Nasopharyngeal (NP) vs oropharyngeal (OP) collections
There is a severe swab shortage. When an NP swab isn’t available, an OP or anterior nares swab is acceptable. The OP swabs can also be used for anterior nares but not for NP (there is no support for using an OP swab as an NP swab).There are some short swabs that can also be used for nares but are too short for OP.
For consistency’s sake and per Mayo’s recommendation for OP as the next step, Allina Health is using OP when NP isn’t available.
We don’t have a clear answer on sensitivity as there are too many confounding factors. Swabs aren’t the only factor – the viral load is highest for the first few days after symptom onset – swabs collected too early or later in the disease course will have lower sensitivity. This is a confounding factor for published studies that don’t take into account the point in the disease course when the swab was taken.
The most important factor in sampling is to get adequate upper respiratory epithelial cells (where the virus proliferates), and not just secretions.