Epidemiological, public health, and ethical considerations in the evolution of India’s COVID-19 testing strategies.
India is highly susceptible to the COVID19 pandemic due to the limited health infrastructure, dense population, significant proportion of people living in poverty, and a large elderly population in absolute terms with high prevalence of comorbidities like diabetes, obesity and undernourishment that significantly accentuate the risk of mortality . As of 28 March 2020, India has reported 987 COVID-19 cases and 19 deaths, after conducting approximately 35,000 tests .
The World Health Organization has recommended testing every suspected case for coronavirus infection, isolate the positive cases, trace all contacts, and test those who are symptomatic, to prevent the spread of the disease . However, extensive testing requires adequate availability of testing kits and skilled human and material resources for sample collection and designated laboratories that have appropriate safeguards for infection control and safety.
India adopted a graded, testing strategy for COVID-19, that initially restricted testing to only symptomatic patients who had recent international travel history, and all the symptomatic contacts of laboratory-confirmed cases. Subsequently, the testing strategy has been expanded in the 3rd week of March. The current guidelines now recommend additionally, the testing of all symptomatic healthcare workers, all hospitalized patients with Severe Acute Respiratory Illness (SARI), i.e., fever AND cough and/or shortness of breath, and asymptomatic direct and high-risk contacts of a confirmed case . Testing is available free of cost in designated government facilities, but only when meeting the testing criteria. However, it involves a significant out of pocket expense in undertaking testing in a few private labs that have been approved for the purpose.
The number of people tested for COVID-19 per million population in India is among the lowest in the world. Some experts have considered this as being inadequate in identifying the magnitude of the actual burden of COVID-19 due to the likelihood of missing a significant proportion of positive cases . Moreover, the unidentified cases can further spread the infection to their contacts and increase the risk of community transmission with an exponential increase in cases.
Nevertheless, inferences drawn from the available testing data, suggest that the testing strategy was appropriate for the following reasons.
(1). The proportion of patients testing positive for the coronavirus infection is currently < 2.6% in India, despite the expansion in the testing strategy. This persistently low rate of infectivity despite the restrictive testing criteria is also indicative of the lack of community transmission. Further testing individuals at lower risk of coronavirus infection (not having travel or COVID-19 patient contact history) will cause this proportion to reduce further. It is true that states like Kerala and Maharashtra that tested more patients also found more cases , but the larger denominator was due to a larger diaspora population mainly from the Middle East that traveled back to India belonging to these states, that obviously met the eligibility criteria for testing.
(2). Symptomatic patients with mild symptoms (notably, without shortness of breath) that don’t meet criteria for COVID-19 testing criteria were recommended self-isolation in homes and avoiding contact with other family members, and following hygiene measures. This is because even in the less likely scenario of a mildly symptomatic patient with COVID-19 being missed due to lack of testing, patient beneficence would be limited due to high chances of recovery in the absence of preexisting comorbidities and the absence of curative treatment. Consequently, an infected undetected patient with mild symptoms practicing self-isolation in household settings is unlikely to be negatively impacted due to the lack of confirmation of his/her COVID-19 status.
(3). Mass testing in Indian health settings is challenging due to a large population, limited testing capacity, and lack of effective airborne infection control measures. Infected patients in waiting queues and the queuing area of the health facilities, and during travel if using public transport, or when not using a mask could also increase the risk of infection transmission to the non-infected patients. However, the original testing strategy restricted access to COVID-19 testing. The expanded testing strategy additionally allows any individual to test for COVID-19 in select private labs, based on his/her capacity to pay, which raises concerns over equity.
(4). Several reports of home quarantine violations by Indian residents having international travel history were reported in the media, including cases of suppression of fever symptoms by use of antipyretic agents, and some of these cases were later diagnosed having COVID-19 . A more comprehensive testing strategy that tested all asymptomatic patients with travel history would have provided a higher yield of COVID19. However, the question arises as to the extent of behavior modification for self-isolation, which could be reasonably expected among the mild symptomatic, non-comorbid patients originally exhibiting social deliquescence in the counterfactual event of them having been tested and diagnosed earlier.
(5). The initial restricted testing strategy could hypothetically have missed out on COVID-19 infected SARI cases that were recommended testing by the treating physician but were not tested by the government lab if they did not meet the travel or contact history criterion. The current testing strategy has rectified this significant omission since all hospitalized patients having SARI are now required to be tested, private labs are open for testing, and testing can be conducted based on the physician’s recommendation .
Based on the available data and trends of the COVID-19 epidemic in India, the restricted testing strategy has evolved to become robust, ethical, and adequate. India is currently observing a three-week lockdown to interrupt the chain of transmission and flatten the curve. Post lockdown antibody testing in random cluster and community samples could provide valuable evidence as to the extent of spread, development of herd immunity, and infection prevalence in the community. This would ultimately determine the validity of India’s testing strategy in the management of the COVID-19 epidemic.
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Competing interests: No competing interests