Collection of Nasal Secretions and Tears and Their Use in Allergology

Sveva Castelli; Stefania Arasi; Ruby Pawankar; Paolo M. Matricardi

Disclosures

Curr Opin Allergy Clin Immunol. 2018;18(1):1-9. 

In This Article

Tear Collection

Different methods and techniques allow to sample tears from the ocular surface: the microcapillary tube method[79,80] and the use of filter paper[81–83] or ophthalmic sponges[84] are the most common (Table 3). The sampling procedures are uncomplicated and do not need local anesthesia, but the recovered volumes are small or highly diluted trough tear reflex provoked by touching the conjunctiva.[85] Reflex tears and basal tears are different in composition.[86] Obtaining reproducible and unaltered samples with the minimum discomfort of the patient is thus a challenge. The ideal collection technique should be well tolerated, minimal invasive, quick, and easy to handle, and guarantee good extraction and detection of biomarkers with the current used immunological assays.

Microcapillary Tube Method

Aspiration of ocular fluid by glass capillary tubes or pipettes is performed from the external canthus of the eye (Figure 2). Widely used and validated in literature, it is considered to be the best method for avoiding reflex tearing.[3] However, handling needs experience and precision and is time-consuming.[84] Therefore, it is not always practicable in field studies or clinical routine, especially if pediatric populations are involved.[84] Furthermore, it may result an inappropriate method for anxious or uncooperative patients.[84]

Figure 2.

Sampling tear fluid with capillary tube.

Schirmer's Test Strips

Filter paper strips commonly used for the Schirmer's test in the diagnosis of dry eye are an easy and quick method for tears collection, suitable also in clinical routine. The paper strip is placed in the lower fornix of each eye and left in place until it has been wetted to the control line.[81] However, the strip may cause strong irritation and tear reflex often occurs causing unwanted dilution of analytes.[3]

Ophthalmic Sponges

Tear fluid can be alternatively collected from the external canthus of the eye by ophthalmic sponges, which seem to be well tolerated by patients.[85] Another advantage is that sponges allow standardization of the collected tear volume.[84] Sponges of different materials and various extraction buffers were combined and tested in order to optimize the tear collection method and overcome the most common limitations, making it however difficult to compare the results.[84,85,87] Another major concern is that some cytokines bind tightly to the sponges causing difficulties during the extraction procedure.[84,88] Tear reflection may occur also with this method, causing unwanted dilution.[85]

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