Salivary tests: Their use is expanded to include large-scale screening

Nasopharyngeal RT-PCR has the best clinical performance today. However, because sampling is invasive, it is not appropriate for all situations, particularly when the test must be repeated.

Thus, in a press release dated February 11, 2021, HAS issued a favorable opinion on the support of RT-PCR tests on salivary samples in two new indications:

• second-line in contacts for whom nasopharyngeal sampling is not an option;
• first of all, in the context of large-scale targeted screening, particularly if it is repeated regularly: in schools, universities, for health care workers, EHPAD...

However, due in particular to a slightly lower sensitivity of these tests (3% to 11%) to that of RT-PCR tests on nasopharyngeal samples (nevertheless above the thresholds set), the HAS specifies in its opinion the technical conditions for carrying out these tests and the performance criteria to be met.

• Salivary sampling may be assisted or done by self-sampling at the laboratory, at home, or at a screening site. If it is difficult for the patient to spit (for example, for very young children), saliva can be collected under the tongue with a pipette.
• Sampling should be done 30 minutes after the last drink, food, cigarette (or e-cigarette), tooth brushing, or oral rinse. And the collected sample should be stored in a dry, sterile vial at room temperature.
• In the case of self-sampling, the patient must have received clear information on the conditions of its production and suitable equipment.
• The saliva sample collected must be analyzed within 24 hours.
• Because of the great heterogeneity between the kits used for the different salivary RT-PCR assays, the HAS recommends that only those which comprise at least two molecular targets and have a minimum sensitivity of 80% on the salivary sample.