- Answer to the Letter to the Editor of Gui-Tao Li et al. concerning: %26quot;A systematic review and meta-analysis of biological treatments targeting tumour necrosis factor alpha for sciatica%26quot; by Williams NH, Lewis R, Din NU, Matar HE, Fitzsimmons D, Phillips CJ, Sutton A, Burton K, Hendry M, Nafees S, Wilkinson C (2013) Eur Spine J; 22:1921-1935