From “Cristina:” What is the reason why lipemic and hemolyzed coagulation sample should be rejected? Is it only the D-dimer is susceptible? Thanks.
Hello, and thank you for your question. Lipemia is likely to cloud the final reaction solution in a photo-optical method, interfering with the results. On all instruments, the quantitative D-dimer is a photo-optical assay, thus you cannot trust the results when lipemia is present. Companies that produce photo-optical measurement instruments select high or multiple wavelengths which are less affected by moderate lipemia.
Visible hemolysis not only may interfere in a photo-optical reading, it also implies the ex vivo activation of platelets and coagulation factors, rendering coagulation results invalid in electro-mechanical instruments as well as in photo-optical instruments.
For more on blood specimen management, I invite you to see our audio module,Hemostasis Blood Specimens. Geo.
Jul 8 2012
Comments (3)
Fibrinolysis
Hello Cristina,
George is perfectly right, but I would like
Hello Cristina,
George is perfectly right, but I would like to emphasize a few of his points.
It is the combination of a photo-optical together with the relatively low concentration of D-dimer that creates a problem with interfering substances. In a normal sample, the D-dimer concentration is typically 50 ng/mL (= 0.05 mg/L). In some respects this is very high, but for the immunoturbidimetric method that most D-dimer assays relay on, it is relatively low. In other words, this method is relatively insensitive. For this reason, to get a response, a fairly large volume of sample is needed in the cuvette of the coagulation instrument, and by doing this a large amount of e.g. lipids, hemoglobin and bilirubin will also be introduced into the cuvette (if present in the sample). These substances absorb light well at for instance 405 nm, which is the wavelength traditionally used in coagulation instruments. Newer instrument typically also have higher wavelengths as well, e.g. 700 or even 800 nm. By using the newer D-dimer methods that are adapted for these higher wavelengths, many of the problems that come with lipids and hemoglobin are completely avoided.
The ex vivo activation of platelets and coagulation factors does not affect the D-dimer results, as such, as George has pointed out in a different thread. / Göran
I also would recommend the article George cited in an earlie
I also would recommend the article George cited in an earlier post about heme binding factor VIII.
Plus red cells contain procoagulant phospholipid as well
Plus red cells contain procoagulant phospholipid as well