Development and Evaluation of a Rapid Diagnostic Test for Bloodstream Infections

Thesis Abstract

Bloodstream infections (BSIs) constitute a critical global health challenge due to their high morbidity and mortality rates, particularly in resource-limited settings where rapid diagnosis and timely treatment are often hindered by inadequate laboratory infrastructure. Conventional blood culture methods, although considered the gold standard, are time-consuming, often requiring 48-72 hours to yield results, which delays appropriate antimicrobial therapy and contributes to increased patient mortality and the emergence of antimicrobial resistance. This study aims to develop and rigorously evaluate a novel rapid diagnostic test (RDT) designed for the prompt detection of common bacterial and fungal pathogens responsible for BSIs, thus facilitating early intervention and improved clinical outcomes. The primary objectives are to (1) design a lateral flow immunoassay-based RDT capable of detecting key pathogens such as Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Candida albicans in blood samples, (2) optimize the assay conditions for sensitivity, specificity, and reproducibility, and (3) evaluate the diagnostic performance of the developed RDT against the standard blood culture method in clinical settings. The study adopts a cross-sectional analytical design, encompassing a two-phase approach initial laboratory development and optimization, followed by clinical validation. The population comprises 500 patients presenting with symptoms suggestive of BSIs at tertiary healthcare facilities over a 12-month period. A stratified random sampling technique is employed to select participants, ensuring representation across age, gender, and clinical severity profiles. Blood samples are collected aseptically and divided into aliquots for testing with the newly developed RDT and conventional blood culture. Data acquisition employs structured data collection forms, microbiological identification through standard biochemical tests and MALDI-TOF mass spectrometry, and RDT reading via visual interpretation complemented by portable reader devices to quantify test lines. Analytical techniques include descriptive statistics for demographic data, sensitivity, specificity, positive and negative predictive values calculated through 2x2 contingency tables, and receiver operating characteristic (ROC) curve analysis to determine diagnostic accuracy. Logistic regression models are utilized to identify factors associated with test performance, and Bland-Altman plots assess agreement between the RDT and blood culture results. Expected findings anticipate that the RDT will demonstrate sensitivity and specificity exceeding 85% for the targeted pathogens, significantly reducing turnaround time to under 30 minutes. It is hypothesized that the test will outperform traditional microscopy in terms of accuracy and ease of use, offering a viable point-of-care alternative suitable for resource-constrained environments. Additionally, receiver operating characteristic analysis is expected to reveal optimal cut-off points for pathogen detection, while agreement analysis will ascertain the consistency of the RDT with standard microbiological techniques. This research contributes novel evidence towards the development of rapid, affordable, and reliable diagnostic tools for BSIs, extending the theoretical framework of diagnostic innovation grounded in the Health Belief Model and Technology Acceptance Model, which postulate user adoption based on perceived ease of use and perceived usefulness. Practically, the study provides a validated prototype of an RDT that can be integrated into existing diagnostic workflows, thereby shortening diagnosis times and informing antimicrobial stewardship policies. In conclusion, the study underscores the importance of innovative diagnostic technologies in combating bloodstream infections and calls for their broader implementation in clinical settings. Recommendations include scaling of the RDT for diverse healthcare environments, ongoing refinement based on field data, and further research into multiplexed assays capable of detecting a broader range of pathogens. Ultimately, this work aims to impact clinical management protocols positively, reduce mortality associated with BSIs, and contribute to global efforts in antimicrobial resistance containment.