OBJECTIVES: Despite manufacturers' claim that systematical assessment of serum indices does not impact on testing efficiency, there is widespread perception that this practice may increase the turnaround time (TAT). A multicenter investigation was planned to verify TAT and performance of serum indices on five different clinical chemistry analyzers. DESIGN AND METHODS: Twenty study samples prepared from pooled sera of outpatients, emergency department, intensive care unit and dialyzed patients were divided in aliquots and shipped to 5 different laboratories. According to local instrumentation (Beckman Coulter AU5800, Roche Cobas 6000, Siemens Dimension Vista 1500, Abbott Architect c 16000 and Ortho Vitros 5.1/FS) and reagents, 13 clinical chemistry parameters were assayed on all study samples, with or without contextual assessment of serum indices. RESULTS: The TAT with assessment of serum indices modestly or even negligibly increased, and varied from -0.2 to +5.0% (i.e., from -3 to +85s). When using the lowest thresholds for sample acceptability, the agreement of hemolysis index (HI) among different instruments was comprised between 0.62 and 1.00 (all p