Histopathology

Characterising structural change at the cellular and tissue levels

In the context of Investigational New Drug (IND) applications, histopathology testing is of paramount importance for assessing the safety profile of a drug candidate. Histopathology involves the microscopic examination of tissues to identify and characterise structural changes at the cellular and tissue level. The findings from histopathology studies contribute valuable information to support regulatory submissions and play a crucial role in the overall safety assessment of the drug.

Here's why histopathology testing is important in the context of IND applications:

Identification of Organ-Specific Effects
Histopathology allows for the identification of organ-specific effects induced by the drug candidate. It helps determine if there are any structural changes, lesions, or abnormalities in organs/tissues exposed to the drug.

Assessment of Target Organ Toxicity
Histopathological examination is instrumental in assessing target organ toxicity. It helps identify whether the drug is causing adverse effects in specific organs or tissues, providing insights into potential safety concerns.

Detection of Morphological Changes
Histopathology enables the detection of morphological changes, such as cellular degeneration, necrosis, inflammation, fibrosis, and hyperplasia. These changes can indicate the impact of the drug on tissues and organs.

Characterisation of Adverse Events
Histopathological analysis assists in characterising adverse events observed in other non-clinical toxicity studies. It helps link clinical signs and symptoms to underlying structural changes, providing a comprehensive understanding of the drug's effects.

Risk Assessment and Mitigation
Histopathology findings contribute to risk assessment and mitigation strategies. Understanding the nature and severity of histopathological changes aids in determining the potential risks associated with the drug's administration.

Dose-Response Relationships
Histopathology studies, when conducted at different dose levels, contribute to establishing dose-response relationships. This information is critical for determining the threshold for adverse effects and defining a no observed adverse effect level (NOAEL).

Integration with Other Safety Studies
Histopathology data are integrated with findings from other safety studies, such as clinical pathology, toxicokinetics, and in vivo toxicology studies. This integrated approach provides a comprehensive view of the drug's safety profile.

Regulatory Compliance
Regulatory agencies, such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), require histopathology data as part of the safety assessment for IND applications. Compliance with regulatory standards is essential for obtaining approval to proceed with clinical trials.

Documentation of Findings
Histopathology reports document and communicate the detailed findings of tissue examinations. These reports are included in the IND submission and serve as a critical component of the regulatory dossier.

Early Detection of Safety Issues
Histopathology testing is conducted in preclinical studies, allowing for the early detection of potential safety issues. This early identification enables adjustments to be made in drug development plans before entering human clinical trials.

Ethical Considerations
Histopathology testing addresses ethical considerations by ensuring a thorough evaluation of potential risks to study participants and providing a basis for informed decision-making in drug development.

In summary, histopathology testing is integral to the safety assessment of a drug candidate in the IND application process. It provides detailed information on the structural changes induced by the drug, facilitating risk assessment, regulatory compliance, and informed decision-making in advancing the drug through clinical development.
 

Routine Preparation of Paraffin Embedded Sections

The routine preparation of paraffin-embedded sections is a standard histopathological technique used to examine tissues at the microscopic level. This process involves several steps to ensure that tissue samples are preserved, embedded in paraffin wax, and then sectioned for microscopic examination.

Here is an overview of the routine preparation of paraffin-embedded sections:

Tissue Fixation
The process begins with the collection of tissue samples. These samples are immediately fixed in a suitable fixative solution, such as formalin. Fixation helps preserve the cellular structure and prevents tissue degradation.

Dehydration
After fixation, the tissues are dehydrated using a series of graded alcohol solutions. Dehydration removes water from the tissues and prepares them for infiltration with paraffin wax.

Clearing
Tissues are then cleared using a clearing agent, such as xylene. This step removes the alcohol and further dehydrates the tissues while rendering them transparent

Infiltration with Paraffin
Tissues are immersed in molten paraffin wax. The paraffin infiltrates the tissue, replacing the clearing agent. This step ensures that the tissue becomes impregnated with paraffin, allowing for easy sectioning.

Embedding
The infiltrated tissues are placed in molds, and additional paraffin is added. Once the paraffin solidifies, it forms a block with the tissue embedded within. The block is then trimmed to expose the tissue surface.

Sectioning
The paraffin-embedded block is mounted on a microtome, and thin sections (usually around 4 to 5 micrometers thick) are cut from the block. These sections are then collected on glass slides.

Floating on a Water Bath
The sections are floated on a warm water bath. The heat helps the sections to flatten and adhere to the glass slides.

Drying
The slides with attached tissue sections are allowed to dry, ensuring that the sections adhere firmly to the slides.

Mounting
Once dry, the sections are mounted on glass slides. A mounting medium, such as a resinous or aqueous medium, is applied to the sections to protect them and facilitate microscopic examination.

Staining
The mounted sections are then subjected to various staining techniques, such as hematoxylin and eosin (H&E) staining. Staining enhances the contrast and allows for the visualization of different cellular structures.

Cover Slipping
After staining, a coverslip is applied to the section using a mounting medium. The coverslip protects the stained section and facilitates optical clarity during microscopic examination.

Microscopic Examination
The prepared slides are examined under a microscope by a pathologist or histotechnologist to assess the tissue morphology and identify any pathological changes.

Histopathological Analysis
The histopathologist analyses the stained sections to make diagnostic assessments, identify abnormalities, and provide information for research or clinical purposes.

Documentation and Reporting
The findings from the histopathological analysis are documented in a report, which is an essential component of diagnostic pathology or research studies.

This routine preparation of paraffin-embedded sections is a standardised and essential process in histopathology, enabling the detailed examination of tissues for diagnostic and research purposes. It allows pathologists to visualise cellular structures and identify abnormalities or diseases at the microscopic level.
 

Slide and Cassette Printing


In the context of histopathology testing, slide and cassette printing are processes used to label and track individual tissue specimens throughout the histopathological workflow. These processes involve the application of unique identifiers, such as specimen numbers, barcodes, or other information, onto glass slides and cassettes that hold tissue samples. The primary purpose of slide and cassette printing is to ensure proper identification, traceability, and organisation of specimens during tissue processing, staining, and microscopic examination.

Here's an overview of slide and cassette printing in histopathology:

Slide Printing:

Purpose
Slide printing is performed to label individual glass slides that will hold thin tissue sections for microscopic examination.

Identification Information
Information printed on slides typically includes a unique specimen identifier, patient information (e.g., accession number or patient ID), and any other relevant details.

Methods
Slide printing can be done using various methods, including direct printing using a specialised printer that applies ink or a laser to the slide surface. Alternatively, adhesive labels with printed information can be affixed to the slides.

Barcode Integration
Barcodes are often incorporated into slide printing for automated tracking and data management systems. Barcoded slides streamline the identification process and reduce the risk of errors.

Slide Label Placement
Labels are usually placed on the frosted end of the slide, leaving the transparent portion unobstructed for viewing the tissue section under the microscope.

Cassette Printing:

Purpose
Cassette printing is carried out to label the plastic cassettes that hold tissue specimens during tissue processing steps, such as fixation, dehydration, and embedding in paraffin wax.

Identification Information
Information on cassettes typically includes the same details as slide printing, such as a unique specimen identifier and patient information. Additional information may include the type of tissue and any relevant processing instructions.

Methods
Cassette printing can be done using printers equipped with specialised ink or laser technology. Barcodes are often integrated into cassette labels for efficient tracking.

Durable Printing
Labels on cassettes need to be durable and resistant to chemicals used during tissue processing. Printing methods ensure that the information remains legible throughout the entire histopathological workflow.

Integration with Laboratory Information System (LIS)
Information on cassettes is often integrated into the laboratory information system (LIS), allowing for seamless tracking and documentation of each specimen's journey through the histopathology laboratory.

Importance of Slide and Cassette Printing:

Sample Traceability
Slide and cassette printing ensures that each tissue sample is uniquely identified, providing traceability from the moment of collection to the final microscopic examination.

Error Reduction
The use of printed labels and barcodes reduces the likelihood of manual errors in specimen identification, enhancing the accuracy and reliability of histopathological results.

Efficiency in Workflow
Automated tracking systems with printed labels contribute to the efficiency of the histopathological workflow by streamlining specimen handling and processing.

Data Integration
Information from printed labels can be integrated into laboratory information systems, facilitating data management and providing a comprehensive record of each specimen.

Compliance with Regulations
Proper specimen labeling is essential for compliance with regulatory requirements and accreditation standards in pathology laboratories.

Slide and cassette printing are critical components of the histopathological process, contributing to the accurate and efficient handling of tissue specimens. These processes help ensure that each specimen is appropriately identified, tracked, and documented throughout its journey in the laboratory.
 

100% Microscopic Review for Section Quality

In the context of histopathology testing, a "100% microscopic review for section quality" refers to a thorough examination of all tissue sections on a glass slide under a microscope to assess the quality of the prepared sections. This process is a part of the quality control measures in histopathology laboratories and is particularly important in ensuring the accuracy and reliability of pathological diagnoses.

Here's an explanation of this concept:

1. Microscopic Review
After the tissue sections are prepared, stained, and mounted on glass slides, a pathologist or histotechnologist conducts a microscopic review. This involves examining the tissue sections using a microscope to assess cellular morphology, staining quality, and overall section integrity.

2. 100% Review
The term "100% review" indicates that every single tissue section on a particular slide is examined, leaving no section unassessed. This comprehensive approach is employed to minimize the risk of overlooking any abnormalities or issues that may be present in the tissue sample.

3. Section Quality Assessment:
The primary focus of the microscopic review for section quality is to ensure that the tissue sections meet the required standards for accurate pathological interpretation. Key aspects assessed during this review may include:

  • Cellular Morphology: Ensuring that cells are well-preserved and display normal or abnormal characteristics as expected.
  • Staining Quality: Verifying that the staining, especially with hematoxylin and eosin (H&E), is optimal for visualizing cellular structures.
  • Uniformity: Checking for uniformity in section thickness and staining across the entire slide.
  • Artifact Detection: Identifying and addressing any artifacts or processing-related issues that may affect the interpretability of the tissue sections.

4. Quality Control Measures
The 100% microscopic review for section quality is a quality control measure to catch any discrepancies or potential problems early in the histopathological workflow. It helps ensure that the final slides submitted for diagnosis meet high-quality standards.

5. Documentation
Findings from the microscopic review are typically documented. Any concerns or observations regarding section quality are noted, and appropriate actions may be taken, such as repeating certain steps in the tissue processing or staining protocol.

6. Quality Assurance in Diagnostics
For diagnostic purposes, ensuring the quality of tissue sections is crucial. An accurate diagnosis relies on the pathologist's ability to visualize and interpret the cellular and tissue structures present in the sections.

7. Continuous Improvement
Feedback from the microscopic review process can contribute to continuous improvement in laboratory techniques and procedures. Any identified issues can lead to adjustments in the processing workflow to enhance overall quality.

8. Regulatory Compliance
Histopathology laboratories follow guidelines and regulations that require rigorous quality control measures. The 100% microscopic review aligns with these standards to maintain compliance.

In summary, the "100% microscopic review for section quality" is a comprehensive examination of all tissue sections on a glass slide under a microscope to ensure the highest standards of quality in histopathology testing. This meticulous review is a critical step in the quality assurance process, contributing to the accuracy and reliability of pathological diagnoses.