What diagnostic tests are commonly performed to confirm acute poststreptococcal glomerulonephritis (APSGN) in adolescents?

The confirmation of acute poststreptococcal glomerulonephritis (APSGN), particularly in adolescents, relies on specific diagnostic tests that provide insight into kidney function and the inflammatory response to a prior streptococcal infection. The measurement of serum complement (C3) activity level is critical because, in APSGN, levels of complement, particularly C3, are often low due to consumption during the immune response to the streptococcal infection. Additionally, a urinalysis is essential since it reveals key indicators such as hematuria, proteinuria, and the presence of red blood cell casts, all of which are characteristic of glomerulonephritis.

This combination of serum complement testing and urinalysis effectively highlights the kidney's response to the condition, confirming the diagnosis of APSGN. The understanding of these tests and their implications is crucial for determining the appropriate management and monitoring of adolescents diagnosed with this condition.