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Anti-Xa and Lipemia

From “McDowekm:”

We currently perform anti-Xa heparin testing on a hybrid curve using Stago’s Rotachrom reagent on our Stago Compact. If we have a specimen that is lipemic, it can falsely increase the anti-Xa result. Can these specimens be ultra-centrifuged to obtain a more accurate Anti-Xa result?

Hello and thank you for your question. It would be helpful to review your data that indicate lipemia is raising your anti-Xa results. When performing the Rotachrom assay according to published protocols using the hybrid curve, the original specimen reaches a final dilution, counting diluents and reagents, of 1:22. Given this dilution, and according to the manufacturer’s package insert, interference will occur only when the original triglyceride concentration rises to above 360 mg/dL. Also, because the color intensity of the reaction is inversely proportional to heparin concentration, lipemia would be expected to reduce, not raise the anti-Xa result. Your data could substantially support or refute these claims.

I received some help on this question from Dave McGlasson at Wilford Hall USAF Medical Center in San Antonio, and he made an interesting observation about ultra-centrifugation. Ultra-centrifugation activates platelets, causing them to release platelet factor 4 (PF4), which neutralizes heparin. Thus, ultra-centrifugation of specimens for heparin assay is likely to falsely reduce heparin results. I hope this is helpful. Geo.

Comments (2)
Nov 23, 2010 5:22am

We are using the STA-Rotachrom Hybrid Heparin Assay Procedur
We are using the STA-Rotachrom Hybrid Heparin Assay Procedure provided to us by Stago. One of the limitations listed is “Lipemia may over-estimate the amount of heparin present.” It does not describe why this is true.

If we prepare platelet poor plasma and then proceed to ultrafuge only the PPP, would that be sufficient to limit the PF4 release that could affect the Anti-Xa result?


Nov 18, 2010 12:10pm

If the testing site for anti-Xa testing is using the S-Hybri
If the testing site for anti-Xa testing is using the S-Hybrid curve and the STA-Rotachrom reagents the final dilution of the lipemic specimen would be 1:36. I find it highly unlikely that with this dilution there would be lipemic interference.

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