Investigation of the burden of blood and urine culture contaminations to the microbiology laboratory and sample rejection rates

Errors in the preanalytical process cause the rejection of the samples from the beginning of the test request to the acceptance of the samples in the laboratory. Due to the difficulty of standardization and the fact that a large part of the test errors occur in the pre-analysis process, it is of great importance to eliminate errors in the preanalytic stage. The undesirable effect of the prenatal process in the Microbiology Laboratory is contamination. Contamination leads to cost and time loss in health services, delays the creation of treatment options for patients, and causes time loss for health workers. In our study, the effects of contamination rates in blood and urine cultures on the laboratory were evaluated in terms of cost and time; our sample rejection rates were calculated. In addition, it is aimed to guide the corrective and preventive actions that can be taken to reduce contamination rates. From the data system of our hospital, the total number of samples sent to the Medical Microbiology Laboratory, the number of rejected samples without being evaluated, the number of samples evaluated as blood culture and urine culture contamination were obtained. Differences in results by years, clinics to which samples were sent, and gender were analyzed. January January Dec 1, 2019 – January 1, 2022, a total of 821236 samples were sent to the Medical Microbiology Laboratory of the Faculty of Medicine of the University of Duzce, and 11905 of them (%1,45) were rejected without being evaluated. The most common reason for rejection was determined as an inappropriate sample. A total of 43606 urine culture samples were sent, and 11223 (%25,7) samples resulted in contamination. It was found that the contamination rate in urine culture was higher in women than in men, while in the pediatric emergency department (%38,1) it was higher than in other departments. A total of 13397 blood samples were sent in a menstrual blood culture bottle. Of these patient samples, 916 (%6,8) samples resulted in contamination. It was found that the contamination rate was higher in emergency departments (%9,1) than in other departments. The cost of blood and urine culture samples resulting in contamination has been calculated as a total of 51700 TL. Laboratory employees had to spend 506 hours for contaminated samples. In order to prevent contaminations and sample rejection, it is thought that the "correct sample collection and transfer" trainings, which are carried out with appropriate frequency in our hospital, should be increased in sections with high contamination and rejection rates.