The main factor when considering whether a procedure is diagnostic or therapeutic is to determine the objective of the procedure. If the main objective is to establish a diagnosis for the patient prior to starting any kind of treatment, then it is considered to be a diagnostic procedure. If a diagnosis is already established and a procedure is completed in order to eradicate a problem, then it is considered to be a therapeutic procedure. For drainage root operations, the ICD-10-PCS guidelines state that if a diagnostic procedure is followed by a more definitive procedure (therapeutic) then both the diagnostic and more definitive treatment are coded.