Proficiency Testing/EQA / 2024 Surveys / Immunology and Flow Cytometry / Immunology Help Please log in to determine if you are eligible to purchase PT Programs. ANTIHISTONE ANTIBODY - AHT Analytes/procedures in bold type are regulated for proficiency testing by the Centers for Medicare & Medicaid Services (CMS). Analyte Challenges per Shipment Number of Shipments Antihistone antibody 3 Two shipments per year Program Information Three 0.5‑mL serum specimens Shipping Schedule Shipment A: February 5 Shipment B: July 1 Guest Log in/Register