1.How is a COVID-19 test different from other tests?
Many infectious disease tests, particularly in Ghana, use rapid diagnostic test (RDT) kits. These tests use similar chromatography/affinity principles as a self-administered pregnancy test; there is an immobilised bait protein/compound which will interact with another protein/compound in the mobile phase. Once an interaction takes place, a coloured band is produced. These tests typically give yes or no answers and are not quantifiable. There are two main types of RDT tests; antigen detection, and antibody detection tests. A commonly used RDT detects malarial parasite proteins in it; a band means you have malaria. Currently 75% of malarial tests in Africa are by RDT’s (https://www.who.int/malaria/areas/diagnosis/rapid_diagnostic_tests/en/). Significant amount of HIV testing in Africa also uses RDTs.
The COVID-19 test is a quantitative reverse-transcriptase-polymerase chain reaction (Q-RT-PCR). What this molecular test detects is a part of the viral genome. It has many advantages over RDT’s:
- It is highly specific and can detect even very small amounts of virus
- It can be quantified to tell you how much virus you have in your sample
- A positive test usually means the virus is still present in the tissues
Using RDT for COVID-19 is problematic for a number of reasons
- If the testing medium is blood, very little antigen can be detected so antigen detection kits can be problematic
- Antibodies take a few days to develop. If a test is taken before antibody development, it would result in a false negative result.
- If the antibodies are IgG, there may be significant cross-reactivity with other human corona viruses to which most West Africans have been exposed to. Cross-reactivity would lead to many false positives.
- A positive test, even if specific for COVID-19 can only tell of exposure, it is difficult to know if the individual is still infected. The only way to differentiate current from past infection would be to test for levels of immunoglobulin M (IgM) versus immunoglobulin G (IgG). IgM is the first antibody made to fight an infection; IgG is made later and persists long after the infection is cleared.
2.Is Ghana’s test different from other countries?
The gold standard test for COVID-19 is Q-RT-PCR; that is what Ghana and most advanced countries use. The differences between testing for different countries mainly depends on which Q-RT-PCR assay they use and the sensitivity. Different kits amplify different parts of the virus sequence. The initial kits used at the Noguchi Memorial Institute for Medical Research (NMIMR) amplified the E (envelope) gene as well as the RdRp (RNA dependent RNA polymerase) (https://www.cdc.gov/coronavirus/2019-ncov/lab/tool-virus-requests.html) https://www.cdc.gov/coronavirus/2019-ncov/lab/tool-virus-requests.html. In the early days of the outbreak, negative results were also interrogated for other suspects such as influenzae and human corona viruses. Current tests amplify the open reading frame 1ab (ORF1a/b) and N (nucleocapsid) genes simultaneously in a single reaction. ORF1a/b and N sequences are on opposing ends of the genome so you have a better chance of getting a positive result even if the virus material is not properly extracted. There are also in-built negative controls and positive controls.
3.What is Ghana’s current testing capacity for COVID-19?
Ghana currently has enough testing kits to test almost 30000 people, with more being procured. Currently the Institute with the most capacity for testing is the NMIMR at the University of Ghana. The Kumasi Centre for Collaborative Research (KCCR) has been testing most cases from the Ashanti region. These two centres can perform slightly more than 1000 tests a day. Additional centres such as the Veterinary Services Directorate (VSD), National Public Health and Reference Laboratory (NHPHL) and the West African Centre for Cell Biology of Infectious Pathogens (WACCBIP) also have additional capacity that can increase the testing capacity to ~2000-3000 tests per day. Some of these centres are now on standby to perform tests if and when the samples exceed the ability of the two main testing centres. The main bottle necks remain the rate of sampling and the availability of virus extraction kits, which are in short supply world-wide. This together with the time that the gold standard test takes (2-6hs from sample extraction to result) means that any future mass testing would probably have to consider in-country validated rapid diagnostic kits, which would be cheaper and can be widely disseminated.
4.What lessons can other African countries learn from Ghana?
- Start early. The virology department of NMIMR obtained resources to detect the virus very early in the game. Tests for travellers with fevers as well as hospital patients with COVID-19 like symptoms started being run in February. It was also proposed to include COVID-19 testing the routine influenzae surveillance plan. The first COVID-19 positive test in Ghana was reported on 12 March, 2020.
- Ghana’s ability to detect the virus was aided by the existence of established research centres like NMIMR, which currently has WHO accredited surveillance activities for many viral diseases such as Polio and Influenzae.
- Importantly, as a research institute and not as a government laboratory, testing was devolved from the bureaucratic and political hurdles that may impact testing by government centres.
- The government of Ghana acknowledged and took advantage of the research expertise of both NMIMR and KCCR, rather than prioritizing government run labs, which might have taken longer to get up to speed. African governments should encourage and support research institutes in their borders, because academic institutions have a need to maintain scientific credibility and excellence. This is evident in the African countries who have been able to detect the virus in a timely manner. Research institutes by their nature, are more likely to have functioning equipment that can be easily co-opted for such public service unlike government labs. That kind of reputation also allows these institutions to also receive funding to aid them directly in such situations.
- Importantly, because of the richness and diversity of skills within Ghana’s scientific workforce, work being done at NMIMR and KCCR involves collaboration and personnel from other centres such as WACCBIP, VSD and PHL.
- Be transparent. Situations like this are difficult for any government. Ghana has a site that is updated daily (https://ghanahealthservice.org/covid1). Additionally, the President gives periodic updates with clarifications given by the Minister of Information. Key members of the COVID-19 response team have also had an opportunity to provide the public with information on testing.
- Ghana has also tried to allow scientists and the medical community to influence its response to the pandemic. In times like these politics has to take a backseat, Ghana’s government seems to understand this.