A drug X is secreted through renal tubles,tubular secretion of this drug can be confirmed if renal cleraclea of drug X is

Ref-KDT 6/e p30 Atter filtration from glomerulus, a drug may undergo two processes (tubular reabsorption and tubular secretion) before going out from the body i.e renal clearance. Suppose 100 mg of a drug is filtered by glomerulus and the ren clearance is 150mg,it mean 50mg is coming from somewhere else, i.e. tubular secretion must be present. However,we cannot say that reabsorption is not occuring because if 20 mg is reabsorbed and 70 mg is secreted, same thing can Suppose, 100 mg of a drug is filtered but renal clearance is 50 mg. Therefore, 50 mg must have gone somewhere i.e. tubular reabsorption must be occuring, Again, we cannot say that tubular secretion is not present