Counting Intraepithelial Lymphocytes: A Comparison Between Routine Staining and CD3 Immunohistochemistry

Area of Science:

• Gastroenterology
• Histopathology
• Immunohistochemistry

Background:

• Intraepithelial lymphocytes (IELs) are crucial for duodenal biopsy assessment.
• Hematoxylin and eosin (H&E) and CD3 immunohistochemistry (IHC) are used for IEL counting.
• Comparability of IEL counts between H&E and CD3 IHC is not well-established.

Purpose of the Study:

• To compare IEL counts in duodenal biopsies using H&E stains versus CD3 IHC.
• To evaluate interobserver variability in IEL counting with both methods.

Main Methods:

• Thirty-five paired H&E and CD3 stained duodenal biopsy sections were analyzed.
• Six pathologists counted IELs per 100 enterocytes.
• Counts were categorized into normal, mildly raised, and markedly raised groups.

Main Results:

• CD3 IHC demonstrated significantly higher IEL counts compared to H&E.
• Four cases with normal H&E counts showed elevated counts with CD3 IHC.
• Moderate interobserver agreement was observed for both H&E and CD3 methods.
• CD3 IHC did not significantly improve interobserver variability.

Conclusions:

• IEL counts obtained by CD3 IHC and H&E staining are not directly comparable.
• The distinct results suggest these methods should not be considered equivalent for IEL quantification.
• Clinical interpretation of IEL counts may require method-specific reference ranges.