Final answer:
The nurse would expect to find a positive Antistreptolysin (ASO) titer to confirm the presence of acute poststreptococcal glomerulonephritis.
Step-by-step explanation:
The diagnostic test that will confirm the presence of acute poststreptococcal glomerulonephritis is C. Antistreptolysin (ASO) titer.
Antistreptolysin (ASO) titer is a blood test that measures the level of antibodies called antistreptolysin O in the blood. Elevated levels of ASO antibodies indicate a recent streptococcal infection. In the case of suspected acute poststreptococcal glomerulonephritis, a positive ASO titer would support the diagnosis.