Efficacy and pattern of use of sputum cytology as a diagnostic test

Sputum cytology is regarded by many clinicians as a noninvasive, cheap and simple test for the diagnosis of bronchogenic carcinoma. Since the introduction of fibre-optic bronchoscopy and more easily obtained bronchial biopsies reliance on sputum cytology has diminished. However, in Edinburgh it was perceived that sputum samples were still being sent as well as, rather than instead of, bronchoscopic specimens. This retrospective study was undertaken to determine whether or not cytological examination of sputum is an efficient and sensitive test in the investigation of patients with suspected bronchogenic carcinoma. It demonstrated that the Lothian University Hospitals NHS Trust Pathology Directorate receives many sputa from departments not specializing in respiratory disease when there is no indication for the test. In addition, we have shown that the absolute sensitivity of the test is only 5% and that when there is a strong clinical suspicion of bronchogenic carcinoma the results of sputum cytology do not play a significant role in the management of the patient. We recommend that sputum cytology is restricted to those patients under the care of Respiratory Units in whom bronchoscopy is inappropriate or unsuccessful.