original_query: What is the purpose of the DHR 123 test?
query: What is the purpose of the DHR 123 test in diagnosing Chronic Granulomatous Disease?
answer: The DHR 123 test measures the respiratory burst of neutrophils stimulated with PMA, showing a shift in fluorescence to rhodamine 123 if the burst is normal.  It's used to diagnose Chronic Granulomatous Disease (CGD), differentiating between X-linked and autosomal forms, detecting carriers, and assessing the severity of the disease.