Science
Mint Explainer: Why NIV Pune study on presence of Covid virus in stool, urine samples is important
Summary
- The study fills a gap of detection or the presence of covid-19 viral particles in urine samples that is a much easier specimen to get from patients than stools.
New Delhi: India’s top medical research body National Institute of Virology (NIV), Pune, under the aegis of Indian Council of Medical Research (ICMR), has conducted a study confirming viral load detection in stool and urine samples of covid-19 patients and transmission of the virus through faecal oral route.
Note that, since the beginning of the pandemic, Quantitative Real-time reverse transcriptase polymerase chain reaction (qRT-PCR) tests are being used all over the world to detect the virus.
In the NIV study, researchers studied the possibility of measuring covid-19 viral load using digital droplet PCR (ddPCR) directly from faecal and urine samples which is more sensitive for virus identification than RT-PCR.
Mint takes a look at the findings of the report:
What is the present status of covid-19?
It has been almost three years since the covid-19 pandemic hit, but the world still remains at risk as new strains of the SARS CoV-2 virus continue to emerge. Despite developing newer treatment and diagnostic modalities, including very effective vaccines, the disease remains one of the major challenges in countries across the world. The World Health Organization estimates that till now about 400 million people have had the infection, and 5 million have died following complications from the disease. In India, around 45 million cases have been reported with 531,918 deaths so far.
What is the present covid testing regime and its limitations?
Right now, RT-PCR detection of SARS CoV-2 through nasal and throat swabs is used to diagnose the majority of covid-19 cases and regarded as the gold standard for virus detection. However, the failure of RT-PCR in some cases in detecting the genes encoding the spike protein is a matter of concern. Also, RT-PCR is unable to quantify the viral load from borderline samples. There have been numerous testing platforms that have received FDA approval to diagnose infection. These point-of-care tests are quick, but many of them have multiple disadvantages showing low sensitivity and high false-negative rates.
What is methodology of the NIV study?
A total of 107 patients were recruited from different hospitals in Pune, between May 2020 and August 2021. RT-PCR results showed that all patients were positive for SARS CoV-2, and their faeces and urine samples collected. Around 20 samples from non-infected people were collected as a control to check the specificity of assay. According to RT-PCR results, 106 samples were positive for stool and one for urine. The ddPCR results of the 106 positive stool samples were also positive.
What did the finding suggest?
The study findings demonstrate that ddPCR performs better at detecting samples with low viral loads, like urine. On the other hand, RT-PCR was equally as accurate and reliable in the identification of viruses from stool samples. Research said that due to diarrhoea symptoms, stool is a more accurate signal of viral replication in the body along with throat and nasal swabs, and the viral load in stool samples tends to rise and then fall during the course of the illness.
While 29 urine samples out of 107 showed positive results in ddPCR, but qRT-PCR shows positive result for only two patients sample. These observations support that ddPCR is more sensitive in detecting the virus as compared to qRT-PCR.
The study fills a gap of detection or the presence of covid-19 viral particles in urine samples that is a much easier specimen to get from patients than stools.
