The role of urine test in determining the risk of COVID-19

Considering the complexity of COVID-19, it is important for clinicians to identify at an early stage, those who are at a greater risk. It has now been established that certain routine parameters aid in recognizing the future need for admissions to ICUs. 

A simple and inexpensive urine test can provide novel insights into the pathophysiology of COVID-19 and biomarkers of disease severity. Several studies* have revealed that urinalysis of admitted patients showed a wide range of abnormalities; such as proteinuria, hematuria, and leucocytes; days before the rapid worsening of COVID-19 infection.  

Kidneys: among the first organs to be infected
SARS-CoV-2 affects not only the lungs but also the kidneys, and that too at an early stage of infection. This is because podocytes (cells found in the kidneys) express the ACE 2 receptor, making them susceptible to SARS-CoV-2 infection. 

Though the respiratory tract is the gateway for SARS-CoV-2, COVID-19-associated nephritis, which can be easily screened for, with a urine sample analysis, may be a significant predictor of unfavorable disease progression. 

Urinalysis: A simple test
It has now been established that urine tests can be used to identify high-risk patients. Various studies have proved that routine parameters have shown relevance in clinical diagnostic settings:

Proteinuria
It is a condition that indicates an increased level of protein in the urine. Proteins are usually found in the blood and normally do not pass into the urine. However, if the glomeruli or tubules in the kidneys are damaged, if there is a problem with the re-absorption of proteins, or if there is an excessive protein load, the proteins will flow into the urine.

Hematuria
Hematuria is the presence of blood in urine and is an indication of infection in the bladder, kidney, or prostate.

Urinalysis abnormalities were studied by Bonetti et al, in 226 COVID-19 Italian patients admitted to the Emergency Department. Kidney injury appeared to be a frequent finding, with a wide range of manifestations, from mild proteinuria and hematuria to severe renal failure. The analysis of the urine sediment also revealed the presence of erythrocytes and casts in nearly half of all patients.

The study highlighted another interesting aspect. Granular cylinders and tubular cells were present in frequent numbers in patients who died due to COVID-19 compared to the patients who were discharged.

In another study, conducted by the University Medical Centre, Germany, urinalysis showed that significant abnormalities were already observed days before a rapid worsening of COVID-19 infection. The urine tests of these patients revealed severe hypalbuminemia and positive results for blood, albumin, and leukocytes in urine. This further led to the conclusion that COVID-19-associated nephritis, which can be easily screened for, with a simple and inexpensive urine sample analysis, might help predict complications.

Leucocyte esterase
A specific leucocyte (white blood cell) protein, leucocyte esterase is a quick measure of the number of leucocytes in the urine. This can indicate a urinary tract infection and probable kidney damage, on further investigations.

In summary, though the respiratory tract is the gateway for SARS-CoV-2 infection, renal involvement may be a significant predictor of unfavorable disease progression.

A simple and inexpensive urine test can provide novel insights into the pathophysiology of COVID-19 and biomarkers of disease severity.

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