Evaluation of clinical chemistry using diluted sera in mice and rats

BACKGROUND: In preclinical toxicity and efficacy studies, clinical pathology tests play a critical role in detecting pathological alterations, assessing drug effectiveness, and monitoring animal conditions. However, their application is frequently restricted by the limited sample volumes that can be collected from laboratory animals such as mice and young animals. To overcoming this limitation, dilution of samples may be utilized. In this study, we investigated the impact of pre-dilution by using a Toshiba analyzer and saline as the diluent, comparing analytical results from diluted and undiluted specimens in both mice and rats. Seventeen biochemical analytes were assessed in serum samples diluted 2.5-, 5-, 7.5-, and 10-fold, and these results were compared with those of undiluted samples. RESULTS: We evaluated mean values, bias, two standard deviations (2SD), and the standard deviation index (SDI). To ensure data obtained from diluted samples are valid and dependable, we applied allowable total error (TEa), defined as the maximum acceptable error for a test result to remain reliable and clinically relevant. The mean values from 2.5-fold diluted samples exhibited no significant difference compared to those from undiluted samples in mice and rats, except Cl, Na, ALB, and TBIL. Furthermore, findings from bias, 2SD, SDI, and TEa analyses indicated that a 2.5-fold sample dilution is suitable for clinical chemistry analysis of multiple analytes, except for Cl, Na, and TBIL in both species. CONCLUSIONS: Collectively, these results may serve as a reference for the suitability of diluted serum samples in clinical chemistry analysis. Further studies utilizing various analytical instruments, diluents, or animal species are recommended.