Abstract
When diagnosing spontaneous bacterial peritonitis (SBP), the low positivity rate of the ascitic fluid culture test is an issue. Studies on the usefulness of the blood culture test in SBP diagnosis have been relatively limited to date. Thus, we conducted a retrospective study to evaluate an appropriate diagnostic method for SBP. We analyzed 59 cases of SBP [22 cases in the group found positive for the causative bacteria by the ascitic fluid culture test (hereafter the ascitic-culture-positive group) and 37 cases in the group found negative for the causative bacteria (hereafter the ascitic-culture-negative group)] treated at our hospital from July 2012 to December 2019. The ascitic-culture-negative group was defined as having an ascitic fluid neutrophil count of 250/μL or more. Blood samples for culture were collected in 72.9% of cases (43/59 cases), all of which were a two-set collection. Among the 43 cases with blood samples collected, 48.8% (21/43 cases) were positive for the causative bacteria in their blood cultures: 70.0% of cases in the ascitic-culture-positive group and 30.4% of cases in the ascitic-culture-negative group were found positive for the causative bacteria by the blood culture test (p < 0.05). Four of the seven cases who were found negative by the ascitic fluid culture test but positive by the blood culture test had been treated with antibiotics before the collection of ascitic fluid for culture. The findings showed that the positivity rate of the blood culture test in SBP was relatively high, even in the ascitic-culture-negative group, suggesting the importance of performing blood culture tests before the administration of antibiotics. In the detection of causative bacteria, this study addresses the role of laboratory technicians in diagnostic stewardship, that is, to inform medical doctors on the appropriate method for taking samples.
