Final answer:
The diagnostic criteria for IgA vasculitis/HSP involve clinical manifestations and laboratory findings, including purpura, gastrointestinal symptoms, joint pain or swelling, kidney involvement, and increased levels of IgA.
Step-by-step explanation:
Diagnostic criteria for IgA vasculitis, also known as Henoch-Schönlein purpura (HSP), include a combination of clinical manifestations and laboratory findings. The American College of Rheumatology (ACR) has established diagnostic criteria, which include the presence of purpura or petechiae (small red or purple spots on the skin), and at least one of the following: gastrointestinal symptoms (such as abdominal pain, vomiting, or bloody stools), joint pain or swelling, or kidney involvement (such as abnormal urine tests or kidney biopsy findings). Additionally, an increased level of IgA in the blood is often observed. It is important to consult with a healthcare professional for a definitive diagnosis and appropriate management of HSP.