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Test positivity - evaluation of a new metric to assess epidemic dispersal mediated by non-symptomatic cases.


ABSTRACT: Epidemic control may be hampered when the percentage of asymptomatic cases is high. To estimate whether test positivity may assist in policy-making, it was explored in the first 60 to 90 epidemic days in six Latin American countries that reported their first COVID-19 case between February and March, 2020: Argentina, Bolivia, Chile, Cuba, Mexico, and Uruguay. Test positivity (TP) is the percentage of test-positive individuals recorded on a given day out of all individuals tested on the same day. The epidemic data of the country infected last (Uruguay) was first analyzed to evaluate TP as well as: (i) the daily ratio of secondary over primary infections (apparent reproductive ratio or ARR); (ii) tests conducted per million inhabitants (TPMI), (iii) the temporal data on the number of active cases (all test-positive cases minus deaths and recovered patients), and (iv) that of recovered patients. Later, significant patterns identified in the first step were assessed in the six countries. The Uruguayan data indicated that (i) TP was positively correlated with the ARR (r=.92, p<0.01); (ii) TP informed more than the ARR: while major data departures revealed by the ARR were also detected by TP, TP exhibited patterns not shown by ARR; and (iii) three temporal stages were observed, which differed from one another in both TP and TPMI medians (P<0.01) and, together, revealed a negative relationships between TPMI and TP. The six Latin American countries showed that TP was positively correlated with deaths/million inhabitants or DMI (r=.62, p<0.01). The temporal analysis of policies revealed four patterns: (1) low testing and high DMI, (2) high testing and low DMI; (3) an intermediate pattern, and (4) high testing and high DMI (where isolation was not pursued). Findings support the hypothesis that test positivity may inform as much as, if not more than classic metrics, such as the TPMI. If complemented with high-resolution geographical data, these indicators could inform policy-makers when and where epidemic control measures are or are not successful. .

SUBMITTER: Fasina FO 

PROVIDER: S-EPMC8144156 | biostudies-literature |

REPOSITORIES: biostudies-literature

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