IL6 and myalgic encephalomeyelitis/chronic fatigue syndrome: The levels of IL-6 in tears correlated well with OSDI score (R = 0.67, P<0.001; Fig 3E), Schirmer I test (R = -0.64, P<0.001; Fig 3F), BUT (R = -0.86, P<0.001; Fig 3G) and CFS score (R = 0.91, P<0.001; Fig 3H).