What these results support and what they do not

Both cases are supported by the same reasoning: mechanism sets which test is sensitive, INR standardization applies only to the PT/VKA system, a normal screening test does not exclude DOAC or LMWH activity, and a heparin-exposed line can fabricate a heparin-like pattern that resolves on peripheral redraw. None of this recommends a reversal agent, a dose, a specific therapeutic range, or a specific critical value; those decisions are drug-, method-, and policy-specific and belong to local procedure.

Check local reagent sensitivity, reportable range, therapeutic target, and assay availability before you act on this pattern, because each one can change what the same number means: a less-sensitive local reagent can hold PT or aPTT inside the reference interval at a drug level that would flag on a more sensitive reagent, a result above the reportable range needs a dilution or an alternate method before it can be released as a number, a therapeutic target that differs from the one used here changes whether a result reads as subtherapeutic or excessive, and a drug-calibrated assay your laboratory does not perform means the specimen has to be sent out or the question answered a different way, not skipped.

One caveat on method scope: conventional clot-based PT and aPTT and the drug-specific assays named above are covered here; chromogenic PT/aPTT endpoints fall outside the H47 standard referenced here and are not covered. The reference intervals used in the guided cases are illustrative adult values.

When a coagulation result does not fit the clinical picture, name the mechanism you expect, name the test that is actually built to detect it, and check the specimen history before you trust the number. A clean-looking PT or INR is not, by itself, evidence that an anticoagulant effect is absent.