GUWAHATI, April 22 - With many states raising doubts over the accuracy of the rapid test kits procured from China, experts in Assam too have felt the need to validate the kits before using them for detecting COVID-19 infection in the State.
The State�s health department yesterday had suspended its plan to begin rapid testing � which was scheduled to begin today � following an advisory from the Indian Council of Medical Research (ICMR) which said it needs to check the kits first.
The Central government had provided the State 9,600 kits � LIVZON IgM/ IgG diagnostic kit � procured from China. This kit was among 23 other kits manufactured by different firms found to be �satisfactory� when validated at the National Institute of Virology (NIV) in Pune.
The kit with the State government performs rapid diagnostic tests based on host antibody detection.
A senior microbiologist here told The Assam Tribune that like in any viral infections, antibodies for COVID-19 too starts appearing in the blood after about seven days of onset of infection.
�The rapid antibody test for COVID-19 detects antibody to coronavirus after about seven days of infection. So detection of antibody by rapid test can be done in those patients who have a travel history or had a contact with positive patients,� the microbiologist said.
Citing studies which suggest that patients develop antibody response only in the second week after onset of symptoms, the World Health Organization (WHO) further says that strength of antibody response depends on several factors, including age, nutritional status, severity of disease, and certain medications or infections like HIV that suppress the immune system.
�This means that a diagnosis of COVID-19 infection based on antibody response will often only be possible in the recovery phase, when many of the opportunities for clinical intervention or interruption of disease transmission have already passed. Antibody detection tests targeting COVID-19 may also cross-react with other pathogens, including other human coronaviruses and give false positive results,� a WHO advisory stated.
WHO feels that tests to detect antibody responses to COVID-19 in the population can, however, be critical to support the development of vaccines, and to add to the understanding of the extent of infection among people who are not identified through active case finding and surveillance efforts, the attack rate in the population, and the infection fatality rate. For clinical diagnosis, however, such tests have limited utility because they cannot quickly diagnose acute infection to inform actions needed to determine the course of treatment.
State health experts say though confirmatory gold standard test remains the RT-PCR yet in view of heavy sample load and requirements of biosafety for testing which is not available in all the hospital set-ups, the rapid tests, which uses only blood samples and has minimal risks to laboratory personnel performing the tests, seem like a boon.
�But there have been reports of certain rapid kits which are showing invalid results, particularly those from China. We have placed orders for rapid kits from South Korea as they seem to give better results. But from whatever sources we procure the kits it should be first validated and confirmed by testing with known positive and negative samples. Only then we can be able to use it for the patients. Also the sensitivity and specificity of the test kit should be checked prior to initiation because it may again give invalid results or false positive results too,� another microbiologist said.
