What's the most specific urinary finding in acute pyelonrphritis sir?

What’s the most specific urinary finding in acute pyelonrphritis sir?
Some books it’s given as wbc cast and others, nitrite test?
Sir can you clarify what’s the correct answer.

Nitrite test would be positive in UTI also right.

Acute pyelonephritis means renal parenchymal involvement; so WBC casts should be better answer.

WBC casts