It is all in the bag: collodion bag versus HistoGel cell block method.

INTRODUCTION: We performed a comparison of cell blocks prepared with the collodion bag and HistoGel to evaluate the ease of embedding and cutting, performance with low cellularity specimens, time and cost per specimen, and value to support immunohistochemistry and molecular diagnostics.
MATERIALS AND METHODS: We processed 11 fresh, unfixed effusions using both the collodion bag and the HistoGel cell block preparation methods. Six immunohistochemistry stains were tested on 2 of the body fluids. DNA was extracted and quantified, and polymerase chain reaction cycle thresholds were evaluated from cell blocks prepared from 5 of the body fluids. The comparison parameters included embedding difficulty, cutting resistance, adequacy, cell yield, cell preservation, immunohistochemistry stain quality, DNA quantity, integrity, and purity. The time and cost to prepare each specimen was compared using normalized values for preparation of specimen, cost per year, and cost per specimen.
RESULTS: Each parameter was assessed for both cell block preparation methods. All 3 of the samples with moderate or poor cell yield were low-volume (5-mL) samples prepared with the HistoGel method. In contrast, the collodion bag method produced a good yield with all three 5-mL samples. DNA recovery was greater in the collodion bag method. Similar crossing threshold values in purity reactions indicated equally high-quality matrix properties for the collodion bag and HistoGel preparations. Preparation of the specimen was 10 minutes faster with the collodion bag method, and the cost for the collodion bag method was $0.24 more expensive per cell block than using the HistoGel.
CONCLUSIONS: The collodion bag method produced superior cell blocks for both morphologic and molecular studies more consistently, with lower volume specimens and with less time per specimen.