October 24, 2020

Doctors see symptomatic rapid tests as good but not for screening


Doctors see symptomatic rapid tests as good but not for screening

Doctors see symptomatic rapid tests as good but not for screening
The province

Reducing the number of CRP that are made in Madrid and their gradual replacement by antigen test in Primary Care It has advantages such as obtaining the result in 15 minutes, although its efficacy has not been validated for asymptomatic people, nor is its use in screening the general population. The commitment of the Community of Madrid to these tests is already reflected in the statistics of covid cases of the Ministry of Health, which collects data from the cases diagnosed through antigenic tests in Madrid, Murcia and Castilla y León since Thursday.

Between September 20 and October 11, the number of PCRs performed in Madrid fell from 172,842 to 79,697, and although rapid tests were multiplied by ten, from 5,800 to 58,697, a total of 40,248 fewer tests were performed during these three weeks. This has coincided with the change of protocol on September 28 in Madrid, which no longer tests close contacts unless they are cohabitants, vulnerable people or have symptoms. The antigenic screening of the population of basic health areas (ZBS) most affected by covid began on September 29 in Puente de Vallecas and has continued in districts such as Villaverde, Usera or Ciudad Lineal, but with less public influx than expected.

Each test costs 4.5 euros while the PCR about ten times more, and the result takes 15 minutes compared to 48 hours for PCR, which “greatly facilitates the diagnosis: in the same consultation, home isolation and sick leave is determined. It is more fluid and faster”, according to Jesús Redondo , family doctor in Alcorcón. “They are very useful for diagnosing patients with symptoms for less than five days. When they have been symptomatic for more days, it is not the same as CRP. You have to carefully select which patients and when to use the test, its real effectiveness in asymptomatic patients is unknown “continues Redondo.

For this reason, the tests “are not very useful for population screening. In addition, out of a thousand people cited by SMS, 200-300 come, it cannot be said that they would work”, according to this family doctor who nevertheless considers it “a good Advance”. According to Dr. José María Molero, “the test is guided by a higher viral load; if it is not high, it is negative. The PCR can be positive with very small loads that can remain up to 20 days. infection, it is no longer contagious, “he explains.

The test if it is positive is that the person is contagious. In the case of PCR, it may be that “a third of the positives are no longer contagious, but it serves to track other people who have been infected in between by the index case, with a greater chance of finding infected who do not know it.” With the rapid test “some patients with false negatives are lost after having spent more than seven days with symptoms, it does not allow studying the contacts of the index case, but the positive is known at the moment”, he explains.

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