Activated Partial Thromboplastin Time (APTT)

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Activated Partial Thromboplastin Time (APTT)

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Activated Partial Thromboplastin Time (APTT)

Activated partial thromboplastin time (APTT) is the main screening test for the Intrinsic clotting system and is the second most common coagulation test being exceeded in frequency only by the prothrombin time.

APTT is a screening test which isolates the ‘intrinsic’ and ‘common’ pathways of the in vitro coagulation cascade model. Coagulation factors and cofactors within each pathway operate in concert to generate a fibrin clot endpoint, the time taken to form the clot being the APTT.

At Enfer Medical, APTT investigations are performed using validated laboratory methods, supporting accurate and timely coagulation analysis to inform clinical decision-making and patient management.

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Clinical Details

An elevated APTT may arise from a range of clinical, congenital, or pharmacological factors, including coagulation factor deficiencies, the presence of inhibitors, systemic disease states, and anticoagulant therapy. Common causes include:

Vitamin K deficiency
Liver disease
Disseminated intravascular coagulation (DIC)
Lupus anticoagulant
Autoantibodies or inhibitors against intrinsic pathway coagulation factors
Hereditary or acquired deficiencies of factors II, V, VIII, IX, X, XI, XII, prekallikrein, high molecular weight kininogen, or fibrinogen.
Certain subtypes of von Willebrand disease, secondary to associated factor VIII deficiency.

Anticoagulant therapy, including vitamin K antagonists, unfractionated heparin (UFH), low molecular weight heparin (LMWH), fondaparinux, direct thrombin inhibitors, and direct factor Xa inhibitors.

A shortened APTT (below the reference range) may be associated with:

Elevated levels of factor VIII, factor IX, or fibrinogen Sample activation during collection or handling.

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At Enfer Medical, we have integrated a cutting-edge and fully automated WASPLab® (Walk Away Specimen Processor) that has significantly enhanced our testing capabilities to ensure the highest of quality when processing patient samples.

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Our entire microbiology workflow has been optimized using automation and highly sophisticated robots to ensure uninterrupted incubation for rapid bacterial growth and improved turnaround times for patients.

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Sample Type &

Volume Required

Plasma: Citrated Plasma 3Ml; 3.2% trisodium citrate (Green or light blue Top depending on the manufacturer), filled to the required mark/line. Inadequately filled tubes cannot be tested.

Enfer Medical Test/Assays

Enfer Medical offers the ACL TOP 550 CTS.

Patient

Request Form

For clients using the Enfer Medical Client Portal, the Enfer Medical Patient Request Form (PRF) will be generated when you have completed your “Test Request” within the portal linked below.

Enfer Medical Portal

Please note that samples suspected of containing high risk pathogens such as Mycobacterium tuberculosis should be clearly identified on the form and packed separately from other samples.

24 hours

Results are available next working day.

7 Days a Week

This assay is available seven days a week.

Packaging

The packaging/preparation of samples for delivery to the laboratory are required to be in adherence to all national regulations for the safe transport of biological materials. HSE guidance can be reviewed HERE.
There are specific packaging instructions and labelling requirements requiring triple packaging including:

Primary leak-proof container – tube or vial containing the sample.
Secondary watertight container, with absorbent material, intended to protect the primary container.
Outer container protects the secondary container.
Patient Request forms must be placed between the secondary container and the outer shipping container.

Further information on the packaging/preparation of samples for delivery to the laboratory is contained within the Enfer Medical Laboratory User Manual which clients are provided with.

Storage & Stability

Specimens must be spun as soon as possible after collection. They must be centrifuged and testing performed within 4 hrs. of collection. If testing is to be delayed plasma can be frozen @-20°C and analysis can take place up to 7 days.

Transporting
Samples

In addition to the packaging of samples, the transport/delivery of clinical samples to the laboratory is required to be in adherence to all national regulations for the safe transport of biological materials. Enfer Medical provides a fully compliant logistics service, aligned with clients’ testing requirements.

Prompt transport of specimens:
To ensure prompt testing of samples and release of results within the published test turnaround times, samples should arrive to the laboratory by 18:00. Test turnaround time is measured from receipt of the sample at the laboratory until the time the authorised results are reported to users.

Acceptance/Rejection
of Samples

In rare cases specimens may not be suitable for testing on arrival to the laboratory. In that case the sample will be rejected at the receipt stage and the service user will be notified immediately and an explanation as to why the sample could not be processed will be provided. Reasons why samples cannot be processed include but are not limited to:

Samples received beyond the stability limits and/or not at the correct temperature indicated for each test.
Incorrect sample type received.
Leaking samples, sample not received or sample insufficient for analysis as stated below within sample requirements.
Non-compliant samples or request forms i.e. those missing sample date information, missing sample test request and/or missing sample site/type information.
Samples received without the necessary patient identifiers.

Clients will be provided with guidance on Sample Receipt Anomalies.

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Service

Health & Wellness

General health and wellness testing can include a variety of tests, depending on the needs of the individual or recommendations of

Find Out More

Service

Sexual Health

Regular STI screening facilitates early treatment and reduces the long-term consequences of infection.

Find Out More

Service

Respiratory Health

Rapid early pathogen identification has important treatment and infection control implications. See our range of tests here.

Find Out More

Service

Reproductive & Female Health

Hormonal analysis is hugely beneficial to identifying problems that can arise during the reproductive years.

Find Out More

Service

All Services

View the full suite of services at Enfer Medical here.......

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Result Values:

Quantitative results for APTT are reported in numeric value in seconds. Please contact us for more information on the reference ranges used at Enfer Medical.

Accessing

Your Results

Following receipt at the laboratory, results should be available on the next working day and will be reported to the referring clinician via the Enfer Medical Client Portal or in a format agreed with clients.

Homa IR (Calculated)

Established clients can login to the portal using the link above.