Introduction An improved method for sampling nasal mucosal lining fluid (MLF), termed nasosorption, utilises a synthetic absorptive matrix (SAM) (Accuwick Ultra, Pall). Conventionally, Whatman's filter paper has been used for absorption of nasal MLF, but this natural cellulose source has the capacity to bind mediators, causing eluted fluid to have decreased and variable detectable levels of mediators. Nasal lavage has the problem of diluting MLF and this also causes detectable levels of mediators to be low. Strips of Accuwick are effective for nasosorption in adults following nasal allergen challenge and for sampling children with active rhinitis. However, Accuwick is no longer manufactured and we wished to validate an alternative SAM (Leukosorb, Pall).
Methods Sputum supernatant (40 μl) from a subject with COPD as well as a standard preparation of cytokines was spiked onto Accuwick and Leukosorb strips. Following elution by spin filter centrifugation, the MesoScale Diagnostics (MSD) multi-immunoassay platform was used to assess levels of IFN-γ, IL-10, IL-12 p70, IL-6, IL-8, and TNFα. After absorption to Accuwick and Leukosorb, elution was compared with and without buffer (PBS with BSA (1%) and Triton X (1%)), prior to immunoassay of the recovered sample.
Results Without buffer the recovery of 7 cytokines after the sputum supernatant was applied to Accuwick was a mean of 17.6% (range 1–100%), while recovery was a mean of 20.2% (range 2.9–92.5%) using Leukosorb. Addition of the buffer prior to elution of the fluid increased mean recovery to 61.8% when employing the Leukosorb system. Finally, in a direct comparison when employing Leukosorb and Accuwik for nasosorption in different nostrils after nasal allergen challenge in a single subject, Leukosorb resulted in higher detectable IL-5 levels in MLF.
Conclusion Leukosorb appears to be a superior alternative to Accuwick Ultra for nasosorption in terms of recovery of cytokines. Addition of a buffer containing detergent and protein prior to elution significantly increases recovery. SAM has the potential to be employed in the upper and lower respiratory tract to sample undiluted MLF.