US researchers have said they have developed a potential gene test for identifying acute rejection in kidney transplant patients, a finding that could eventually replace the need for biopsies.

Acute rejection after kidney transplantation occurs in about 15 percent to 20 percent of patients, even when they are treated with immunosuppressive medications, Xinhhua reported citing the researchers Tuesday.

Rejection is usually heralded by an increase in the patient's serum creatinine, a marker of kidney function, and a kidney biopsy is then performed to confirm whether rejection is taking place.

However, elevated creatinine is not sufficiently sensitive to identify all early rejection or specific enough to prevent some unnecessary kidney biopsies, so a non-invasive means of identifying acute rejection is needed, according to researchers from the University of California San Francisco.

For the new study, the researchers used an assay called quantitative polymerase chain reaction to measure the expression of 43 genes whose expression levels change during acute kidney rejection in blood samples collected from patients who had had a kidney transplant.

The researchers also found that the gene set was able to predict acute rejection up to three months before detection by biopsy, independent of age, time after transplant and sample source.

"The kSORT assay has the potential to become a simple, robust, and clinically applicable blood test," the researchers said.

The study was published in the US journal PLOS Medicine.