Formalin-fixed, paraffin-embedded (FFPE) tissue is a key resource in diagnostic labs. The quality of these samples directly impacts test accuracy. Selecting the right samples is critical to ensure dependable results. Let’s explore how to assess FFPE for reliability in diagnostic use.
Check Fixation Time and Method
Fixation is the first step that determines tissue preservation. If done incorrectly, it leads to a loss of key markers. The quality of FFPE sections depends heavily on proper fixation techniques. Tissues should be placed in 10% neutral-buffered formalin for optimal preservation.
Samples should remain in fixative for 6 to 48 hours. Less than six hours may cause incomplete fixation. Overexposure beyond 72 hours may damage nucleic acids and proteins. Avoid samples with inconsistent fixation history or unknown processing timelines. Always document fixation start and end times to maintain sample traceability.
Inspect Tissue Morphology and Embedding Quality
Tissue architecture must remain intact to allow accurate interpretation. Shrunken or distorted tissues signal poor processing. Look for uniformity and minimal cracks within the block. The tissue should appear well-oriented and fully embedded.
The sections must have clean, defined edges. Irregularities affect slide quality and test reproducibility. Embedding should center the sample properly without folding or tilting. Disorganized samples are less reliable for molecular testing and downstream assays.
Review Section Thickness and Consistency
Section thickness is critical for clear visualization and accurate results. Check the recommended ideal thickness as reported in research. Thicker sections reduce detail, while thinner ones may tear or fold.
To maintain consistency and reliability, keep these key points in check:
- Use a well-calibrated microtome to produce uniform sections
- Avoid sections that wrinkle or fragment during mounting
- Check for dehydration signs or poor-quality paraffin if breakage is frequent
- Ensure blades are sharp and properly aligned during each cut
Even slight differences in thickness may influence stain absorption and image clarity. These variations can impact the consistency of quantification results. Regular equipment checks and monitoring paraffin quality support more uniform slide preparation. Small adjustments contribute to improved diagnostic reliability.
Evaluate Storage Conditions and Age of Blocks
Storage plays a major role in sample stability. Humid or hot environments speed up degradation. Ideally, tissue blocks should be kept in a dry, cool place. Use sealed containers or storage drawers for long-term safety. Blocks over ten years old may lose molecular integrity. DNA and RNA quality decline with time.
Select samples stored for less than five years for optimal results. Always confirm block age and storage records before use. Also, label integrity matters. Faded or missing labels lead to confusion. Each block should have clear, legible identifiers. Maintaining proper records helps prevent misidentification and mix-ups.
Assess Staining Results and Background Clarity
Stained slides reflect overall sample quality. Weak or patchy stains may indicate processing faults. Hematoxylin and eosin (H&E) stains should reveal clear nuclei and cytoplasm. Check for contrast and even color distribution. The background should appear clean with minimal debris. Excessive staining blur may suggest paraffin contamination. Reliable slides show crisp structures and minimal noise. Clear visualization enhances test confidence and accuracy.
Use known control tissues to compare staining consistency. Variability across slides may require further investigation. Consistent coloration and structure recognition support better diagnostics. Quality stains make a strong difference in the final interpretation.
Selecting the right tissue blocks improves both histology and molecular diagnostics. Each step from fixation to staining plays a role in maintaining quality. By ensuring the integrity of FFPE sections, labs can reduce errors and deliver consistent diagnostic outcomes. Reliable testing starts with choosing the best-prepared samples. A commitment to quality at every stage ensures dependable results every time.