At-home urine test may allow for earlier lupus nephritis diagnosis
It detects ALCAM protein levels in urine, works like home pregnancy tests
A urine test that can be performed at home showed good accuracy in detecting lupus nephritis, a form of lupus marked by kidney damage, in a recent study.
This test, which works with a smartphone app, “could potentially accelerate early detection of renal involvement or disease flares in lupus patients, and hence reduce morbidity and mortality,” Richard Willson, PhD, a professor of chemical and biomolecular engineering at the University of Houston and study co-author, said in a university press release.
The study, “A novel technology for home monitoring of lupus nephritis that tracks the pathogenic urine biomarker ALCAM,” was published in the journal Frontiers in Immunology.
A lupus nephritis diagnosis currently requires a kidney biopsy
Lupus nephritis is a potentially life-threatening disease complication characterized by inflammation in the kidneys. The gold standard for diagnosing lupus nephritis is a kidney biopsy, but this is invasive and cannot be done routinely.
Recent research suggests that elevated levels of the protein ALCAM (standing for activated leukocyte cell adhesion molecule) in a patient’s urine may be a marker of lupus nephritis. Scientists led by those at the Houston school set out to create a convenient test to measure ALCAM levels in the urine.
“A large body of evidence supports the use of ALCAM as a diagnostic and disease monitoring biomarker for potential disease tracking of [lupus nephritis],” the researchers wrote.
They developed a lateral flow assay (LFA) to measure urinary ALCAM levels. LFA is the same type of technology commonly used for at-home pregnancy and COVID-19 tests; it uses immune proteins called antibodies to detect a target of interest.
The test itself is fairly straightforward to perform: a urine sample is applied and allowed to flow up a testing strip. If high ALCAM levels are detected, the testing strip changes color. Test strips are read using a smartphone.
“A point-of-care testing platform’s importance rests on its potential to empower patients to monitor their health status with convenience, thus allowing for early diagnosis and monitoring of disease progression,” said Chandra Mohan, MD, PhD, a study co-author, lupus researcher, and university professor of biomedical engineering. “The LFA represents the most widely used rapid diagnostic [point-of-care] testing platform.”
After a series of experiments to optimize the LFA and confirm this test could detect ALCAM as designed, researchers used it to assess 107 urine samples, including 30 from people with active lupus nephritis, 18 from lupus patients without active lupus nephritis, 29 from people with inactive lupus, and 30 healthy individuals as a control group.
Accuracy in distinguishing active lupus nephritis patients from controls
To assess its accuracy in detecting active lupus nephritis, researchers calculated the area under the receiver operating curve, or AUC — a statistical measure of how well a test can differentiate between two groups of people. AUC values can range from 0.5 to 1, with higher values reflecting a better ability to tell two groups apart.
The test’s AUC for detecting people with active lupus nephritis compared with healthy controls was very high at 0.93. The AUC for detecting those with active lupus nephritis compared with lupus patients without active lupus nephritis also was high at 0.86.
Additional tests where urinary ALCAM levels were normalized based on the levels of a urine protein called HVEM showed generally comparable results. While researchers stressed that further testing is needed to validate the findings, this suggests that measuring only one molecule (ALCAM) is sufficient to provide clinically useful information, which “greatly simplifies assay design and final cost to the patient.”
“The LFA tests for both non-normalized and normalized [urinary] ALCAM exhibited excellent accuracies in distinguishing active lupus nephritis from healthy controls,” Mohan said.
Scientists emphasized that this LFA test has only been used in a laboratory setting so far, and further clinical testing will be needed to see if it can truly be an effective at-home test. Still, results suggest this test could make it easier to monitor for lupus nephritis in individuals with lupus, and to track disease activity in people diagnosed with lupus nephritis.
Timely identification of lupus nephritis could allow for faster treatment initiation and, ultimately, better patient outcomes.
“This less-expensive and easily-repeatable alternative to a repeat renal [kidney] biopsy if offered as a home test, could greatly facilitate timely adjustment of immunosuppressants, without the risks of repeat renal biopsies,” the researchers wrote.
“This may allow the proactive institution of therapeutics and even preventive strategies in [lupus nephritis], while minimizing treatment-related side effects,” Mohan said.