Background: The different scoring methods used by eight European External Quality Assessment Schemes

(EQASs) for occupational and environmental laboratory medicine were compared to develop suitable quality specifications as a step toward harmonization. Methods: Real results for blood lead and serum alumi-num assays, reported by participants in Italian and United Kingdom EQASs, were evaluated according to individual scheme scoring criteria. The same results were then used to produce z scores using scheme-based between-laboratory SDs as the estimate of variability to determine whether simple performance-derived quality specifications produced better agreement among schemes. Results: The schemes gave conflicting assessments of participants ’ performance, and participants judged to be successful by one scheme could be defined as perform