OSMT (Ontario Society of Medical Technologists) Practice Exam

The proper fixative for a Papanicolaou (PAP) stain is absolute ethyl alcohol. This is primarily because absolute ethyl alcohol provides optimal fixation for cytological specimens, preserving cellular morphology and nuclear detail, which are critical for accurate evaluation in cytological testing. It has the ability to rapidly penetrate cells and dehydrate them, thus preventing the degradation of cellular structures.

Using absolute ethyl alcohol allows for a more consistent and reliable staining process, which is essential for diagnostic accuracy in Pap smears that screen for cervical cancer and other abnormalities. It maintains the integrity of the sample, ensuring that subsequent staining techniques can provide clear and distinguishable results.

While Carnoy's fluid, methanol, and 95% isopropyl alcohol are used in different contexts for fixation in cytology and histology, they do not provide the same level of preservation of nuclear detail necessary for PAP staining, making absolute ethyl alcohol the most suitable choice for this specific procedure.