Abstract: AIM: To study the qualitative methods for analyzing laboratory variables from multi-center clinical trial.METHODS: Two methods were proposed.One is to compare the proportions of persons whose values are clinical abnormal after treatment but normal before treatment.The other is to test the randomness of the difference of the values before and after treatment.RESULTS: Both of the methods can eliminate the difference between centers , as well as the difference between age groups and gender.The likelihood ratio test or Fisher's exact probability method should be used for first method , and u test or exact method based on binomial distribution with rate 0.5 for second method.CONCLUSION: In multi-center clinical trial , both qualitative and quantitative methods should be used for laboratory variables to evaluate the safety and tolerability of the drug being tested.

Key words: multi-center clinical trial, laboratory data, qualitative analysis, likelihood ratio test, exact method