External quality assessment of assays for hormones and tumor markers in Italian laboratories.

External quality assessment (EQA) programs run by CNR/Tecnostandard for immunoassays of hormones and tumor markers, started in 1980, presently include as many as 20 analytes; about 300 laboratories are involved in these programs. For all immunoassays submitted to the EQA, the inspection of cumulative results allows the current situation to be documented for total variability and its within-kit and between-kit components (the former accounting for the reproducibility and robustness of the kits and the latter for their systematic differences of estimation). For 13 assays subjected to EQA for longer, the variability trends over time are depicted, and single factors affecting the overall quality of particular assays are identified. Among these, experimental simplification of kit structure, alignment of calibrators with an acknowledged reference material, and adoption of monoclonal-antibody based two-sites assays can be mentioned. On the contrary, neither automation of the procedures nor (more expectedly) increasing use of nonisotopic techniques has proved effective in significantly improving the analytical quality.