Penn Foster Cytology Practice Test

Fluid samples intended for smears are ideally collected in EDTA tubes, commonly referred to by their lavender tops. EDTA (ethylenediaminetetraacetic acid) acts as an anticoagulant by binding calcium, which is critical for blood clotting. This allows for the preservation of cellular morphology and viability within the sample, ensuring that the cells remain intact for accurate microscopic examination. The use of EDTA therefore facilitates a proper cytological evaluation, making it the preferred choice for fluid samples meant for smears.

In contrast, other types of tubes present different properties that are less suitable for this purpose. Sodium citrate tubes are typically used for coagulation studies, while heparin tubes can alter cell morphology and may not preserve cellular detail as effectively. Serum separator tubes, designed for collecting serum after clotting, can lead to cellular deterioration as well. Each of these alternatives has specific uses that do not align with the requirements for optimal smear preparation.