D-dimer

Pathology category

Haematology

Code

DD

Referral code

Request form

ICE/StandardA Clotting Screen is required with all D-dimer requests (Code CS) - no additional sample necessary

Test information

D-dimers are reported using Age-related cut off values (see reference range below)‘A normal value excludes the diagnosis of DVT in a patient who has a low clinical probability of having DVT. This high negative predictive value is useful to reduce the need for further wasteful imaging or immediate anticoagulation with its associated risks. A positive D-dimer test, when combined with a low clinical probability for DVT, should prompt the clinician to proceed with advanced confirmatory imaging.Regardless of the patient group, D-dimer has a low positive predictive value. However, the positive predictive value is even lower in the presence of other clinical conditions that may elevate serum levels such as cancer, infection, ischaemia, end-stage renal or liver disease, and trauma, and is, therefore, not recommended in these patients.’Taken from BMJ best practice

Guidelines

Pre-analytical

Must be analysed within 4 hours of collectionLipaemic, jaundiced and haemolysed samples may have problems with testing.Sample transport should be at 4-25C and reach the laboratory ASAPPlease note: the samples must arrive the same day as collection otherwise they will be rejected by the laboratory

Reference range

Age (Years) D-dimer (ng/ml) <60 <500 61-70 <600 71-80 <700 81-90 <800 >90 <900

Tube type

Tube type info

2.7ml blue top citrate1.8ml paediatric citrate bottle (white cover)1.0ml sodium citrate tube (microcollect)

Special requirements

D-Dimer should not be used in pregancy or in patients on anti-coagulants

Minimum volume

1 tube minimum 90% full, can be added to INR/APTT but essential to ensure full sample

Assay frequency

Routine

TAT Inpatient (urgent)

1 hour

TAT Inpatient

4 hours

TAT GP/Outpatient

4 hours - positive results will be telephoned

Referral lab

local