Simple Urine Test Can Diagnose Allergic Reaction in Kidneys

Acute tubulointerstitial nephritis (AIN) is a medical condition that causes inflammation of the kidneys and can result in acute kidney injury (AKI) — a rapid deterioration of kidney function. Medications used for treating gastroesophageal reflux disease, bacterial infections, and cancer are believed to trigger AIN in approximately 70% of patients. Diagnosis of AIN is typically challenging due to the absence of disease-specific signs or symptoms, often necessitating a kidney biopsy. To evade the risks associated with kidney biopsies, clinicians may assume the presence of AIN and attempt to halt the progression toward AKI by discontinuing potential offending drugs and administering corticosteroids. However, such a strategy could lead to excessive treatment if the AIN diagnosis is not accurate. Discontinued medications could encompass crucial therapies like antibiotics and anti-cancer drugs, and corticosteroid treatment presents risks such as high blood sugar, bone loss, gastrointestinal bleeding, and infections.

Now, in a study led by Johns Hopkins Medicine (Baltimore, MD, USA), researchers have identified a biomarker detectable via a simple urine test that can aid in diagnosing AIN. The study evaluated over 180 potential immune system biomarkers and determined that testing for a protein named CXCL-9 in a person's urine could provide a noninvasive method to diagnose AIN, eliminating the need for a kidney biopsy. To identify this top AIN-associated protein, the researchers tested the urine of more than 200 hospital patients with AKI for 180 potential biomarkers. They discovered that patients with AIN had significantly elevated levels of this protein in their urine compared to those without AIN, a finding which was corroborated by examination of kidney tissue samples.

The research team suggests that the urine biomarker CXCL-9 could substantially enhance clinical care by helping to confirm or exclude AIN in a large subset of patients, thereby reducing the need for kidney biopsies to cases where biomarker values are indeterminate. The team hopes that the insights from this study will also assist in the development of more effective treatments for AIN as a precursor to AKI, and for AKI itself, potentially by targeting inflammatory chemicals in the early stages.

“AIN is an allergic reaction caused by some common medications that are used routinely in a small group of patients,” said Chirag Parikh, M.B.B.S., Ph.D., director of the Division of Nephrology at Johns Hopkins Medicine. With the common assumption of a patient having AIN instead of AKI, finding a new biomarker can help eliminate the potential of a misdiagnosis. “Having a method for early diagnosis can help preserve kidney function and long-term chronic kidney disease,” added Parikh.

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