Sodium Alginate and Plasma Thrombin Methods of Cell Block Preparation in Body Fluid Cytology: A Comparative Study

Cytology laboratories handle a substantial number of effusion fluid samples, and preparation of cell block with immunohistochemistry (IHC) has become an integral part. The routinely used plasma thrombin (PT) method is expensive, and a cost-effective alternative is the need of the hour. This study aimed to find the level of agreement between the sodium alginate (SA) and PT methods for cellularity, cytomorphology, and artefacts.

A total of 76 samples received in the cytology laboratory were evaluated. The cell blocks were prepared using the PT (routine) and SA methods from the cell sediment. Haematoxylin and Eosin sections from cell blocks were evaluated. Two cytopathologists scored the quality in a blind fashion by assessing cellularity, cytomorphology, and artefacts.

The study showed comparable performance between the two methods in terms of cellularity and cytomorphology. Satisfactory cellularity was observed in 93.4% of cases with PT and 96.0% with SA, while well-preserved cytomorphology was noted in 84.2% and 72.3% of cases, respectively. However, a notable difference was seen in the background of the SA cell block section in the form of a gel-like artefact. A few IHC markers were attempted only on the SA cell block, and the results were excellent.

Overall, the two techniques performed similarly. However, artefacts were present in the SA method, which did not affect the diagnosis. IHC was feasible and diagnostically interpretable on SA cell blocks. For routine cytology diagnostics, sodium alginate cell blocks can be a viable alternative to plasma thrombin cell blocks in resource-poor settings.