Abstract
Purpose: :
Challenges exist in the determination of cytokines from non-stimulated, non-pooled human tears due to the limited sample volumes, low concentrations and various confounding factors. With the advance of analytical methods, it has become possible to identify specific tear components, including cytokines. The purpose of this study was to compare cytokine concentrations measured in our consecutive studies, with two different analytical methods (human, ultrasensitive, enzyme-linked immunosorbent assay (ELISA) vs. cytometric bead array technology (CBA).
Methods: :
Interleukin-6 (IL-6) and interleukin-8 (IL-8) concentrations were measured in the non-stimulated tears of patients one week after penetrating keratoplasty. IL concentrations were determined with ELISA (30 patients) or via CBA (12 patients). IL release was calculated from the concentration (pg/µl) and the volume of tears (µl) collected in 2 minutes.
Results: :
The IL-6 concentrations (mean ± SD) were 170±235 and 234±427 pg/ml (p=0.52) and the IL-8 concentrations were 220±277 and 1254±1146 pg/ml with ELISA vs. CBA (p<0.05). The tear volumes collected within 2 minutes were 58±35µl and 35±25 µl (p=0.06). The IL-6 releases were 6.6±6.7 pg and 5.5±5.4 pg (p=0.74) and the IL-8 releases were 8.6±5.4 pg and 47±71 pg (p<0.05) with ELISA vs. CBA, respectively.
Conclusions: :
Various methods used for cytokine determination and different interpretation of the data (concentration, release) might give non-comparative results. The investigator should always take into consideration the tear flow rate values. Choosing from the different methods, one should be aware of the sensitivity and of the number of cytokines to be measured.
Keywords: transplantation • cornea: basic science • cornea: tears/tear film/dry eye