Abstract: OBJECTIVE：To investigate involvement of blood collections by time in the combined chronic toxicity and carcinogenicity test for magnesium alloy bone plate，and to provide reference for establishment of the national standard for such tests in the field of medical devices. METHODS：160 SD rats (half males and half females) were randomly assigned to the test and the control groups. The test articles were implanted into the subcutaneous tissues and sham operations were conducted to the control rats. The two groups of animals were anesthetized and blood samples were collected during the 3rd，6th，12th and 18th months for clinical pathology analyses. Hematology and clinical chemistry values were analyzed statistically. RESULTS：Compared to the control animals，there were no significant difference in hematology values and clinical chemistry values. CONCLUSION：It is feasible to cancel the blood collection by time when conducting the combined chronic toxicity and carcinogenicity test on medical devices/biomaterials. At the same time， frequencies of clinical observations could be increased so that the dying animals could be taken blood and dissected in time. This would ensure survival rates of animals and better analyses of chronic toxicity and carcinogenic effects of materials on rats.

Key words: medical devices, combined chronic toxicity and carcinogenicity test, blood collection by time, magnesium alloy materials, bone plate