Activated Partial Thromboplastin Time

Pathology category

Haematology

Code

APTT

Referral code

Request form

Test information

Must be analysed within 8 hours of collection and will be rejected if over 12 hours old as per local SOPs

Guidelines

Pre-analytical

Lipaemic or jaundiced plasma may cause problems with testing

Haemolysed, underfilled  and clotted samples will be rejected

Sample transport should be at 4-25C and reach the laboratory ASAP

Please note: the samples must arrive within 8 hours of collection otherwise they will be rejected by the laboratory

Reference range

Time is reagent dependent.

Normal range = 24 – 37 secs

Normal ratio = 0.8-1.2

Tube type

Tube type info

2.7ml blue top citrate

1.8ml Paediatric citrate

Special requirements

Minimum volume

1 tube minimum 90% full (to the thick black line on the sample bottle) – this is essential to ensure correct ratio of anti-coagulant to blood (1:9 ratio)

Assay frequency

Routine

TAT Inpatient (urgent)

1 hour

TAT Inpatient

4 hours

TAT GP/Outpatient

4 hours

Referral lab

local