Negative predictive value of pleural fluid cytology in patients with a background of cancer by Anon, OC, Mercer, R, Asciak, R, Mccracken, D, Bedawi, E, Hassan, M, Dudina, A, Lu, Q, Tsikrika, M, Varatharajah, R, Shepherd, G, Thayanandan, A, Hallifax, RJ, Wrightson, J, Rahman, NM