MON-314 Development Of The 2ndWorld Health Organization International Standard For Alpha-fetoprotein

Abstract Disclosure: K. Partridge: None. C. Sturgeon: None. E. Atkinson: None. M. Moore: None. P. Rigsby: None. B. Cowper: None. Alpha-fetoprotein (AFP) is a glycoprotein in the serum albumin family, primarily produced in the liver of foetuses during gestation. While AFP levels are normally low in the blood and serum of non-pregnant adults, levels increase during the first and second trimester of pregnancy. Higher than normal levels in pregnancy can also be indicators of birth defects such as anencephaly, omphalocele and spina bifida. Elevated levels in non-pregnant adults can also be indicative of disease, including hepatocellular carcinoma, germ cell tumours, and chronic active hepatitis. Measurement of AFP by immunoassays has therefore become widely established in the diagnosis and monitoring of disease states, responsiveness of patients to therapy, and in Triple and Quad pregnancy screening. Of the many commercially available AFP immunoassays on the market, the majority are traceable to the 1st WHO International Standard for Alpha Fetoprotein (1st WHO IS for AFP, 72/225), where it serves as a tool aimed at harmonisation of AFP immunoassay measurements. Stocks of the 1st WHO IS are now exhausted. Therefore, a replacement WHO IS, coded 22/216, has recently been produced at the MHRA. In this study, we describe the process of developing and characterising the 2nd WHO IS. With support from UKNEQAS, via an International Collaborative Study, we (i) evaluated the suitability of a highly purified preparation of AFP from human cord serum to serve as the 2nd WHO IS, (ii) value assigned the candidate standard, in international units (IU), in terms of the 1st WHO IS, by immunoassay, (iii) assessed commutability of the candidate standard with clinical samples in major commercial assays and (iv) evaluated long term stability of 22/216 by accelerated thermal degradation analysis. 20 different immunoassay platforms were used, including both manual and automated ELISA methods. Data from the study demonstrated good parallelism for the candidate IS, relative to the 1st WHO IS, indicating the candidate IS behaves in a similar manner to the current IS, allowing for the overall geometric mean potency value to be assigned as 7756 IU/ampoule (inter-lab GCV 8.73%). Commutability of candidate IS preparations with clinical samples was mixed, but comparable to those shown for the 1st WHO IS, 72/225, using a “calibration effectiveness” approach. Finally, accelerated thermal degradation samples were tested by immunoassay. Data indicated that 22/216 showed good stability with an estimated loss in potency of 0.07% per year when stored at -20°C Taken together, the data supports the introduction of 22/216 as the replacement IS for AFP, to continue to aid harmonisation of AFP immunoassays. 22/216 was established as the 2nd WHO IS by the WHOs Expert Committee on Biological Standardisation (ECBS), and replaces the 1st WHO IS, 72/225. Presentation: Monday, July 14, 2025