Blood Culture Sampling Practices among Internal Medicine Inpatients

Abstract

Objective: Blood cultures are essential for the diagnosis of bloodstream infections; however, they carry a risk of both low yield and culturing skin contaminants. The optimal culturing threshold which results in a high sensitivity of detecting bacteremia yet has a low contamination rate is not well defined. We sought to analyze the blood culture sampling practices, rates and results among patients admitted under internal medicine. Methods:Retrospective analysis of prospectively collected patient data on over 160,000 patient admissions from July 2008 through end of June 2015 at Tel Aviv Sourasky Medical Centre, a 1440-bed tertiary care teaching hospital in Tel Aviv, Israel.Results: Blood cultures were drawn in 35% of internal medicine admissions. The overall blood culture sampling rate was 168 blood cultures per 1,000 patient days. 70% of episodes of suspected bacteremia occurred during the first 48 hours of admission. 4% of blood cultures yielded a bloodstream infection, while the contamination rate was 3.5%. Single aerobic blood cultures were collected in 35% of episodes of suspected bacteremia, and the BSI rate among these episodes was 5.3%. Conclusions:The hospital practice of blood culture sampling varies predominantly by ward and therefore likely by clinician practice. In an internal medicine patient population where the median age was over 70 years the overall blood culture sampling rate was 168 blood cultures per 1,000 patient days and the incidence of BSI was 4%. Single blood cultures are frequently collected, and approximately half of all positive cultures are due to contaminants.

Evaluation of Quality Assurance Indicators and Contamination Rate in Blood Culture

“…Single blood cultures are often collected during suspected bacteremia events. Guidelines for obtaining blood culture guide clinicians to determine if patient needs blood culture or not and how many cultures they will get from the patient (17). Taking too many sets is not cost effective and not having enough number of sets and the lack of anaerobic or aerobic vials in one set may delay accurate diagnosis.…”

“…In our study, Gram staining and final identification agreement rate was found as 97.55% which is high. Assuming that delays in bacterial isolation and identification in blood cultures increase the mortality rate by 1.2% for each day of delay (17), it is suggested that Gram staining performed with well-trained experienced personnel would be more effective together with molecular methods which are being used more frequently nowadays.…”

Eosinopenia as a diagnostic marker of bloodstream infection in a general internal medicine setting: a cohort study

“…However, the usefulness of this test is limited except in special situations [e.g. inpatients with suspected infectious endocarditis [2] or meningitis [3]] because of its poor sensitivity in ambulatory outpatient [4], primary care, and hospital internal medicine department settings [5]. Additionally, many contaminants may lead to a false positive culture and, consequently, unnecessary therapy [6].…”

Eosinopenia as a diagnostic marker of bloodstream infection in a general internal medicine setting A cohort study

“…However, the usefulness of this test is limited except in special situations [e.g. inpatients with suspected infectious endocarditis(2) or meningitis(3)] because of its poor sensitivity in ambulatory outpatient(4), primary care, and hospital internal medicine department settings (5).…”