There are multiple definitions:

1. oropharyngeal airway(English)

   • Respiratory system, Mouth, esophagus and stomach

2. opsonophagocytic assay(English)

   • routinely used for assessing the immunogenicity of pneumococcal vaccines, with OPA data often being utilized for licensure of new vaccine formulations
   • OI, CFU, GMOI
   • Clinical chemistry, Vaccination
   • https://doi.org…28/CVI.00457-16

3. o-phthalaldehyde(English)

   • refers to a spectrophotometric assay devised to measure proteolysis
   • TNBS
   • Spectrometry
   • https://doi.org…2697(85)90549-4