Page 550 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

534 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

Tese rag ents exert an antithro bin (A ) e ect, inhibit the 4. antithro bin

he ostasis syste through inter erence with brin ono er 5. C1 esterase inhibitor

o y erization, an inter ere with ate et aggregation. 6. Protein C inhibitor

S a a ounts o as in beco e tra e in the c ot. 7. Protein S inhibitor

Te s eci city o as in ensures that c ot isso ution occurs

without wi es rea roteo ysis o other roteins. P as in

a so activates the complement system, iberates kinins ro NOTE: This is a good time to complete Review Questions

kininogen, an can hy ro yze coagu ation actors V, VIII, an related to content in the preceding sections.

XII. Further c ot or ation is i e e by anti as ins an

natura y occurring inhibitors, so e o which revent the

activation o as inogen. T e natura y occurring inhibitors Laboratory Assessment of Blood

inc u e antithro bin (A ), a ha-2 acrog obu in inhibi- Coagulation Factors

tor, an a ha-1 antitry sin. P as in is not nor a y oun

in as a because it is neutra ize by an excess o inhibitors. C ot-base assays are o en use or eva uation o atients

with sus ecte b ee ing abnor a ities an to onitor anti-

Other Systems and Inhibitors coagu ant thera y. Most o these tests use citrate as a,

an the en oint or a o the is brin c ot or ation.
wo other syste s an roteases inhibitors have an e ect on C ot-base assays base on c ot or ation as the en oint

he ostasis an coagu ation. T e two a junct syste s are
are wi e y use in the c inica aboratory to eter ine the

1. Kinin syste integrity o the intrinsic or extrinsic athways o the coagu-

2. Co e ent syste ation syste . C ot-base an chro ogenic assays are use

ost o en. C otting assays rovi e an assess ent o coagu-

Kinin System ation unction, an chro ogenic tests are use to easure
the eve or unction o s eci c actors.
Te kinin system is activate by both the coagu ation an A wi e variety o b oo coagu ation actors such as
brino ytic syste s. F etcher actor ( reka ikrein) an thro bin ti e an a quantitative brinogen concentration

Fitzgera actor (HMWK) are a so nee e to enhance or assay, can be assesse by various aboratory roce ures (see
a i y the contact actors invo ve in the intrinsic syste . Cha ter 32, Laboratory Manua ). T e two ost co on y

Factor XIIa in the resence o HMWK converts reka ikrein er or e roce ures are the prothrombin time (P ) an the
to ka ikrein. Ka ikrein ee s back to acce erate the conver- activate artia thro bo astin ti e (AP ).

sion o actor XII to XIIa, which acce erates the intrinsic sys-
te rocesses. Activation o actor XII acts as the co on Prothrom bin Tim e

ath between any co onents o the he ostatic echa- Te P is the basis or the international normalized ratio (INR)
nis , inc u ing the brino ytic syste , the kinin syste , an use to onitor war arin anticoagu ant thera y an coagu a-

the co e ent syste .
tion actor e ciencies an as a iagnostic too or isor ers

Com plem ent System such as iver isease.
T e P roce ure eva uates the generation o thro bin
Co e ent aci itates ce e brane ysis o antibo y- an the or ation o brin via the extrinsic an co on

coate target ce s. wo in e en ent athways o co e- athway. T ro bo astin reagent is use or this assay.
ent activation, the c assic an a ternate athways, can T ro bo astin can be re are by various etho s: tissue

occur a ong with a co on cyto ytic athway. extraction o rabbit brain or ung, tissue cu ture, an o ecu-
P as in activates co e ent by c eaving C3 into C3a

an C3b. C1 esterase inhibitor inactivates co e ent an ar etho s. T ro bo astin reagent is a ixture o tissue
actor( F), hos ho i i , an ca ciu ions an is use to
a so has a ro e in he ostasis.
initiate c otting easure as the P . T ro bo astin or s

Protease Inhibitors co exes with an activates actor VII. T is rovi es sur-
aces or the attach ent an activation o actors X, V, an II.
Because the brino ytic syste is activate when the coagu- T ro bo astin, erive ro tissues that su y hos ho-
ation casca e is activate , extra brin is egra e an e i i- i o rotein, an ca ciu are a e to the b oo as a. T e

nate a ong with so e coagu ation actors. Enzy es such as ti e require or the brin c ot to or is easure .
as in an ka ikrein sti circu ate unti they are e i inate Re erence ranges are ro 10 to 13 secon s. Pro onge

by various echanis s: iver he atocytes, ononuc ear resu ts can in icate a e ciency o one or ore actors in the
hagocytic ce s, or serine rotease inhibitors resent in the extrinsic athway: actors VII, X, V, an II or I. Pro onge

as a. Serine rotease inhibitors attach to various enzy es va ues wi be seen i an ora anticoagu ant such as cou a-
an inactivate the . Serine rotease inhibitors inc u e
rin or a cou arin-containing substance (e.g., rat oison) is

1. α-Anti as in ingeste .

2. α-Antitry sin Carriers o a oint utation in the rothro bin gene,

3. α-Macrog obu in Prothrombin 20210, were iscovere in 1996 because these