COVID-19: False Negatives / Projections for Africa / Predictive Biomarkers

By Kelly Young

Edited by André Sofair, MD, MPH, and William E. Chavey, MD, MS

Here's a quick look at some of the latest developments on novel coronavirus disease (COVID-19):

False-negative results on RT-PCR: Reverse-transcriptase polymerase chain reaction (RT-PCR) tests provide little diagnostic value immediately after SARS-CoV-2 exposure. The probability of false-negative results is 100% on the day of exposure, falling to 38% when symptoms begin roughly 4 days later and then to 20% at 3 days after symptom onset. Then it begins to increase again. In the Annals of Internal Medicine, the researchers conclude: "Care must be taken in interpreting RT-PCR tests for SARS-CoV-2 infection — particularly early in the course of infection — when using these results as a basis for removing precautions intended to prevent onward transmission. If clinical suspicion is high, infection should not be ruled out on the basis of RT-PCR alone, and the clinical and epidemiologic situation should be carefully considered."

Predicted spread in Africa: A modeling study from the World Health Organization predicts that with widespread and sustained transmission, 22% of the population of the WHO African Region, or 223 million people, will be infected with SARS-CoV-2 in the first year. An estimated 150,000 could die. The authors note that there appears to be a slower rate of infection in Africa, and death rates are lower than in other parts of the world.

Three predictive biomarkers: Using machine learning, researchers have identified three biomarkers that can predict mortality in patients with COVID-19. They used blood samples from nearly 500 COVID-19 patients in Wuhan, China. Levels of lactic dehydrogenase, lymphocytes, and high-sensitivity C-reactive protein were all associated with increased mortality risk. The findings appear in Nature Machine Intelligence.