For cell counts and biochemistry tests, various body fluids are analyzed, primarily Cerebrospinal Fluid (CSF), Pleural Fluid (lungs), Peritoneal Fluid/Ascitic Fluid (abdomen), Synovial Fluid (joints), and Pericardial Fluid, to check for inflammation, infection, or malignancy, measuring cells, protein, glucose, LDH, etc., with collection via needle aspiration (paracentesis/thoracentesis) or lumbar puncture