laboratory findings

Last reviewed 01/2018

• prolonged prothrombin time
• prolonged partial thromboplastin time - but less so than for PT
• fibrinogen level, thrombin time and platelet count are unaffected

If the prothrombin time is prolonged, there are two alternatives for determining if vitamin K deficiency is the cause:

• positive response to therapeutic trial of vitamin K supplements
• plasma radioimmunoassay of the non-carboxylated precursor of prothrombin; shown to be at increased concentration