Illustration of an antigen test diagnosis .. -

G. Durand / 20 Minutes

The health authorities in Charente suspect anomalies in the methods of storing antigenic tests since a screening campaign in a high school, ended with "atypical" results with many "false positives". learned Saturday by the ARS.

In December, the group of medical analysis laboratories Biogroup questioned the reliability of antigenic tests, deemed to be less sensitive than RT-PCR tests, stressing that their results included not only “false negatives” but also “false negatives”. positive ”.

The high school which had to close for fear of a source of contamination will be able to reopen its doors on Monday.

A particularly high rate of "false positives"

The questions arose after a screening operation with these rapid tests at the high school of the Oisellerie de La Couronne, near Angoulême, which ended with an "atypical result" raising fears of a massive epidemic, the prefecture explained on Friday. de Charente in a press release.

Of the 250 volunteers tested on March 9, 119 were found to be positive, an abnormally high rate, which, after verification, does not allow "to exclude the use of a defective test stock due to inadequate storage methods. », According to the prefecture.

The students and teachers presumed positive were then led to carry out the reference nasopharyngeal test, by the RT-PCR method, and the first results confirm the “atypical nature” of the first session: out of the 73 tests already analyzed, 100 % are negative.

An expertise was entrusted to the pharmacists of the Regional Health Agency (ARS) Nouvelle-Aquitaine to try to explain this high rate of "false positives".

While awaiting “conclusions”, the ARS “hypothesizes” that the storage conditions required by the manufacturer to keep the tests (“between 2 and 30 ° C”) are unsuitable.

“The storage temperatures in the high school gymnasium never dropped below 10 ° C and were therefore in line with what was requested.

It remains to be seen whether the recommended temperatures are the right ones, ”underlined Martine Liège, deputy director of ARS in Charente.

By way of comparison, she adds that "the same batch of tests was administered in another high school", this time without giving rise to abnormal results.

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