Page 555 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 27 ■ Principles of Hemostasis and Thrombosis: Blood Coagulation Factors and Natural Coagulant Systems 539

Fibrinogen D E D BOX 27.2

Fibrin Clot D D E D D Conditions That Can Generate Falsely

(Cross-Linked) Decreased or Falsely Increased D-Dimer
Values

E D D E
FALSELY DECREASED VALUES

■ Anticoagu ant thera y
E S a er, o er, non rogressing thro bus
D-Dimer ■

Fragments D D
D D FALSELY INCREASED VALUES

FIGURE 27.6 Basic structures o brinogen, cross- inke brin ■ Various isease states

c ot, an the d- i er. ■ Postthera eutic c inica roce ures

activation o the brino ytic syste , d- i er rag ents are ecrease or a se y e evate d- i er va ues). It is ore

re ease ro the c ot an circu ate in the b oo . i ortant to e i inate a se y ecrease va ues than a se y

Laboratory assay o d- i ers has been estab ishe to he e evate ones.

in the iagnosis o DIC an ee venous thro bosis ( DV )

or u onary e bo is (PE). T e qua itative an se i- Global Testing

quantitative d- i er assays are use u in the con r ation

o DIC. T e ra i , sensitive quantitative d- i er assay has T ro bosis an he orrhage are ajor contributors to or-

been eve o e to he exc u e DV an PE. T e resence bi ity an orta ity. y ica coagu ation testing (AP ,

o d- i ers suggests that a coagu ation- brino ytic rocess P , an ) arti cia y co art enta izes the intrinsic

is taking ace but oes not con r that a thro bus has an extrinsic coagu ation athways. T ese c ot-base assays

or e . easure initiation o c otting to the or ation o a brin c ot.

Assays use in the c inica aboratory to easure the Move ent towar ore ra i assays has increase coagu a-

d- i er rag ent can be ivi e into the o owing: tion oint-o -care testing, articu ar y in surgery.

T e intro uction o g oba testing instru ents a resses
1. Qua itative (se iquantitative) the entire he ostasis rocess inc u ing coagu ation, brin

2. Quantitative
or ation, an brino ysis. In a ition, actors such as

Qua itative assays (e.g., tra itiona atex agg utination) are the e ect o anticoagu ants an ate et unction are a so

anua etho s in which the en oint is etecte visua y. a resse .

Because o ease o use an ow cost, these etho s have been

wi e y a o te . Because o the otentia or user variabi - Throm boelastography, Throm oboelastom etry

ity an ess than i ea sensitivity, these assays are gra ua y (Viscoelastic Tests)

being re ace with newer, ore sensitive auto ate quan- A etho to onitor the yna ics o the co ete coagu a-

titative assays. tion rocess in who e b oo is ca e thro boe astogra hy.

Newer auto ate etho s are base on onoc ona anti- racings o the ove ent over ti e ref ect the characteris-

bo ies an icrosco ic atex- ight scattering etho o ogy. tic gra h, ro which the start o c ot or ation an axi-

Quantitative d- i er assays ay be re erre to by the syn- a stabi ity o the c ot can be rea . T e etho a so etects

ony s o i unoturbi i etric, icro atex i unoassay, gra ua reso ution o the c ot ue to brino ysis (Fig. 27.7).

or turbi i etric assays. In 1997, the rst sensitive auto ate T ro boe astogra hy is beco ing an i ortant too in

quantitative assay was a rove by the U.S. Foo an Drug etecting coagu o athies an gui ing he ostatic thera y at

A inistration (the S A Liatest D-DI assay, Diagnostica the oint o care. A itiona y, it has been shown to etect

Stago, Parsi any, NJ). Now severa assays are on the arket excess he arin e ect.

that use i unoturbi i etric techno ogy. Current y, two se iauto ate co ercia evices are

T e negative re ictive va ue o the auto ate assays on the arket—the thro boe asto etry (RO EM ana yzer,

is exce ent. d- i ers are resent in any atients with EM internationa , Munich, Ger any) an the thro b-

ongoing isease rocesses or who have un ergone an inva- e astogra hy ( EG ana yzer, Hae onetics Cor ., Braintree,

sive roce ure, but these atients o not nee to be su er- MA). Either etho easures the ca acity o the coagu-

ing ro DV or PE. In a ition, the quantitative d- i er ation rocess in ter s o axi a brin c ot. During the

assay shou not be use in atients receiving anticoagu ant ast ew years, these tests have been shown to be suitab e or

thera y (e.g., war arin or he arin), because they wi have etecting an treating coagu o athy in trau a care, car iac

ecrease circu ating d- i ers an can generate a a se y surgery, an iver trans antation, articu ar y in atients

ow va ue (Box 27.2 or con itions that can generate a se y with ow brinogen eve s.