D dimer

Hi all I have a question about the d dimer well a few years ago I had pain in my leg and went to hospital they did a d dimer which was positive they then gave me a scan which was clear but what I wondered was does any one know why else this could of been positive if scan was clear .when this happened I didn't even know I had ApS so didn't think to ask questions.

Xx

5 Replies

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  • Hi Moonbug,

    What type of scan/where did they scan? Maybe they're missed the clot or it could have moved before they looked for it? When my D dimer was positive they found clots in my lungs but when they scanned my legs for DVT they found none. I think certain things like inflammation, liver problems etc can give false positives. I'm sure there are more experienced Hughies that will chime in.

  • Hi Moonbug

    It is possible as Sassy suggests that clot had moved or they were looking in wrong place, also possible to have false positive and false negative D Dimer tests.

    I had dvt and PE, clot had already moved from leg to lungs by the time scan was organised and my D Dimer was negative!!!

    Aps a mystery within an enigma?!?!!

    Take care gentle hugs love Sheena xxxxx :-) :-) :-)

  • Hi Moonbug,

    It is possible to have a false negative D-dimer test as this had happened to me on each occasion the docs used a D-dimer test prior to me finally coughing up blood and then they gave me a VQ scan and discovered multiple PE's. Consequently no doctor ever uses a D-dimer test on me anymore. I did read that in some people who have anti-coagulated blood the D-dimer test will give a false negative result.

    As far as a false positive result, it may do that also, however when I was researching my own false negative result I also read that sometimes other things can effect a D-dimer test.

    This is where I got my information if you wanted to have a read,

    labtestsonline.org.au/under...

  • Yes, all of the above, pretty well covers your query. I have failed all tests for APS, despite my multiple clots with first pregnancy. Mary F x

  • D Dimer is frequently high without having any clots. I know mine tends to run high (positive) on a day to day basis.

    Here is a very general explanation from Wikipedia giving some causes:

    Various kits have a 93-95% sensitivity and about 50% specificity in the diagnosis of thrombotic disease.[7]

    False positive readings can be due to various causes: liver disease, high rheumatoid factor, inflammation, malignancy, trauma, pregnancy, recent surgery as well as advanced age[citation needed]

    False negative readings can occur if the sample is taken either too early after thrombus formation or if testing is delayed for several days. Additionally, the presence of anti-coagulation can render the test negative because it prevents thrombus extension.

    Likelihood ratios are derived from sensitivity and specificity to adjust pretest probability.

    In interpretation of the d-dimer, for patients over age 50 a value of ageX10 may be abnormal.[8][9]

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