The purpose of quality control program was to make doctors and laboratory personnel trust in laboratory results and consequently increasing confidence in laboratory achievements. The quality assurance means raising the level of quality in all tests that lead to raising the level of work efficiency and laboratories including minimum expense for society and minimum time for lab personnel. This study aimed to assess and determine the accuracy and precision of results in Tabriz medical diagnostic laboratories. Materials and Methods: In this retrospective study, 790 stool samples were selected randomly and tested by standard methods.Student t- test, SPSS software and sensitivity and accuracy formulas were used for data analysis. Results: The sensitivity was 62%, 22% and 8% with 95% confidence intervals for worm's eggs, protozoan cysts and trophozoite detection respectively. Conclusion: To elevate quality assurance in clinical diagnostic laboratory, monitoring and check of the laboratories by standard methods continually should be done.