These authors attempted to assess platelet function in citrated whole blood by determining the platelet aggregates formed following electromagnetic agitation for 15 minutes.

But then it seems to me it would make more sense if one intended to throw out the iron-contaminated citrated water and replace it with new water, which I realize is expensive.

Typically fibrinogen is measured in citrated plasma samples in the laboratory, however the analysis of whole blood samples by use of thrombelastometry (platelet function is inhibited with cytochalasin D) is also possible.