A simplified alternative diagnostic algorithm for SARS-CoV-2 suspected symptomatic patients and confirmed close contacts (asymptomatic): A consensus of Latin American experts

Abstract

Introduction: Latin America accounts for one-quarter of global COVID-19 cases and one-third of deaths. Inequalities in the region lead to barriers to the best use of diagnostic tests during the pandemic. There is a need for simplified guidelines that consider the region's limited health resources, international guidelines, medical literature, and local expertise.

Methods: Using a modified Delphi method, 9 experts from Latin American countries developed a simplified algorithm for COVID-19 diagnosis on the basis of their answers to 24 questions related to diagnostic settings, and discussion of the literature and their experiences.

Results: The algorithm considers 3 timeframes (≤7 days, 8-13 days, and ≥14 days) and presents diagnostic options for each. SARS-CoV-2 real- time reverse transcription-polymerase chain reaction is the test of choice from day 1 to 14 after symptom onset or close contact, although antigen testing may be used in specific circumstances, from day 5 to 7. Antibody assays may be used for confirmation, usually after day 14; however, if clinical suspicion is very high, but other tests are negative, these assays may be used as an adjunct to decision-making from day 8 to 13.

Conclusion: The proposed algorithm aims to support COVID-19 diagnosis decision-making in Latin America.

Keywords: Algorithm; COVID-19; Diagnosis; Latin America; SARS-CoV- 2.

Figure 1

A proposal for an alternative simplified diagnostic algorithm for SARS-CoV-2 suspected asymptomatic patients and close contacts (asymptomatic individuals). ^aIdeal use only in high prevalence (>5–10%) scenarios with symptomatic patients or selected settings (Emergency Rooms, elderly residences, health care personnel, surgical urgencies). The best timeframe for collection in asymptomatic individuals is 5–7 days after the close contact. Providers conducting testing on asymptomatic populations must be aware of the potential for a presumed false-positive result with an antigen test that will necessitate confirmation with a subsequent PCR test (Virginia Department of Health, 2020). ^bConsider the interpretation of the result as “Confirmed exposure to SARS-CoV-2”, and in the case of IgM positivity only, consider as a probable false positive (Kubina and Dziedzic, 2020). Repeat determination with other methods, like high-affinity antibody assays (total immunoglobulins or IgG). ^cConsider PCR pooling for population screening with low pre-test probability (<10%) to ensure assay cost-effectiveness or in negative antigen patients. If the pooling result is positive, individual rRT-PCR must be performed for each pooled sample, so the maximum number of samples to be included in a pool is 10 (CDC, 2020b). ^dConsider multiplex PCR, including influenza A/B or respiratory panel with influenza, VSR, and other viral/bacterial/fungal pathogens (Kim et al., 2020, Zhu et al., 2020). The presence of other respiratory virus does not rule out co-infection by SARS-CoV-2, therefore this possibility should not be neglected (and should be thoroughly investigated if the clinical- epidemiological context suggests it). ^eConsider antibody tests if other results are negative. ^fConsider day 14 of symptoms onset or day 21 of close contact. Ig, immunoglobulin; PCR, polymerase chain reaction; rRT-PCR, real-time reverse transcription PCR; RSV, Respiratory Syncytial Virus.

Figure 2

Estimated variation over time in diagnostic tests for detection of SARS-CoV-2 infection relative to symptom onset (modified from Sethuraman et al. (2020)). ^aDetection only occurs if patients are followed up proactively from the time of exposure. Ig, immunoglobulin; PCR, polymerase chain reaction; RT-PCR; real-time reverse transcription PCR.