One in 4 patients with COVID-19 display the SARS-CoV-2 spike protein in their urine along with high albuminuria, suggesting the viral infection leads to kidney abnormalities, according to findings from a recent study.
Investigators developed an antigen capture assay to detect SARS-CoV-2 spike protein in urine samples. They tested urine samples from 132 adults and children from Yale New Haven Hospital and the Children’s Hospital of Philadelphia, of whom 106 tested positive for COVID-19 according to PCR testing of nasopharyngeal swabs.
Assay results showed that 23 of 91 (25%) adults with COVID-19 had SARS-CoV-2 spike S1 protein in their urine, Choukri Ben Mamoun, PhD, a professor of medicine (infectious diseases) at Yale School of Medicine in New Haven, Connecticut, and colleagues reported in Kidney360. No child with a positive PCR test had evidence of the spike protein in urine, although 1 child with a negative PCR test did. In a sensitivity test, the assay detected no spike protein in 20 urine samples collected before the start of the pandemic.
In addition, only 1 adult with COVID-19 had detectable viral RNA in urine, suggesting that the presence of the spike protein was not due to the presence of SARS-CoV-2-infected cells in the kidney. In addition, 24% and 21% of the adults with COVID-19 displayed high levels of albumin and cystatin C in urine, respectively. Albuminuria exceeding 0.3 mg/mg of creatinine correlated with the presence of spike protein, the investigators reported. There were no correlations between the presence of SARS-CoV-2 spike protein and cystatin C, creatinine, body mass index, age, gender, or duration of hospitalization.
“Altogether, our data suggest that the presence of spike protein in urine samples of some COVID-19 patients may still be indicative of an unknown or unpredicted kidney injury, most likely spilling of spike protein from serum,” Dr Mamoun’s team stated.
Notably, other research has associated proteinuria and microscopic hematuria with severe COVID-19 disease.
“The predominant form of kidney injury in COVID-19 seems to be acute tubular injury that might be secondary to cytokine storm or shock. Direct viral infection while present, may only occur in the most severe cases as noted in autopsy studies,” the authors wrote.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
George S, Chattopadhyay Pal A, Gagnon J, et al. Evidence for SARS-CoV-2 spike protein in the urine of COVID-19 patients. Published online April 12, 2021. Kidney360. doi:10.34067/KID.0002172021