Activated Partial Thromboplastin Test

Activated partial thrombocplastin time (aPTT) measures the efficiency of the contact activation of clotting. It depends on factor XII, XI, IX, VIII, V and X.

Principle

Plasma is incubated with a substance like kaolin or elagic acid to bring about contact activation of factor XII to XIIa. XIIa cleaves XI to XIa. The subsequent steps in coagulation are calcium dependent and take place only when calcium is added. Phospholipid is added to provide a platelet sunstitute.

Method

The test involves mixing platelet poor plasma and a factor XII activator e.g. silica, celite, kaolin, micronized silica or ellagic
acid with phospholipid containing reagent. Calcium chloride is then added. The time take for a clot to form after adding calcium chloride is the activated partial thromboplastin time. The test is performed with paired samples one test and one control.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s