DNA Extracted from Cytologic Slides Is a Valuable Source for PCR-Based Molecular Tests

Area of Science:

• Molecular Biology
• Cytopathology
• Genetics

Background:

• DNA extracted from cytologic samples is utilized for molecular testing.
• Evaluating DNA quality from various cytologic slide preparations is crucial for reliable molecular analysis.

Purpose of the Study:

• To assess the suitability of DNA extracted from differently prepared cytologic slides for PCR-based molecular tests.
• To compare DNA quality and mutation detection success rates across various cytologic slide fixation and staining methods.

Main Methods:

• Collected 23 cases of papillary thyroid carcinoma or colorectal adenocarcinoma tissues.
• Prepared six touch-imprinted cytological slides per case (air-dried, fixed, stained) and FFPE tissue blocks.
• Evaluated DNA concentration, 260/280 ratio, DNA Integrity Number (DIN), and gene mutation (BRAF/KRAS) from each preparation group.

Main Results:

• DNA concentration was highest in air-dried slides and lowest in CytoRich Red Preservative-fixed slides.
• Highest DNA Integrity Number (DIN) was observed in ethanol-fixed slides; lowest in CytoRich Red Preservative-fixed slides.
• Mutation detection in BRAF/KRAS genes was successful in air-dried, ethanol-fixed, and stained slides, but largely failed in CytoRich Red Preservative-fixed slides.

Conclusions:

• Stained and unstained cytologic slides are suitable for PCR-based molecular tests.
• Ethanol fixation or short-term air-drying are recommended preparation methods for cytologic slides used in molecular testing.
• CytoRich Red Preservative solution is not recommended for preparing cytologic slides intended for mutation analysis.