Impact of a Diagnostic Stewardship Policy on Laboratory Workload, Antimicrobial Use, and Costs: Withholding Identification and Susceptibility Testing for Contaminant-Suspected Coagulase-negative Staphylococci in Blood Cultures

Abstract

Background: Blood culture contamination with coagulase-negative staphylococci (CoNS), particularly when positivity occurs in a single bottle, may lead to unnecessary organism identification and antimicrobial susceptibility testing (ID/AST), as well as inappropriate antimicrobial use. Implementing diagnostic stewardship by withholding ID/AST for suspected contaminants may reduce laboratory workload and healthcare costs.

Objectives: To compare vancomycin use and evaluate laboratory workload and cost-effectiveness before and after implementation of a policy withholding ID/AST reporting for contaminant-suspected CoNS isolates.

Methods: A retrospective descriptive study with a before-and-after comparison was conducted using data obtained from the clinical microbiology laboratory information system. Data were analyzed using descriptive statistics, the Chi-square test, and calculation of relative risk (RR) with 95% confidence intervals (95% CI).

Results: Following policy implementation, the proportion of patients receiving vancomycin for single-bottle CoNS isolates decreased significantly from 11.8% to 5.2% (X² = 9.52, p = 0.002). The likelihood of receiving vancomycin was reduced by 54% compared with the pre-implementation period (RR = 0.46; 95% CI: 0.31–0.68). Diagnostic costs associated with CoNS identification and susceptibility testing decreased by 75.1%, accompanied by a substantial reduction in laboratory workload. No requests for additional ID/AST testing were reported by treating physicians during the study period.

Conclusions: Withholding ID/AST reporting for contaminant-suspected CoNS is an effective diagnostic stewardship strategy that reduces inappropriate antimicrobial use, laboratory workload, and hospital costs.