Result Turnaround Time of RT-PCR for SARS-CoV-2 is the Main Cause of COVID-19 Diagnostic Delay: A Country-Wide Observational Study of Mexico and Colombia.

Abstract

Delay in COVID-19 diagnosis due to late real-time reverse transcription-polymerase chain reaction reporting has been described to be an important cause of suboptimal COVID-19 surveillance and outbreak containment. The objective of the study was to determine the duration of diagnostic delay due to test turnaround time and its association with marginalization status. In this observational study using national open data of Mexico and Colombia, we quantified the delay in COVID-19 diagnosis that occurred in both countries. We considered two periods that contributed to the delay in diagnosis: the time from symptom onset until testing (delay-one) and test turnaround time (delay-two). Marginalization status was determined according to country-specific scores. Among 3,696,773 patients from Mexico and Colombia, delay-two was generally longer than delay-one. Median delay-one was 3 days and delay-two 7 days in Colombia, while in Mexico, they were 3 days and 4 days, respectively. In Colombia, worse marginalization status prolonged delaytwo. In Mexico, a lower number and percentage of rapid tests were performed in areas with worse marginalization. Diagnostic delay was mostly due to test turnaround time. Marginalization status was an important barrier to diagnostic test access.