Concept and design: M Bharmal, I Katsoulis, J Chang, A Graham, A Stavropoulou, P Jhingran, CL Pashos. Acquisition of data: I Katsoulis, A Graham, A Stavropoulou. Analysis and interpretation of data: M Bharmal, I Katsoulis, J Chang, A Graham, A Stavropoulou, P Jhingran, CL Pashos. Drafting of the manuscript: M Bharmal, I Katsoulis, J Chang, A Graham, A Stavropoulou, P Jhingran, CL Pashos. Critical revision of paper for important intellectual content: M Bharmal, I Katsoulis, J Chang, A Graham, A Stavropoulou, P Jhingran, CL Pashos. Statistical analysis: I Katsoulis, A Graham, A Stavropoulou. Provision of study materials or patients: I Katsoulis, A Graham, A Stavropoulou. Obtaining funding: M Bharmal, J Chang. Administrative, technical or logistic support: M Bharmal, I Katsoulis, A Graham, A Stavropoulou. Supervision: M Bharmal, A Graham.