory 2. Pipette 0.1 mL o the partial thromboplastin substrate into
Methods, Phila elphia, PA: Saun ers, 1984:1444. a test tube an incubate or 2 minutes.

Seivar CE. Hematology for Medical Technologists, 4th e , Phila elphia, 3. Pipette 0.1 mL o patient or control plasma into the sub-

PA: Lea & Febiger, 1972:429–432.
strate. Shake briskly to mix. Begin timing or exactly

COAGULATION PROCEDURES: ACTIVATED 5 minutes.

PARTIAL THROMBOPLASTIN TIME 4. A er 5 minutes o activation, trans er 0.1 mL o pre-

Principle warme calcium chlori e to the mixture. Immediately
begin to time with a stopwatch. Insert nichrome loop an
Te AP proce ure measures the time require to gener- sweep it across the bottom o the tube at the rate o two

ate thrombin an f brin polymers via the intrinsic pathway. times per secon .

Although a partial thromboplastin time test can be per- 5. At the f rst appearance o f brin, stop the stopwatch.

orme , contact actors can be activate more thoroughly Recor the number o secon s. Repeat this proce ure

by the a ition o substances such as kaolin in the activate (steps 2 through 5) or each assay.

orm o this assay.

In the AP , calcium ions an phospholipi s that substi- Note: Per ormance o this test by automate metho s is

tute or platelet phospholipi s are a e to bloo plasma. T e escribe in Chapter 30.

generation o f brin is the en point. Clinically, the AP is Reporting Results

use to i enti y an quantitate ef ciencies in the intrinsic Re erence values are epen ent on the activator an phos-

clotting system an to control anticoagulant therapy.
pholipi reagents use ; however, 20 to 35 secon s is typically

Specimen normal. In some laboratories, ranges may be rom 28 to 42

Fresh plasma rom citrate whole bloo is nee e . Centri uge secon s, with 42 to 46 secon s being marginal.

unopene whole bloo specimens at 2,500 rpm or 20 min- Procedure Notes

utes. Promptly trans er the plasma to a labele plastic tube Sources of Error

an place in an ice bath until teste . Specimens shoul be Various sources o error inclu e poor specimen collection

teste within 2 hours o collection.
or storage, improper reconstitution an storage o reagents,

Reagents, Supplies, and Equipment reaction temperature, timing, an clot etection.

1. Partial thromboplastin substrate containing an activator Clinical Applications

(such as Platelin Plus Activator or automate AP rom Te AP is wi ely a vocate as the test o choice or the

Organon eknika Corp. or equivalent) control o heparin therapy. It is also important in the screen-

2. 0.025 M calcium chlori e ing prof le o prekallikrein; high-molecular-weight kinino-

3. Ice bath gen; actors XII, XI, IX, VIII, X, V, II, an I; an inhibitors

4. (I manually per orme ) Stopwatch, 12 × 75-mm test against these actors.

tubes, nichrome loop, 0.1-mL pipettes, an a 37°C water

bath or heat block
BIBLIOGRAPHY

Quality Control

T e routine testing o control materials is essential. Both nor- Provi e on this book’s companion Web site at http://thepoint.

mal an abnormal controls shoul be teste simultaneously lww.com/ urgeon6e.

with patient specimens. Results within an outsi e the nor-

mal range are equally important to monitor. ANTITHROMBIN III: CLOTTING ASSAY METHOD

Commercial normal an abnormal control plasmas Principle

shoul be use or a comprehensive quality control program. In the presence o heparin, thrombin is neutralize at a rate

o prepare these controls, reconstitute normal an abnormal that is proportional to the antithrombin (A III) concentra-

plasma with the exact amount o reagent-gra e water speci- tion. Following ef brination, plasma is assaye in a two-stage

f e on the label. Allow to stan or 30 minutes at room tem- proce ure that utilizes stan ar ize amounts o heparin,

perature. Swirl gently to ensure complete rehy ration. Mix f brinogen, an thrombin. T e resulting clotting time is inter-

gently be ore use. Store rehy rate vials at 2°C to 8°C an use prete using a calibration curve. Clinically, the A III assay is

within 24 hours. Unopene vials shoul be store at 2°C to use ul prior to an subsequent to treatment with heparin in

8°C an use be ore the expiration ate on the label. cases o isseminate intravascular coagulation (DIC).