A blood sample from a 54 year old female with ovarian tube cancer was tested for D-dimer using Nycocard Reader II. The result was 2,100 ng/mL, a sudden increase from the previous two days which was 500 ng/mL.
How could this happen?
- From the clinical aspect, the result might be caused by the patient experiencing constant fibrin formation and degradation due to her cancer.
- From the laboratory aspect, the result might be caused by several errors.
Nycocard Reader II uses a membrane coated with anti-D-dimer antibody. When a patient’s plasma is added, D-dimer from the plasma will bind the antibody. A solution containing anti-D-dimer antibody labeled with gold then added to the membrane. The antibody will bind the D-dimer already immobilized on the membrane, forming a sandwich complex. Any fluid excess will pass through the membrane and absorbed by a paper layer beneath the membrane. Gold that is trapped in the membrane will darken its color, of which intensity is proportional to the D-dimer level in the plasma.
Errors can originate from the sample or the procedure:
* The sample can still have too many cells, is lipemic, or too viscous, causing less membrane penetration and more gold to be immobilized, generating false high result. If this is indeed the case, you will notice that the plasma takes longer to be absorbed by the membrane than usual (> 50 seconds).
A lipemic sample also has some degree of color intensity that will further contribute to a false high result.
* Nycocard Reader II employs some degree of manual work in its procedure. There are three steps of pipetting that are done by hand. This can cause imprecise results.
What can be done?
- If the problem is a sample that still has too many cells or too viscous, re-centrifugation at 2000 g for 15 minutes may solve the problem.
- I don’t know any solutions for a lipemic sample.
- If the problem is less than adequate pipetting, repeating the test with steadier hands will solve the problem.
How could this happen?
- From the clinical aspect, the result might be caused by the patient experiencing constant fibrin formation and degradation due to her cancer.
- From the laboratory aspect, the result might be caused by several errors.
Nycocard Reader II uses a membrane coated with anti-D-dimer antibody. When a patient’s plasma is added, D-dimer from the plasma will bind the antibody. A solution containing anti-D-dimer antibody labeled with gold then added to the membrane. The antibody will bind the D-dimer already immobilized on the membrane, forming a sandwich complex. Any fluid excess will pass through the membrane and absorbed by a paper layer beneath the membrane. Gold that is trapped in the membrane will darken its color, of which intensity is proportional to the D-dimer level in the plasma.
Errors can originate from the sample or the procedure:
* The sample can still have too many cells, is lipemic, or too viscous, causing less membrane penetration and more gold to be immobilized, generating false high result. If this is indeed the case, you will notice that the plasma takes longer to be absorbed by the membrane than usual (> 50 seconds).
A lipemic sample also has some degree of color intensity that will further contribute to a false high result.
* Nycocard Reader II employs some degree of manual work in its procedure. There are three steps of pipetting that are done by hand. This can cause imprecise results.
What can be done?
- If the problem is a sample that still has too many cells or too viscous, re-centrifugation at 2000 g for 15 minutes may solve the problem.
- I don’t know any solutions for a lipemic sample.
- If the problem is less than adequate pipetting, repeating the test with steadier hands will solve the problem.
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