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Resolving Nigeria's Covid-19 testing debacle 11 May 2020

Nobody currently understands the spread of Covid-19 in the Nigerian population. The Nigeria Centre for Disease Control (NCDC) data shows states that have more or less cases than others. Using this data of the number of cases to infer that only an insignificant number of people have been infected by the coronavirus disease in Nigeria would, however, be dangerously misleading. The current test results are lagging indicators of the spread of the disease in the country.
    
Certainly, the country is not testing enough to understand the spread of the pandemic within its borders. Ghana, a nation with less than one-sixth the population of Nigeria, has mobilised more than seven times the tests conducted by its much bigger West African neighbour. However, Nigeria's testing problems are not limited to the sorely inadequate capacity; the testing approach has a methodological pitfall, which means that even if one million people could be tested, the data would not represent what would be obtainable from the entire population of over 200 million.

The key to having close to the actual rates of infection in Nigeria is random population testing. So far, the NCDC has focused on Covid-19 diagnostic testing. This entails testing people who are currently sick, those who recently traveled to high-risk countries and the contacts of persons who have tested positive for the disease. NCDC's testing approach needs a shot in the arm with population screening for Covid-19 to give us a true picture of how many people in Nigeria are, or have been, infected with the disease.

In an op-ed published in the Conversation, a media platform for the academic and research community, Dartmouth College professors, Daniel N. Rockmore and Michael Herron, said, “Testing symptomatic patients reflects a classic error in sampling.” This is a major statistical error that is inherent in NCDC’s testing data. For one thing, the agency’s data does not provide a source of actionable information for implementing interventions aimed at protecting at-risk populations and taking the necessary precautions.

On April 27, when President Muhammadu Buhari announced a gradual easing of lockdown restrictions in Abuja, Lagos and Ogun States, the data did not show how measures to curb the spread of the virus had affected the infection rates across the populations in those places he had ordered people to stay at home for five weeks. It is the same dilemma of flying blind in the fight against Covid-19 across the other states of the federation where governors have imposed some restrictions.     

Apart from being able to assess the prevalence of Covid-19 in the Nigerian population, random testing can incorporate antibody tests to help identify individuals in the population who have previously been infected with the coronavirus and now possess antibodies that provide immunity to the virus. The benefit of incorporating antibody tests in the proposed testing methodology is that we will know what proportion of the population has developed Covid-19 immunity. According to the Johns Hopkins Bloomberg School of Public Health, when most of a population, usually 70-90 per cent, is immune to an infectious disease, they provide indirect protection – or herd immunity – to those who are not immune to the disease.

Without randomly testing the population, we cannot know the asymptomatic spread. Some studies suggest that between 25-50 per cent of people with Covid-19 don't show any symptoms. These are the silent spreaders of the disease. About half of those who tested positive in Iceland had no symptoms of the disease at the time of their tests. Early results in the Nordic island nation's random population testing showed some important discoveries, including the fact that between 0.3 per cent and 0.8 per cent of the population was infected with Covid-19.

There are still so many unknowns about Covid-19. Medical professionals are confounded by the disease. According to Clifford Marks and Trevor Pour, both physicians at Mount Sinai Hospital in New York, Covid-19 has been shown to damage multiple organ systems, including the lungs, the heart, the kidneys, and the brain. "It’s a disease of remarkable complexity, which even the most experienced doctors are struggling to understand," they wrote in an article for the New Yorker.

As much as 30 per cent of Covid-19 tests are said to produce false negatives in the United States, raising questions about the reliability of the tests. Other imponderables include the lingering symptoms some recovered patients continue to have weeks after testing negative twice.  Some patients in China, Japan and South Korea who had reportedly recovered from the disease have now tested positive again. Some countries that successfully flattened the curve began to see new spikes in case counts last month.        

Under the circumstances, we need more credible data through random population testing, which would inform the right policy responses and preventative strategies. My good friend, Shadrach Peter, a management scientist, said a multi-stage sampling procedure, a type of cluster sampling, can be used to conduct random tests on selected people across the country. This would entail selecting one state from each of the six geopolitical zones in the first stage. The next stage would involve one local government area from each of the 109 senatorial districts and randomly selecting for inclusion. Random sampling technique would also be more representative of the cross section of Nigeria.

Randomly testing a sample of about 100,000 individuals in Nigeria would give more precise understanding of the spread nationwide than supposing the NCDC were able to test, let’s say, 500,000 individuals, comprising suspected coronavirus cases and the contacts of infected persons that require diagnostic testing. While testing the people for both the virus and antibodies, the random tests would be accompanied by questionnaires to help understand the prevalence among those with symptoms and pre-existing conditions.

NCDC can address the challenge of limited resources for this task by leveraging the capacity of National Bureau of Statistics (NBS) or collaborating with statisticians across the federal universities. The refined data would include the rate of asymptomatic cases, states and regions with Covid-19 high-risk groups, people who have developed immunity, among other variables.

The current flow of official data on the pandemic can only lead to making very costly policy missteps, continuing on the trajectory of ineffective interventions and prolonging the pandemic that has already worsened the social and economic conditions in the country.