Investigation the ideal timing and the number of blood culture sampling, and the relation between blood culture and fever

Nosocomial (hospital-acquired) bloodstream infections (BSIs) continue to be an important cause of morbidity and mortality for inpatients of intensive care units (ICUs) in our country, as well as all over the world. Today, blood culture is still considered as one of the most important diagnostic tools to identify the etiologic agent and also to confirm the diagnosis of BSI suspected patients.Recent technical advances in blood culture technology have decreased the time to detection of causative microorganisms. However, despite all improvements, it is still reported that blood culture positivity rates are not satisfactory. Therefore, various studies are conducted to ensure more efficient use of the blood culture, which is generally recognised as a very important diagnostic tool.Indications for blood culture are various and have not been standardized yet. Today, the most common indication to obtain a blood specimen for blood culture is the patient's fever. However, some studies have also shown that fever has not correlation with positivity of the blood culture.In this present study, it was aimed to investigate the relationship between the timing and the number of blood sampling for blood culture and fever, furthermore, to determine the current status of antibiotic resistance of the isolated bacteria, so, to assist in establishing empirical treatment protocols for the inpatients, who assumed to have a BSI, in Anesthesia Intensive Care Unit (AICU), Faculty of Medicine, Celal Bayar University.45 patients who were hospitalized in AICU in the period between June 2010 and May 2011 were included in the study. A total of 300 blood cultures sample were taken from patients. The first sample was collected when it was deemed appropriate by the clinician (0. h), and additionally two other samples were collected at the second and fourth hours after the first sample. Fever of the patiens were also recorded simultaneously with the blood sampling.In BSI attacks, bacterial growth was detected in only 39 (39%) of the samples collected at 0. h, while in 49 (49%) and 44 (44%) of the samples, collected at 2h. and 4., respectively. Furthermore, total positivity rate was found to reach 55% for the samples collected at 0. and 2. hours, while 62% for the samples taken at 0., 2., and 4.h.Bacterial growth was detected in 50% of the 90 blood samples collected while fever was rising in 30 BSI attacks, and 53.5% of the 129 samples collected while fever was decreasing in 43 BSI attacks, also in 22.2% of the 81 samples collected in the afebrile periods of the 27 BSI attacks.As a conclusion, detection rate of the causative microorganisms was observed to increase when blood specimens were collected 3 times at 2 hours intervals, as the first sample to be collected when the clinician deems it appropriate. Therefore, blood sample collection at regular intervals, regardless of fever, is thought to be useful in the diagnosis of BSIs. It is also believed that, conducting further studies with larger samplings, and comparing data from these various studies would definitely ensure more effective use of blood culture, which is considered as a very useful diagnostic tool.Key Words: Blood Stream Infection, Blood Culture, Positivity Rate