The value of multiple preparations in the diagnosis of malignant pleural effusions. A cost-benefit analysis

A cost-benefit analysis of five techniques employed in processing 108 malignant pleural effusions for cytopathologic examination was performed. Ethanol-fixed, Papanicolaou-stained smears were positive in 68% of the effusions, air-dried Diff-Quik-stained smears in 66%, Cytospins in 83%, cell blocks in 85% and Millipore filters in 85%. Examination of one air-dried smear and one ethanol-fixed smear yielded a diagnostic sensitivity of 82%. Using a combination of two smears and one of three concentrating techniques (Cytospin, cell block or Millipore filter) would have provided a diagnosis in over 90% of the effusions. The use of four or more preparations provided more sensitivity than did three preparations and decreased the likelihood that a malignant diagnosis would be based on the findings in only one preparation. The costs related to disposable materials and the College of American Pathologists (CAP) work load estimates for specimen preparation, staining and screening were compared. These data may be useful in developing optimal protocols for pleural effusion preparation in laboratories with specific work load requirements and limited resources.