The request that arrives with the specimen

A request lands on the bench: a patient on documented aspirin and clopidogrel needs to know whether the sample shows residual ADP-pathway reactivity before an interventional cardiology team finalizes its plan. The citrate tube in hand is visibly short filled. The companion complete blood count shows a platelet count of 62 x10^9/L, a hemoglobin of 8.1 g/dL, and a leukocyte count of 16.8 x10^9/L, all outside their reference ranges. Blood was drawn two hours after the recorded morning dose.

Before touching an analyzer, confirm that this specimen, in this condition, can answer the question that was actually asked; whether the drug is working is a separate question that comes later. A short-filled citrate tube changes the ratio of anticoagulant to blood, and a platelet count this low can independently blunt or distort an aggregation signal regardless of any drug effect. Releasing a platelet-function result from this draw would answer a question nobody asked and hide the real problem.

A single drug name does not point to a single test; platelet count and routine coagulation screens cannot answer a pharmacodynamic question, and the specimen itself, not the drug, can be the reason for an unexpected result.

A request for a platelet-function answer is also a request to check whether the specimen in hand is capable of producing one.