APTT Mixing Study

1
APTT Mixing Study

• The APTT Mixing Study is used to ascertain
  whether a prolonged APTT is due to a factor
  deficiency or to the effect of an inhibitor.
  Below are some challenges for performing and
  interpreting results
• APTT of Normal Pooled Plasma NPP used to make
  the mix must fall within your laboratorys
  reference range. The NPP should be prepared from
  gt20 normal donors to statistically allow for 100
  activity of all factors.
• Mixtures can be of any combination though the
  50/50 mix is most widely used. A mix using 1
  part NPP 4 parts patient may be used to detect
  effects of weak inhibitors on the NPP.
• Testing can be performed in two manners
  immediately upon mixing and after incubation at
  37 oC for 2 hours. If one incubates the 50/50
  mix, then one also needs to run a mixture (100
  Patient and 100 NPP separately incubated and
  then mixed AFTER 2hours at 37 oC) to serve as a
  control for FV FVIII lability.

Lab Pointer
M Ledford-Kraemer
Revised mmiii
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