What do you use as a cut-off point for an aPTT to reflex to a mixing study? Our current policy is to perform a mixing study on every pre-surgical patient with an "elevated" PTT. Elevated = anything above the normal cutoff. So with 36 seconds being our high end of normal, a 36.1 is reflexing a mixing study.

I haven't had much luck finding what other's are doing.....

Yikes! We only do them when they are specifically ordered or a pathologist asks for one.

When they are ordered, we use a cutoff of >45, our reference range is 18-36.

Scott

The Mixing Study is specifically ordered by the doctor and we will perform it if the PTT or Protime is above normal range. ( 36.0 is our cut off for normal PTTs). If the results are normal we order a regular PTT or Protime and note that mixing study was not indicated.

We also only perform if the doctor specifically requests, then any abnormal PTT would get the study.

Trish

We have a cut off at 5.0 seconds above the high normal limit. Look at "The Fritsma Factor" online. It is the best place for Coag questions and you may find yours already answered by gurus in the field.