Background
Blood cultures are widely used to diagnose systemic infections and are routinely obtained in clinical practice. Despite meticulous sanitization and handling protocols, blood culture contamination (BCC) may still occur due to environmental and patient-related factors or human error. Reference Doern, Carroll and Diekema1 BCC can lead to unnecessary antibiotic use and prolonged hospitalization, which further leads to patient harm and excess costs. Reference Skoglund, Dempsey, Chen and Garey2 To minimize these consequences, the Clinical and Laboratory Standards Institute (CLSI) has recently set a 1% BCC goal for the US. 3
In the last decade, efforts to achieve this CLSI goal have included the growing use of initial specimen diverting techniques (ISDTs). Reference Patton and Schmitt4 There are three primary ISDTs: two commercial options (Steripath and Kurin Lock) and one manual approach (open ISDT). Reference Al Mohajer and Lasco5 The Steripath and Kurin Lock are both prepackaged collection devices that divert the first 1–2 mL and 0.15 mL, respectively, of blood into a separate chamber before the remainder is collected into culture bottles. Reference Arenas, Boseman, Coppin, Lukey, Jinadatha and Navarathna6 Open ISDT involves manually discarding the first 1–2 mL of blood into a separate container before connecting blood culture bottles for collection. Reference Lalezari, Cohen and Svinik7 A previous review of the existing literature found that adopting ISDTs could achieve the CSLI goal. However, heterogeneity in study design and outcomes has limited direct comparisons between ISDT types or against non-diversion approaches. Reference Al Mohajer and Lasco5
Building on that review, our previous single-center study specifically evaluated the impact of a commercial ISDT (Steripath) compared to no diversion. We found a significant reduction in BCC rates with Steripath. However, there was no observed impact on hospital length of stay (LOS), antimicrobial days of therapy (DOT), or false-positive central line-associated bloodstream infections due to skin contaminants. Reference Febres-Aldana, Ashley and Amenta8
The present study extends that work by assessing the impact of transitioning from the commercial ISDT to the open ISDT method. We aimed to evaluate whether the open approach can maintain the same clinical and patient-care benefits while potentially offering a more cost-effective alternative.
Methods
This was a prospective, non-randomized controlled study conducted at three medical centers in Texas (01/2022–12/2023). Randomization was not feasible because blood culture collection practices needed to be standardized at the institutional level. Two centers comprised the control arm and used the open ISDT throughout the study period. One center comprised the treatment arm and used the commercial ISDT in the preintervention period (01/2022–05/2023), then transitioned to the open ISDT in the postintervention period (05/2023–12/2023). All nurses and laboratory personnel responsible for blood culture collection received standardized training in both techniques. To ensure adherence to the respective techniques, culture samples were required to be submitted with either the Steripath packaging wrap or a red top tube showing evidence of diversion (open ISDT arm). We included adult patients with ≥1 set of blood cultures collected on presentation to the emergency department or at hospital admission; only index blood cultures—those obtained at the start of the hospital encounter—were included in the analysis. We did not exclude patients based on emergent line placement, prior antibiotic exposure, or other clinical characteristics to reflect real-world practice, which may contribute to clinical heterogeneity.
The primary outcome of this study was the BCC rate, defined as the proportion of included encounters with ≥1 contaminated index blood culture set among all included encounters with index blood cultures. Contaminants were classified using Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) criteria for common commensals, with prespecified organism exceptions and time-window rules to differentiate contaminants from true bacteremia (Supplemental Table S1). 11 Secondary outcomes examined included hospital LOS, antibiotic days of therapy (DOT) involving vancomycin or daptomycin, and laboratory-associated costs. Cost analysis incorporated material and labor expenses incurred by the hospital for blood culture collection, plating, staining, speciation, and susceptibility testing, and was confirmed with hospital administration. Downstream costs of contamination (e.g., antibiotic exposure, procedures, or incremental LOS) were outside the scope of this analysis.
Outcomes were evaluated using multivariate regression models: logistic regression for BCC, linear regression for log-transformed LOS and laboratory costs, and zero-inflated negative binomial regression for DOT given overdispersion and excess zeros. Covariates were selected a priori based on clinical relevance and availability and included age, sex, race, SARS-CoV-2 status, transplant status, and admission/collection location category. A difference-in-differences (DID) approach evaluated changes over time between the treatment and control arms (Figure 1); the Treated × Time interaction term captured the estimated intervention effect. The DID approach assumes parallel preintervention outcome trends; we assessed this visually using monthly outcome plots (Figure 1) and additionally tested for differential preintervention trends in monthly BCC rates, which showed no evidence of differing slopes (treated × month interaction P = .955). Statistical analysis was performed using R version 4.2.2 (The R Foundation for Statistical Computing, Vienna, Austria). The study was approved by the Institutional Review Board.
Difference-in-difference (DID) plots for study outcomes. This Figure shows difference-in-difference plots for blood culture contamination (BCC) (A), length of stay (LOS) (B), days of therapy (DOT) (C), and laboratory costs in USD (D). The green line represents the treatment group (center 1), while the red line represents the control group (centers 2 and 3). The blue dashed line represents the intervention of switching from commercial ISDT to manual ISDT.
Results
A total of 12,616 patients were included in the study (7,339 preintervention, 5,277 postintervention). Baseline demographic and clinical characteristics are provided in Supplemental Table S2. Mean age was similar across arms and periods (60–61 years), and sex distribution was comparable. The treatment arm included a higher proportion of Black patients and transplant recipients than the control arm, reflecting baseline differences in case mix across centers.
Regarding secondary outcomes, the intervention had no significant effect on log-transformed hospital length of stay (ß = 0.02, P = .534). In the count model, the incidence rate ratio (IRR) was 1.03 (P = .980), indicating no significant difference in the number of vancomycin or daptomycin days among patients who received therapy. In the zero-inflated model, the IRR was 0.98 (P = .851), likewise showing no significant difference in the likelihood of patients receiving any of these antibiotics (Table 1; Figure 1B–C).
Multiple variable regressions for study outcomes
Log, Logarithmic; DOT, Days of Therapy; OR, Odds Ratio; CI, 95% Confidence Interval; IRR, Incidence Rate Ratio; SARS-COV2, Severe Acute Respiratory Syndrome Coronavirus 2; ED, Emergency Department; ICU, Intensive Care Unit. The Treated x Time variable represents the difference-in-difference (the effect of the intervention).
In contrast, laboratory-associated costs were significantly lower in the treatment group postintervention (difference $26.58 per patient, P < .001; Table 1; Figure 1D), corresponding to $75,035.40 annualized savings during the postintervention phase.
Discussion
We found that switching from commercial to open ISDT had no significant difference in BCC rates, LOS, or DOT, but did decrease laboratory-associated costs. Our previous study demonstrated that switching from no diversion to the commercial ISDT resulted in a statistically significant reduction in BCC rates. Reference Febres-Aldana, Ashley and Amenta8 These results mirror the 12 of 13 other studies that showed a reduction in BCC rates after implementing the Steripath ISDT. Reference Al Mohajer and Lasco5 Our present study found no difference in BCC rates when switching from commercial to open ISDTs, suggesting that the open ISDT may be comparable to the commercial ISDT in reducing contamination (compared to no diversion). One confounder is that the lower rate of BCC associated with ISDTs may, in part, be due to an extra level of training provided to phlebotomists and nurses that was inherent to the implementation process.
Fewer studies have examined the associated clinical outcomes after implementing ISDTs, and especially comparing one ISDT to another. Buzard et al. found a reduction of BCC rates when using Steripath ISDT compared to no diversion, but no significant changes in hospital cost, lengths of stay, or days of vancomycin use. Reference Buzard, Evans and Schroeder9 In contrast, Nielsen et al. found a significant decrease in vancomycin use with commercial ISDTs. Reference Nielsen, Nguyen and Wahl10 Arenas et al. were the first to assess two commercial ISDTs within one study, but they were individually compared to the standard of care.6 Our study is the first to directly compare one ISDT to another and assess several clinical outcomes. The laboratory-associated differences in costs are due to the higher cost of the commercial compared with the open ISDT. The lack of a significant difference in LOS or DOT makes using commercial ISDTs less compelling. The study has several limitations. As a nonrandomized, multicenter quasi-experimental analysis, residual confounding is possible, and DID estimates rely on the parallel trends assumption; while monthly preintervention outcome trajectories appeared broadly similar on visual inspection (Figure 1), unmeasured time-varying differences between centers cannot be excluded. In addition, our pragmatic inclusion criteria (all adults with index blood cultures) may introduce clinical heterogeneity (e.g., emergent line placement, prior antibiotic exposure) that was not fully measurable or adjustable. Our antimicrobial outcome was limited to vancomycin and daptomycin DOT, which may underestimate changes in broader empiric therapy. Finally, our cost assessment captured laboratory-associated costs only and did not include downstream costs of contamination (e.g., antibiotic exposure, procedures, or incremental LOS). The postintervention period was relatively short, limiting ability to determine sustainability or seasonality. More robust randomized-controlled studies will be needed to identify the true downstream effects of commercial ISDTs and lower BCC rates.
Conclusion
Switching from commercial to open ISDT had no significant effect on BCC rates, LOS, or antibiotic DOT. However, it led to a substantial reduction in laboratory costs, highlighting operational opportunities, given the financial constraints faced by healthcare systems. Future studies should include prospective, randomized control trials to thoroughly examine the effects of various ISDT outcomes and associated costs.
Supplementary material
Supplementary material for this article can be found at https://doi.org/10.1017/ice.2026.10412.
Acknowledgments
N/A. The authors have no conflicts of interest or financial support to disclose.
Financial support
None.
Competing interests
None.
