Using a simple lab kit, some LED lights, a hot plate, and a smartphone, a team of engineers and molecular biologists have a developed a point-of-care diagnostic test that can rapidly detect microbial pathogens in urine. New research on the device indicates it has the potential to provide quick, low-cost diagnoses of urinary tract infections (UTIs) in low-resource settings.
In a pilot study published in the journal EBioMedicine, the device, developed by researchers at the University of California, Santa Barbara and Stanford University, was compared with more costly rapid diagnostic technology and standard hospital diagnostic tests for analysis of urinary pathogens in a small group of patients with sepsis. The results of the head-to-head comparison showed that the smartphone-based real-time loop-mediated isothermal amplification (smaRT-LAMP) system matched the hospital diagnostics in detecting pathogens, but at a fraction of cost and the time.
Researchers say they believe the smaRT-LAMP system could have significant clinical potential, especially in healthcare clinics that lack sophisticated diagnostic technology.
"Although rapid diagnosis by smaRT-LAMP has utility in standard clinical diagnostics, we anticipate its immediate use in local clinics that cannot afford the tests required to ID a pathogen, which is important for prescription of the correct antibiotic," lead study author Michael Mahan, PhD, a professor at UC Santa Barbara, told CIDRAP News.
Low-cost, low-tech device
While it isn't the first attempt to harness smartphone technology for diagnostic use, Mahan and his colleagues believe the low-cost, low-tech smaRT-LAMP system may be the first smartphone-based diagnostic tool with real clinical utility in low-resource settings.
To use smaRT-LAMP, samples of urine are placed in an aluminum sample block on top of a hot plate. The samples are then mixed with chemicals that amplify bacterial DNA. The smartphone camera captures the fluorescent signal (illuminated by the LED lights) from the chemical reaction, and a custom-built app analyzes the images to measure the concentration of bacterial DNA in the samples.
The researchers estimate the cost of the materials, minus the smartphone, is around $86. By comparison, a quantitative polymerase chain reaction (qPCR) machine, which also uses DNA amplification to quickly detect bacteria or viruses, costs around $36,000.
In proof-of-concept testing conducted on mouse urine, blood, and feces samples spiked with a variety of bacterial pathogens, smaRT-LAMP showed that it could identify pathogens just as well as a qPCR device and is compatible with a diverse array of pathogens and biological specimens. But Mahan said that using the device to test urine offered the quickest path to identification of possible infection since infected urine is associated with a much higher bacterial load than blood.
"Proof of concept was much simpler for UTIs, as the clinical threshold to define a UTI is 100,000 bugs per milliliter of urine versus only one per milliliter of blood," he said.
Moreover, urine can be obtained without invasive procedures, and UTIs are among the most common types of bacterial infection.
Based on its performance with the spiked mouse urine samples, Mahan and his colleagues decided to assess whether smaRT-LAMP could have immediate clinical utility for point-of-care urine analysis in human patients. Working with physicians at a local hospital, they identified 10 patients who met the clinical criteria for sepsis and were suspected of having a urinary source of infection. Some of the patients had severe sepsis and were showing signs of septic shock.
Once again, smaRT-LAMP was able to identify to detect the bacterial pathogens in the urine—Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa—as quickly and accurately as the qPCR device, achieving diagnosis in under an hour. Standard urine cultures performed by the hospital microbiology laboratory, meanwhile, took 18-28 hours to identify the pathogens. This is important, Mahan and his colleagues note, because time to treatment is significantly associated with positive patient outcomes in emergency care for sepsis.
In addition, among the patients whose infections had spread into their bloodstream, the pathogen identified in the urine matched that of the blood.
"This concordance demonstrates the applicability of smaRT-LAMP to even the most severe cases of sepsis, with the advantage of accurate and rapid diagnosis at the POC [point-of-care] in these cases, and the potential to greatly accelerate directed therapy for urinary tract infections," the authors wrote in the paper.
The device could also be used to for rapid detection of UTIs in pregnant women, which can cause kidney infections and increase the risk for miscarriage if they go untreated.
Mahan said the next step is to see whether smaRT-LAMP works in low-resource clinics, and to continue tailoring the system to quickly detected pathogenic bacteria in human blood and feces.
Sep 20 EBioMedicine study