A prolonged screen lands on your bench

A dRVVT screen comes back at 62.0 seconds against a local range of 30.0 to 44.0 seconds. The routine aPTT on the same specimen is also prolonged, at 48.2 seconds against a 25.0 to 35.0 second range. The specimen looks fine: platelet-poor plasma, no clot, no hemolysis, collected and processed on time. The medication review shows no anticoagulant reported. Nothing about the tube explains the prolongation.

The screen is abnormal. The question is whether this pattern demonstrates phospholipid-dependent inhibition, the laboratory signature of a lupus anticoagulant (LA), and whether anticoagulants and other confounders have been ruled out before that call is made. A prolonged screen by itself answers neither question.

LA is an in-vitro phospholipid-dependent inhibitor pattern. It is not, by itself, a diagnosis of antiphospholipid syndrome (APS). That distinction matters for every sentence you write in a report.

A single prolonged clotting time is a starting observation, not a laboratory finding, and it does not by itself justify naming an inhibitor.