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study on the rate of blood culture contamination in emergency department, Hospital Universiti Sains Malaysia
Blood culture is a vital investigation with major implication for the diagnosis of serious infection and selection of appropriate anti-microbial therapy. A positive blood culture can be the first step in reaching the definitive diagnosis in a patient with presumed sepsis. Unfortunately, false positives can occur due to contamination. As such, the onus is on the nursing and medical staffs to be responsible for the safe and effective blood sampling, especially in an ED setting, where accurate blood sampling result can have a critical, imperative impact on the direction on patient management. Blood culture contamination is defined as the growth of bacteria in the blood culture bottle that is not present in the patients blood. It is a common phenomenon. While target rates for contamination have been set at 2 to 3%, in reality, the rate of blood culture contamination varies between departments and hospitals. In UK, souvenir et al reveals that contamination of blood cultures is a common problem with contamination rates varying between 2% and more than 6%. In the emergency department of Hospital Universiti Sains Malaysia (HUSM), the annual positive blood culture rates fluctuated between 9.5-40.8%. Out of these, contaminated samples account for 2.7-14.3% of all positive cultures. Most of these false positive results were caused by endogenous human microbial flora. As a result, strict skin preparation and good venepuncture technique are important determinants in reducing the rate of contamination. This is cross- sectional study. All blood culture samplings who meet the inclusion criteria (and not meeting any exclusion criteria) were collected by various health care professional in ED HUSM. Patients venous bloods were obtained according to their current practice of blood culture sampling. The person who obtains the blood culture will fill up the study document. For each month, the total number of cultures yielding organisms considered being contaminants (from a predefined list) and the total numbers of blood culture sets taken were reviewed by researcher via patients record in Microbiology and Parasitology lab, HUSM. To control for the continued isolation of significant bacteraemia, the number of Gram-negative organisms isolated will also be collected. Each blood culture was processed according to the recommendations of the Clinical and Laboratory Standard Institute (CLSI). The registrar in charge will determine which health care group to perform the blood culture task based on table of randomization provided to them.A total of 136 patients were recruited for this study. Mean age of the patient was 57.097±18.63, 50.7% were male and 49.3% were female. From 136 cultures obtained, 44 (32.4%) cultures were positive, while the other 92 (67.6%) samples were negative. Out of these 44 positive cultures, 27 samples were contaminated while 17 samples were non-contaminated. Therefore, the prevalence of blood culture contamination in the study population was 17 out of 136, which was 19.9%. Males, patients aged 50 to 69 years old and source of infection from genito-urinary tract had more contamination as compared to the others from the same variable category. However, these findings were not significant with p-value >0.05 and 95% CI included 1. Among the working days, Friday had the highest prevalence of contamination (36.8%). However, it was statistically not significant with p-value = 0.061. The same finding was noted for variable weekend (p-value = 0.074) and patients triage as semi-critical (p-value = 0.050). Blood samples taken during night shift had 4 times more likely to be contaminated when compared to those taken during morning shift and this finding was significant with p-value = 0.011. No significant difference was noted for samples taken during PM shift. The was no significant association between blood sample contamination with the designation of the person taking the blood culture, years of service, persons teaching place for blood culture taking and whether the person was given proper teaching regarding blood culture taking before (p-value >0.05). As a conclusion, this study has been able to fulfil the objectives set forth at the start. Its shown that the blood culture contamination was far above the targeted rate. We had identified a few factors contributed to the contamination rate in ED HUSM such as working shift, patients age and source of infection. Although these factors were statistically not significance, we hope that this can initiate future study for better understanding regarding blood culture contamination.
1. Introduction -- 2. Literature review -- 3. Research questions/ objective/ hypothesis -- 4. Research methodology -- 5. Result -- 6. Discussion -- 7. Limitations of study -- 8. Recommendations -- 9. Conclusions
Thesis (Degree of Master Of Medicine) - Universiti Sains Malaysia, 2014
Includes bibliographical references (leaves 110-118)