OBJECTIVE To explore the optimal preprocessing protocols for colonoscopes based on the orthogonal experimental design combined with cost analysis.

METHODS An orthogonal design experiment was conducted in Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical Hospital. Totally 4 influencing factors for preprocessing and 3 corresponding levels were formed to 9 types of preprocessing protocols on the bases of orthogonal design. The colonoscopes that were used for diagnosis and treatment of 180 patients were randomly divided into 9 groups, each group was treated with one preprocessing protocol. The adenosine triphosphatase (ATP) test and microbial culture were carried out after the preprocessing, cleaning and disinfection. The costs of the 9 preprocessing protocols were analyzed.

RESULTS There were significant differences in the ATP value and bacterial colony counts between the factor A (the type of preprocessing solution) and the factor C (preprocessing suction time) after the preprocessing (all P < 0.05); A3 and C2 were the optimal levels. There were no significant differences in the ATP value and bacterial colony counts among the factor A (the type of preprocessing solution), the factor B (the change frequency of preprocessing solution), the factor C (the preprocessing suction time) and the factor D (the interval between preprocessing and the cleaning). The qualified rates of cleaning of all the 9 groups reached up to 100.00%, and the qualified rates of disinfection were no less than 90.00%. The result of rank sum test showed that there were no significant differences in the ATP value (H=5.449, P=0.709) and the bacterial colony counts (H=1.770, P=0.987) among the 9 groups after the disinfection. The cost analysis showed that the cost was lowest when water was used as the preprocessing solution.

CONCLUSION The optimal protocol for preprocessing of colonoscopes is that the alkaline solution is used as the preprocessing solution, with the change frequency changing every 4 hours, the suction time 20 seconds; the delay time should be determined based on the specific clinical condition, and the colonoscopes should be cleaned as early as possible.