is the subquery in the following query correlated or uncorrelated? if correlated, which reference causes the query to be correlated?

SELECT DISTANCT PATIENTDIM.PATIENID
FROM PATIENTDIM
WHERE NOT EXISTS
(SELECT 1
FROM ENCOUNTERFACT
WHERE
PatientDim.DurableKey = EncounterFact.patientDurableKey
and encounterFact.type = 'new'