Quantitative INTERSPECIMEN variability during biphasic pleural fluid cytological sampling in adenocarcinoma effusions

Given that cytology of adenocarcinoma-induced pleural effusions has a high diagnostic yield, we have comparatively evaluated the cytological information of smears during biphasic sampling of pleural fluid in patients with metastatic pleural adenocarcinoma from various primary sites.

We studied 25 male and 21 female patients, aged 59.4 ±17.2 years (mean ± SD) with unilateral malignant effusion of varying magnitude due to confirmed adenocarcinoma from various primary sites. At thoracocentesis we collected two 30-ml samples of pleural fluid, the first at the very beginning of fluid aspiration (S1) and the second just before termination of fluid removal (S2) and recorded the volume of fluid aspirated between the 2 samples. Cytological smears were examined under light microscopy by 3 independent cytologists after Papanicolaou stain. Quantitative assessment of cell types was averaged among 50 visual fields for each smear.

In S1 versus S2 the mean number of mesothelial cells was 7.8 ± 4.8 versus 12.1 ± 5.4 (mean ± SD), of lymphocytes 64.6 ± 12.9 versus 85.9 ± 17.4, of neutrophils 8.5 ± 4.4 versus 11.7 ± 5.2, of eosinophils 1.5 ± 0.3 versus 1.7 ± 0.8, and the number of malignant cell aggregates(NMCA) was 11.9 ±4.9 versus 20.7 ± 5.1. The differences in numbers of all cell types including NMCA were statistically significant between S1 and S2 (P < .01). A strong significant linear association between S2/S1 ratio of NMCA and the volume of fluid aspirated between samples was also found (95% confidence interval [CI], 0.209-0.236, P-value < .001).

Specimens aspirated before completion of fluid drainage are shown to contain significantly more diagnostic information than those aspirated at the beginning of fluid removal.