Practical issues concerning tear protein assays in dry eye

Table 1 Evidence for assessing the suitability of tear proteins for clinical use

Class of tear protein	Potential clinical marker	Human tear levels show consistent dysregulation	Human tear levels linked to clinical signs/symptoms of dry eye	Change with treatment or severity of dry eye?	Biological function in dry eye pathology known?
Lacrimal protein	Lactoferrin	++++ [21]-[25]	+++ [26],[27]	+ [28]	++ [29]
Protease	MMP-9	+++ [30]-[32]	+++ [11]	+++ [33]	+++ [34]-[42]
Lacrimal protein	Lysozyme	++ [21],[43]-[45]	+ [43]	0	0
Mucins	MUC5AC	+++ [46],[47]	+ [48]	0	++ [49],[50]
Lipid binding protein	Lipocalin	++ [45],[51]	+ [52]	++ [52]	+ [53]-[55]
Interleukines	IL-6	+++ [10],[31],[56],[57]	+ [58]	++ [58]	+ [59]-[61]
Chemokine	IL-8	++ [10],[57],[62],[63]	++ [62]	0	++ [61],[64]
Keratinisation-related	S100A8/9	+++ [5],[13],[14],[65]	+++ [5],[13]	0	+ [66],[67]
Epithelial health	EGF	++ [57],[64],[68]	+ [69]	0	++ [70]
Neurotrophic health	NGF	+++ [71],[72]	++ [71],[73],[74]	++ [73],[74]	++ [75],[76]

ISSN: 2326-0254