Abstract: Objective In order to have a better understanding of the effects of reacted conditions to PCR results.Method By adjusted the quantities of templates,concentrations of outer primers and outer cycles in one tube nested PCR.We randomly selected the positive and negative samples confirmed by clinical bacteriology and detected samples by PCR.Result (1)It is affected to the PCR results by the quantities of templates and outer cycles in one tube nested PCR.It was pointed out that it was important for the optimized condition of PCR in different laboratories.(2)By using the optimized PCR condition to detect the clinical sputum samples,the PCR results had a high correlation with the positive bacteriological samples(more than 90%).The PCR positive rate was 53% for the negative patients confirmed by bacteriology,and it could be repeated.Conclusion Optimized PCR condition was necessary when PCR as a clinical tool.

Key words: Polymerase chain reaction, M.tuberculosis