A 67-year-old woman arrives at the emergency department with acute bleeding into the back of the throat.A coagulation screen is ordered with the following results:
$\begin{array}{lll}
\underline { \text { Test }}&\underline { \text { Result }}& \underline { \text { Reference range }}& \underline { \text { 1:1 Mix with }}\
&&& \underline { \text { Normal Plasma }}\
\text { Prothrombin time (PT) } & 12 \text { seconds } & 11-15 \text { seconds } \
\text { Partial thromboplastin time } & 57 \text { seconds } & 25-37 \text { seconds } &36 \mathrm{~seconds}\
\text { (PTT) }&&&\text { (immediate) } \
\text { Fibrinogen }& 450 \mathrm{mg} / \mathrm{dL} & 150-400 \mathrm{mg} / \mathrm{dL}
\end{array}$
What would be a reasonable next step to perform?

Question

A 67-year-old woman arrives at the emergency department with acute bleeding into the back of the throat.A coagulation screen is ordered with the following results:
$\begin{array}{lll}
\underline { \text { Test  }}&\underline { \text {  Result }}& \underline { \text { Reference range }}& \underline { \text { 1:1 Mix with }}\
&&& \underline { \text { Normal Plasma }}\
\text { Prothrombin time (PT) } & 12 \text { seconds } & 11-15 \text { seconds } \
\text { Partial thromboplastin time } & 57 \text { seconds } & 25-37 \text { seconds } &36 \mathrm{~seconds}\
\text { (PTT) }&&&\text { (immediate) } \
\text { Fibrinogen }& 450 \mathrm{mg} / \mathrm{dL} & 150-400 \mathrm{mg} / \mathrm{dL}
\end{array}$
What would be a reasonable next step to perform?

Quizplus · Accepted Answer

The normalization of the PTT with a 1:1 mix of normal plasma suggests the presence of a factor deficiency rather than an inhibitor. However, the immediate correction of PTT after mixing suggests that an inhibitor might be present, which can be overcome by the excess factors in the normal plasma. Incubating the 1:1 mix at 37° C for 1 hour and then repeating the PTT can help differentiate between a factor deficiency (where the PTT would remain corrected) and the presence of an inhibitor (where the PTT may prolong again due to the time-dependent action of the inhibitor).

A 67-Year-Old Woman Arrives at the Emergency Department with Acute