We describe the detection characteristics of a device the Resonant Coil Magnetometer (RCM) to quantify paramagnetic particles (PMPs) in immunochromatographic (lateral flow) assays. Lateral flow assays were developed using PMPs for the measurement of total prostate specific antigen (PSA) in serum samples. A detection limit of 0.8 ng/mL was achieved for total PSA using the RCM and is at clinically significant concentrations. Comparison of data obtained in a pilot study from the analysis of serum samples with commercially available immunoassays shows good agreement. The development of a quantitative magneto-immunoassay in lateral flow format for total PSA suggests the potential of the RCM to operate with many immunoassay formats. The RCM has the potential to be modified to quantify multiple analytes in this format. This research shows promise for the development of an inexpensive device capable of quantifying multiple analytes at the point-of-care using a magneto-immunoassay in lateral flow format.

Introduction: Urinary tract infection (UTI) is the most common bacterial infection independent of age. Currently, the gold standard for diagnosis of UTI is based on the presence of bacteria together with white blood cells in the urine to distinguish significant infection vs contamination. Unfortunately, white blood cell count in the urine is non-specific. An ideal biomarker should be elevated in all UTIs, irrespective of the causative organism, and remain low in the absence of infection or systemic inflammation. The purpose of this proof-of- concept study was to examine whether IL-8 could act as an efficacious biomarker for UTI infection in combination with confirmed bacterial infection. Methods: In this study, IL-8 levels were measured in anonymised urine samples sent to the pathology laboratory for microbiology testing using commercially available ELISA kits. The urine samples tested had laboratory confirmed infection with Escherichia coli, Proteus , or Klebsiella bacteria. Results: The results demonstrated that although the IL-8 levels were variable for the 3 different causative agents of UTI tested, there was a significant difference between no growth samples and combined UTI samples. Of other biomarkers tested only lactoferrin gave comparable results to IL-8. Discussion: The IL-8 data presented is consistent with other published work and suggests that testing for IL-8 with measurement of uropathogenic bacteria could be a sensitive screening test for an accurate diagnosis of active UTI infection, excluding contamination and systemic inflammation. Larger studies with integrated clinical data are necessary to explore this further.