Review article

https://doi.org/10.11613/BM.2016.028

Interference of M-protein on prothrombin time test – case report.

Sandra Margetić ; Clinical Institute of Chemistry, Medical School University Hospital Sestre milosrdnice, Zagreb, Croatia
Ivana Ćelap orcid.org/0000-0002-3982-5777 ; Clinical Institute of Chemistry, Medical School University Hospital Sestre milosrdnice, Zagreb, Croatia
Lora Dukić ; Clinical Institute of Chemistry, Medical School University Hospital Sestre milosrdnice, Zagreb, Croatia
Ines Vukasović ; Clinical Institute of Chemistry, Medical School University Hospital Sestre milosrdnice, Zagreb, Croatia
Lucija Virović-Jukić ; University Department of Internal Medicine, Medical School University Hospital Sestre milosrdnice, Zagreb, Croatia

Abstract

The aim of this report was to present a case of interference on prothrombin time (PT) test that directed further laboratory diagnostics and resulted with final detection of monoclonal gammopathy in an 88-year old man. Routine coagulation testing during medical examination at Emergency Department revealed unmeasurable PT (< 7% activity) and activated partial thromboplastin time (aPTT) within reference range. After repeated sampling for coagulation testing, PT was unmeasurable again, as well as fibrinogen level (< 0.8 g/L), thrombin time (TT) was significantly prolonged (107 seconds) and aPTT was within reference range. In both plasma samples refrigerated at 4 °C overnight, white gelatinous precipitate was visible between the cell and plasma layers and the presence of monoclonal protein (M-protein) was suggested in our patient. Further laboratory diagnostics revealed total serum proteins at concentration of 123 g/L and the presence of M-protein IgG lambda (?) at concentration of 47.1 g/L. These results suggested monoclonal gammopathy as an underlying pathophysiological condition in our patient. Activities of coagulation factors II, V, VII and X were within reference ranges or increased. These results and correction of unmeasurable PT result to 67% in mixing test with commercial normal plasma suggest in vitro rather than in vivo interference of M-protein on PT result. In contrast, significantly prolonged TT results in all analysed samples suggest impact of M-protein on this global coagulation test due to possible effect on fibrin polymerization.

Keywords

prothrombin time; interference; M-protein; monoclonal gammopathy; thrombin time

Hrčak ID:

161696

URI

https://hrcak.srce.hr/161696

Publication date:

15.6.2016.

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