|Year : 2020 | Volume
| Issue : 1 | Page : 7-13
A prospective study on the comparison of contamination rate and risk factors of blood culture done in the emergency department and medical high-dependency unit/medicine intensive care units
Pranav Kumar1, Darpanarayan Hazra2, Ankita Chowdary Nekkanti2, Mamta Madhiyazhagan2, Thomas Sundarshanam3, Veera Raghavan Balaji4, Kundavaram Paul Prabhakar Abhilash2
1 Department of Emergency Medicine, NRI Academy of Medical Sciences, College of Mangalagiri, Guntur, Andhra Pradesh, India
2 Department of Emergency Medicine, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
3 Department of Critical Care, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
4 Department of Microbiology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
|Date of Submission||06-Nov-2019|
|Date of Decision||21-Dec-2019|
|Date of Acceptance||25-Dec-2019|
|Date of Web Publication||03-Feb-2020|
Dr. Darpanarayan Hazra
Department of Emergency Medicine, CMC, Vellore - 632 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Background: Blood culture (BC) is an important tool and also considered the “gold standard” for the diagnosis of bacteremia. Emergency departments (EDs) and medical high-dependency units/medicine intensive care units (MHDUs/MICUs) are particularly susceptible to contaminated BCs due to high staff turnover. However, the need to collect cultures in critically ill patients is essential before the first dose of antibiotics.
Aim: This study aimed to calculate the rate and risk factors of contamination of BC in ED and MHDU/MICU.
Materials and Methods: This is a 2-month prospective observational study with a total of 998 patients – 570 in ED and 428 in MHDU/MICUs. The primary investigator collected the data, and culture reports were followed up to 7 days. Categorical variables were presented as percentages, and quantitative variables were summarized using mean and standard deviation.
Results: The mean age of the population in the ED culture arm was 51 years and in the MHDU/MICU was 46 years. There was a male predominance of 61%. From ED, the most common admission diagnosis was acute undifferentiated febrile illness accounting to 23% of total patients. Lung pathologies were the most common MHDU/MICU admission diagnosis encountered in the study comprising 193 (19.3%) cases. The most common site for culture in ED was the brachial vein (81%) followed by the dorsum of the hand (14%). The most common contaminant was coagulase-negative Staphylococcus (CoNS) with 26 cases, of which 16 were from MHDU/MICU. A total of 48 cases (4.8%) were contaminated in the study, of which 25 (4.4%) cases were from ED and 23 (5.4%) from MHDU/MICU.
Conclusions: BC contamination is a common clinical problem and often leads to adverse impacts on both health care and costs. It is challenging to prevent contamination because of inadequate inpatient capacity, high severity of illness, the rapid turnover of staff, and the high workload and overcrowding.
Keywords: Blood culture, blood culture in emergency department, blood culture in medical high-dependency unit/medicine intensive care unit, coagulase-negative Staphylococcus, contamination of blood culture
|How to cite this article:|
Kumar P, Hazra D, Nekkanti AC, Madhiyazhagan M, Sundarshanam T, Balaji VR, Abhilash KP. A prospective study on the comparison of contamination rate and risk factors of blood culture done in the emergency department and medical high-dependency unit/medicine intensive care units. Curr Med Issues 2020;18:7-13
|How to cite this URL:|
Kumar P, Hazra D, Nekkanti AC, Madhiyazhagan M, Sundarshanam T, Balaji VR, Abhilash KP. A prospective study on the comparison of contamination rate and risk factors of blood culture done in the emergency department and medical high-dependency unit/medicine intensive care units. Curr Med Issues [serial online] 2020 [cited 2022 May 25];18:7-13. Available from: https://www.cmijournal.org/text.asp?2020/18/1/7/277529
| Introduction|| |
Blood cultures (BCs) are considered as the “gold standard” for the diagnosis of bacteremia. Emergency departments (EDs) and medical high-dependency units/medicine intensive care units (MHDUs/MICUs) are areas particularly susceptible to a high burden of contaminated BCs due to high staff turnover and overcrowding. However, the need to collect BC in critically ill patients before resuscitation is essential before the first dose of antibiotics.
A positive BC can suggest a definitive diagnosis, while false-positive results because of contamination can limit the utility of this important tool., False-positive results are seen when organisms that are not actually present in blood grow in the culture.
Contaminated cultures have been recognized as a troublesome issue for decades and continue to be a source of frustration for clinical and laboratory personnel alike. These samples can also increase the laboratory workload and can delay or cause incorrect changes to patient management. This can prolong patient hospitalization, increase the risk of harm, and increase cost to health boards. Current guidelines state that a BC contamination (BCC) rate of 2%–3% is acceptable.,
Faced with a positive BC result, clinicians must determine whether the organism represents a clinically significant infection associated with the risk of morbidity and mortality or a false-positive result of no clinical consequence. The main objective of this study was to calculate the most common contaminant, rate and risk factors of contamination of BC in ED and MHDU/MICU.
| Materials and Methods|| |
This is a prospective, observational study comparing the BCC rate and risk factors in ED and MHDU/MICU.
The present study was conducted in the ED and MHDU/MICU of the Christian Medical College Hospital, Vellore, India, which is a tertiary medical care center. The ED is a 49-bed department and tends to about 300 patients per day, including infective and noninfective patients. MHDU/MICUs have 12 beds each, and they receive patients directly from the ED or medical wards through an open admitting system.
Duration of study
The study was conducted for a period of 2 months from January 1, 2019 to February 28, 2019.
All patients with features of bacteremia/fever or any infectious condition who underwent BC in the ED and in the MHDU/MICU were recruited. Data with respect to culture methodology were collected from the ED department and MICU/MHDU.
Data of the patients were obtained from the electronic hospital records, and the details of history and physical examination findings of all patients were recorded on a standard data collection sheet. The following were extracted: age/sex, indication for BCs, comorbidities (diabetes mellitus, hypertension, chronic kidney disease, chronic obstructive pulmonary disease, HIV status, chronic liver disease, and cerebrovascular accident), site of BC, and admission diagnosis.
Site from where blood drawn resulting in the least contamination.
The inclusion criteria were as follows:
- Patients with BCs taken in the ED
- Patients with BCs taken in MHDU/MICU
- Patients above the age of 18
- Patients consenting to participate in the study.
The exclusion criteria were as follows:
- Patients below the age of 18
- Patients not consenting to participate in the study
- Cultures transferred to the laboratory after 12 h.
Consecutive patients who had undergone BC during the study period were recruited in ED and MHDU/MICU to avoid selection bias.
The information regarding the insertion of the line was obtained by direct questioning the physician/technician/staff within 24 h of the procedure to minimize the risk of recall bias.
To minimize the interviewer bias, a standard set of questions were asked according to those prepared in the clinical research form in advance.
A study conducted by Raja NS, O'Neill B. (2017) demonstrated a contamination rate of 31% in MICU/MHDU and 20% in ED. Considering a 10% difference in contamination rate, we needed a sample size of 361 from each department. Considering the inadequacy of samples and other unforeseen factors, 10% of extra sample was taken, making a total of 570 in ED and 428 in MICU/MHDU.
All categorical variables were expressed as frequencies and percentages. The data were extracted from the ED triage software and Clinical Workstation and entered into the Statistical Package for the Social Sciences (IBM Corp. Released 2018. IBM SPSS, Version 126.96.36.199, Armonk, NY, USA). Data were summarized using mean with standard deviation for continuous variables and frequencies with percentages.
This study was approved by the Institutional Review Board before the commencement of the study, and approval from the Institutional Review Board Ethical Committee was obtained (IRB Min no: 11301 dated May 24, 2019). Patients were recruited after obtaining an informed written consent. Patient confidentiality was maintained using unique identifiers and by password-protected data entry software with restricted users.
| Results|| |
A total of 998 cases were included in the study, of which 570 were from the ED and 428 were from MICU/MHDU [Figure 1].
The mean age of the population in the ED arm was 51 years and in the MHDU/MICU was 46 years. There was a male predominance in both arms accounting to 609 (61%) of total patients. The most common comorbidity in this study population was diabetes mellitus comprising 209 (36.7%) patients in ED and 130 (30.4%) patients in MHDU/MICU. This was followed by essential hypertension comprising 186 (32.6%) patients in ED and 133 (31.1%) patients in MHDU/MICU. Other comorbidities included chronic kidney disease, chronic liver disease, malignancy, and immunocompromised hosts [Table 1].
MICU/MHDU receives patients directly from the ED and from medical wards through an open admitting system. Lung infection/lung pathology was the most common admission diagnosis in MICU/MHDU, comprising 193 (19.3%) cases. However, in ED, the most common admission diagnosis was acute undifferentiated febrile illness comprising 133 (23%) of total ED cases. Other admission diagnosis included neuroleptic malignant syndrome, diphtheria infection, G6PD deficiency, postrenal transplant, nephrotic syndrome, polymyositis, liver abscess, cardiac pathology, acute abdomen, and autoimmune diseases [Table 2].
Site of culture and contamination rate
The most common site of BC in ED and MICU/MHDU was brachial with 465 (81%) and 129 (30.1%) cultures, respectively. The most common site for contamination in ED was from the femoral (22.2%), and the least common site of contamination was from the dorsum of the hand (1.28%), whereas in MICU/MHDU, the most common site of contamination was from the brachial (6.20%), and the least common was from the arterial line (4.16%) [Table 3].
Procedure related characteristics
In our observational study, it was found that there was no scrubbing of hands before the procedure in ED, whereas it was noted in 265 (61.9%) procedures done in MICU/MHDU. The gloves were worn in a sterile manner in 519 (91.1%) cases in ED, and overcrowding during venipuncture was found in 200 (35.1%) cases. The antiseptic used in ED was chlorhexidine in 115 (20%) cases and betadine in 455 (80%), whereas chlorhexidine was used for all cases in MICU/MHDU. In ED, the antiseptic was allowed to dry in only 32 cases.
The special instrument kit for BC was used for 443 (77.7%) cases in ED and 218 (51%) cases in MICU/MHDU. In ED, the volume of blood collected was 5 cc in 197 (35%) cases and 10 cc in 364 (64%) of cases, whereas in MICU/MHDU, 10 cc volume was collected from 420 (98%) patients. The BC was done in the first attempt in 519 (91%) and 394 (92%) cases in ED and MICU/MHDU, respectively. In ED, majority of the BC samples were collected by emergency medicine technicians, i.e., 543 (95%) cases, followed by 16 (3%) by medical interns and 10 (1.8%) by registrars, whereas in MICU/MHDU, most of the cultures were taken by 382 registrars (89%) [Table 4].
|Table 4: Procedure variables in the emergency department and medical high-dependency unit/medicine intensive care unit|
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Of total 998 study patients, 807 (81%) showed no growth, of which 462 cases are in ED and 345 cases were from MICU/MHDU. The most common contaminant was coagulase-negative Staphylococcus (CoNS) (26), of which 16 patients were from MICU/MHDU [Table 5]. A total of 48 cases (4.8%) were contaminated in the study, of which 25 (4.4%) cases were from ED and 23 (5.4%) from MICU/MHDU.
| Discussion|| |
BC is specimens submitted for the culture of microorganisms. It enables the recovery of potential pathogens from patients suspected of having bacteremia or fungemia. BCC refers to a microorganism isolated from a BC that was introduced during specimen collection or processing and is not considered responsible for bloodstream infection (i.e., the isolates were not present in the patient's blood when the blood was sampled for culture). This was a prospective observational study comparing the contamination rate and risk factors of BCC in ED and MHDU/MICUs.
In our study, any organism growth was seen in 191/998 (19.1%) cases, of which 108 (18.9%) were in ED and 83 (19.4%) in MHDU/MICU. Higher number of growth were noted in ED probably due to the fact that there were a higher number of patients in this arm. CoNS were the most commonly isolated contaminants (26 cases) seen in BC; however, this organism can also be seen in true bloodstream infections. This differentiation has practical importance because of its therapeutic implications as it can prevent injudicious use of antibiotics and emergence of antimicrobial resistance. More importantly, the inability to ascertain and treat true bacteremia can prove costly to the patient, more so if the patient is critically ill or immunocompromised. A clue to the significance of CoNS-positive BC is the number of positive cultures, thus more the number of positive cultures, higher the chances of it being true bacteremia [Table 5]. However, this is not possible when only a single culture sample is obtained before starting the patient on antimicrobial agents. Quantitative BCs (QBCs) can aid interpretation.,, QBCs are cumbersome and not very feasible. On the other hand, the time-to-positivity (TTP) of BCs after loading in the automated systems like BacT/Alert may be a useful surrogate test for bacterial density and interpretation of the significance of CoNS isolated from positive BCs. Similar results were observed in a study by Ramirez et al., who reported a higher BCC rate in ICU (31%) when compared to ED (20%). However, on the contrary, similar type of study by Choi et al. conducted in Singapore showed higher BCC rates in ED comprising 4% when compared to medical wards (0.5%). According to a study conducted by Lee et al. in Taiwan, there was a strong correlation between BCC rates and the degrees of ED crowding (P = 0.001); however, there was no such significance noted in our study population.
In our study, both chlorhexidine and betadine were used for cleaning the site before the procedure. A study conducted by Story-Roller and Weinstein suggests that iodine tincture and chlorhexidine are equivalent antiseptic agents for skin antisepsis in patients who require BCs. Other studies on antiseptic usage and BCC rate showed no significant difference.,,
Various studies have been done to reduce the BCC rate in ED and MICU/MHDU by the use of disinfectants, educational interventions, sampling from separate venipuncture sites, appropriate preparation of culture bottles, the use of the double-needle technique, reliance on a well-trained phlebotomy team, and the use of commercial culture kits. Others include standardizing work processes based on updated policy and procedures, conducting regular audits, and sending feedback.,,,, However, such studies are lacking in an Indian setup; hence, we conducted a prospective observational study comparing the contamination rate and risk factors of BCC in ED and MHDU/MICUs. After reviewing various research articles and through our study, we hereby suggest a checklist to decrease BCC rates in ED and MICU/MHDU [Table 6].,,,
| Conclusions|| |
BCC is a widespread and often frustrating problem seen in all hospitals. We studied the process of BC collection and found inconsistent methods for culture collection with frequent breaches in aseptic technique. Although not significant, there was a lower contamination rate seen among BCs collected in the adult ED at our hospital when compared to MHDU/MICU. Strategies, including the use of disinfectants, educational interventions, sampling from separate venipuncture sites, appropriate preparation of culture bottles, reliance on a well-trained ED/MICU/MHDU technician team, and the use of commercial culture kits, should be followed to decrease the rates of BCC.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
Research Quality and Ethics Statement
The authors of this manuscript declare that this scientific work complies with reporting quality, formatting and reproducibility guidelines set forth by the EQUATOR Network. The authors also attest that this clinical investigation was determined to require Institutional Review Board / Ethics Committee review, and the corresponding protocol / approval number is IRB Min no: 11301 dated 24th May 2019. We also certify that we have not plagiarized the contents in this submission and have done a Plagiarism Check.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]