Prospective evaluation offine needle aspiration inthe diagnosis oflung cancer

Therole offine needle aspiration biopsy hasbeenassessed prospectively inthediagnosis ofdiscrete lungshadows. Aquestionnaire wascompleted before eachof100biopsies (in97patients) todetermine theclinician's pretest diagnosis andthelikelihood ofmalignancy. Thelatter estimates were combined withthepreviously established sensitivity (71%)andspecificity (100%)ofthe procedure fordiagnosing malignancy intheunit toallow calculation ineach caseofthechange in certainty ofmalignancy asaresult oftheinvestigation. Amongthe100biopsies there were 73true positive and13truenegative results. There were no false positive results butthere were 14false negatives (cases where malignancy was later proved butwherethebiopsy didnotshowunequivocal evidence ofmalignancy). Amongthe27negative biopsy results theclinician hadestimated the likelihood ofmalignancy as80%ormore in13cases.In11 ofthese 13patients theeventual diagnosis proved tobea malignant tumour;on theother hand, sixofthe10patients given a less than50% chance ofmalignancy hadabenign outcome.A positive biopsy result was therefore quantitively of greatest value whentheprior estimate ofmalignancy was low.Inthe caseofthefalse negative results theprior probability ofmalignancy was usually sufficiently high tomerit further investigation. Itis estimated that theprocedure ledtotheavoidance ofthoracotomy inup to14of97patients.