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PTT Results in Myeloma

Susan Buchholz sent this question Wednesday, January 21:

What should you do with prolonged PTTs on patients with multiple myeloma?

Thank you for your question, Susan. I’ve reviewed all my favorite references, and have reached no definitive global answers, so I will speculate and ask for contributions from our experts.

In plasma cell (multiple) myeloma, concentrated M-proteins may prolong clot-based assays.  if you are attempting to monitor heparin therapy using the  PTT (APTT), you can substitute the chromogenic anti-Xa heparin assay for an accurate result. If you are screening for a factor deficiency, no clot-based assay will work unless the patient has recently been pheresed to remove the M-protein. Then, results can be compromised by the reduction of coagulation factor activity or administration of normal plasma during pheresis. For some factor deficiencies, for instance, VIII or IX, chromogenic methods are available and are unaffected by M-protein. Finally, if you are using the PTT to screen for lupus anticoagulant, it won’t work even when the patient has been pheresed, and your best approach would be to depend solely on anti-cardiolipin antibody and anti-beta2-glycoprotein 1 antibody immunoassays.

I hope this is a start, and that some of our reference lab experts can contribute. Geo

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