Rapid Laboratory Diagnosis of Bloodstream Infections: Conventional Culture versus Molecular Methods

Abstract

Bloodstream infections (BSIs) were time-critical conditions in which diagnostic delays could prolong inappropriate antimicrobial therapy and worsen clinical outcomes. Conventional blood culture remained the reference method for pathogen recovery and phenotypic antimicrobial susceptibility testing, although its effectiveness was limited by blood volume, prior antimicrobial exposure, contamination, and prolonged incubation time. Molecular methods, including multiplex PCR, direct-from-blood assays, targeted sequencing, and metagenomic next-generation sequencing, provided faster pathogen detection and enabled the identification of selected resistance determinants. This paper used a qualitative systematic/narrative literature-review approach to compare conventional and molecular diagnostic methods based on analytical performance, turnaround time, antimicrobial susceptibility testing, contamination, clinical outcomes, cost, implementation, and equity. The reviewed evidence indicated that molecular assays provided substantially faster results but generally lacked sufficient sensitivity to replace blood culture. An integrated diagnostic approach was therefore proposed, in which high-quality blood-culture collection remained fundamental, while rapid molecular testing was used according to clinical urgency and assay coverage. The study also highlighted challenges in Pakistan and other developing economies, including limited infrastructure, financing, reagent availability, laboratory capacity, and trained workforce. Overall, the findings suggested that rapid BSI diagnosis was a socio-technical intervention that required quality specimen collection, validated interpretation, timely communication, antimicrobial stewardship, and equitable implementation.