Vaidya, V. S. et al. A rapid urine test for early detection of kidney injury. Kidney Int. 76, 108–114 (2009).

A urine test that can rapidly detect acute kidney injury is described in a new study published in Kidney International. “The methodology is identical to the off-the-shelf pregnancy test,” says Vishal Vaidya from Harvard Medical School, Boston, MA, who describes the test as a “convenient, quick, and clear 'yes or no' diagnostic assay for kidney damage.”

Conventional tests to diagnose acute kidney injury involve the measurement of levels of serum creatinine, blood urea nitrogen, and urinary enzymes, all of which are elevated after substantial kidney function is lost. Vaidya recently reported that kidney injury molecule-1 (Kim-1) increases more than 100-fold in the kidney and urine specifically when kidney is damaged. Kim-1 (KIM-1 in humans) can serve as an early biomarker for acute kidney injury and has been shown to have a far greater sensitivity than conventional biomarkers. Currently, urinary Kim-1 measurements are analyzed using assays that require skilled workers to use large analyzers and take hours to complete. Vaidya and colleagues sought to develop an easy-to-use technology for rapid detection of Kim-1.

The team produced a lateral flow immunochromatographic assay (the RenaStick). Urine samples are placed in a well (over a nitrocellulose membrane) that contain gold nanoparticles coated with Kim-1 antibodies. “Any Kim-1 molecules in the urine attach to the antibodies and are absorbed up into the paper,” Vaidya describes. The complex travels along the membrane to a test line coated with another antibody, making a clearly visible red line. “The darker the line, the more of the Kim-1 molecules, and the worse the injury,” Vaidya adds. Results are seen within 15 minutes.

...the rapid test provides early detection of acute kidney injury...

RenaStick was evaluated in animal models of acute kidney injury and in humans. The investigators observed Kim-1 in the urine of rats with induced kidney injury and also found that KIM-1 band intensity was substantially more pronounced in humans with acute kidney injury than in healthy controls.

Vaidya describes the RenaStick as a “novel and economic tool to be able to monitor kidney damage at a very early stage,” adding, “it reduces the time and cost of detection by eliminating the dependence on large machines.” Furthermore, he says, “the FDA and its counterpart in Europe, (the European Medicines Agency) are also encouraging the use of Kim-1 detection in preclinical and clinical drug development in their Critical Path Initiative to ensure kidney safety”.

Although the test cannot measure normalized values of Kim-1, the rapid test provides early detection of acute kidney injury that could allow therapeutic intervention to prevent further kidney damage, and also “has the potential to transform safety assessment, environmental health screening and renal medicine towards effective and economic patient care,” according to Vaidya.