Activated Partial Thromboplastin Time (APTT) - Black Country Pathology Services

Investigation Name:Activated Partial Thromboplastin Time (APTT)

Alias or Abbreviation:APTT

Accreditation:UKAS ISO15189:2022 Accredited test: On scope

Intro:

The Activated Partial Thromboplastin Time (APTT) test is used to assess the intrinsic and common pathways of the coagulation cascade. It is commonly requested to investigate unexplained bleeding or thrombosis, and to monitor patients receiving unfractionated heparin therapy. It also aids in detecting deficiencies of clotting factors such as VIlI, IX, XI, and or the presence of circulating inhibitors, including lupus anticoagulants.

In the laboratory, automated coagulation analysers are used to measure clotting time. Patient plasma is incubated with a reagent containing a contact activator and phospholipids, which initiates the intrinsic pathway upon the addition of calcium. The reagent is sensitive to reduced levels of contact factors, intrinsic and common pathway factors, the anticoagulant effect of heparin, and the presence of inhibitors-particularly lupus-like anticoagulants.

Pathology Laboratory:Haematology Laboratory

Requestable Seperately?No

Part of Profile:Coagulation Screen

Tests in Profile:APTT and APTT Ratio

E-Requesting Tab:BASIC-Blds

Lower Reference Range Limit:25

Upper Reference Range Limit:35

Units:seconds

Minimum Sample Volume:Filled to line on bottle

Expected Turnaround Time:< 4 hours

Test Code:APTTH

Sample Type:

Sodium Citrate Tube (Blue top)

Maximum Add on Time:8 hours (4 hours if for heparin monitoring)

Complex Reference Range:If patient is on heparin then a heparin ratio will be reported.
Heparin Ratio range for patients is 1.5-2.5.

Age specific paediatric/neonatal reference range :-

Premature (24-29 weeks - Day 1) APTT 40.6 - 101 seconds
Premature (30-36 weeks - Day 1) APTT 27.5 - 79.4 seconds
Premature (30-36 weeks - Day 30) APTT 26.9 - 62.5 seconds
Full term (37-40 weeks - Day 1) APTT 31.3 - 54.5 seconds
Full term (37-40 weeks - Day 5) APTT 25.4 - 59.8 seconds

Collection Conditions / Other Information:Full sample should be tested within 4 hours of specimen collection. Please contact the haematology laboratory for any Urgent requests.

Paediatric sample tubes are available to order for children and difficult to bleed patients. These tubes require 1ml of blood to be taken.

Underfilled or overfilled samples will not be processed as the ratio of anticoagulant to blood in the tube will be incorrect.
Clotted and grossly haemolysed samples cannot be processed.
Haemolysis, Icterus and lipaemia may interfere with testing and so manual methods may be required to gain results.

Referred to Another Laboratory?No

Storage Requirements:Samples should be stored at room temperature and sent to the laboratory without delay.

EQA Scheme:UK NEQAS Coagulation

Site Sample Tested:New Cross Hospital - Haematology Laboratory
Walsall Manor Hospital - Haematology Laboratory
Midland Metropolitan University Hospital - Haematology Laboratory
Russells Hall Hospital - Haematology Laboratory