What type of study is this?

This is a Cohort Study study (also classified as: Human Clinical Trial).

What question did this study set out to answer?

This study evaluates blood culture contamination rates and associated risk factors in a hospital setting.

February 23, 2026Open Access

Risk factors for blood culture contamination in a tertiary hospital: a one-year retrospective analysis

Key Points

This study evaluates blood culture contamination rates and associated risk factors in a hospital setting.
Retrospective descriptive study of blood culture samples collected over one year.
Evaluated cultures from patients aged ≥ 18 years.
Annaalyzed contamination based on sampling unit, period, and staff collecting cultures.
11.8% of blood cultures were contaminated, with higher rates in internal medicine (12.5%) and ICU (13.5%) compared to surgical wards (3.6%).
Contamination risk was three times higher in internal medicine and 4.1 times higher in ICUs than in surgical wards.
Intern doctors were independently associated with higher contamination risk (OR = 1.68).
Contamination risk increased for cultures taken between July and December (OR = 1.23).

Abstract

Abstract Background Blood culture contamination is a significant problem that can lead to misdiagnosis, unnecessary antibiotic use, and increased workload. This study aimed to determine the blood culture contamination rates in a tertiary hospital and to evaluate the factors associated with contamination. Methods This retrospective descriptive study included blood culture samples collected at a tertiary hospital between January 2023 and December 2023. Cultures from patients aged ≥ 18 years were evaluated. Growth of coagulase-negative staphylococci (CoNS) and other skin flora agents that were not considered clinically significant were classified as contamination. Contamination risk factors, including the sampling unit, sampling period, and healthcare personnel who collected the cultures, were evaluated. Results A total of 7716 blood cultures from 2388 patients were included. 11.8% of the cultures were defined as contaminated. Contamination rates were found to be significantly higher in internal medicine wards (12.5%) and intensive care units (13.5%) compared to surgical wards (3.6%) ( p < 0.001). In logistic regression analysis, the risk of contamination was found to be 3 times higher in blood cultures taken from internal medicine wards and 4.1 times higher in ICUs compared to surgical wards ( p < 0.001 and p < 0.001, respectively). Blood cultures obtained by intern doctors (sixth-year medical students) were independently associated with contamination (OR = 1.68; p < 0.001). The risk of contamination was higher in blood cultures taken between July and December (OR = 1.23; p = 0.004). Conclusion Blood culture contamination is a multifactorial problem influenced by factors such as the sampling unit and staff experience. These findings highlight the need for targeted quality improvement interventions, particularly structured training for newly rotating clinical staff. Clinical trial registration Not applicable.

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