Could Pancreatic Islet Transplantation Outcome Be Impacted by Overestimating Islet Volume? Insights From a Serial Section Study.

Introduction: The outcome of pancreatic islet transplantation surgery is influenced by factors like islet volume, purity, and dimensions. Single paraffin section measurement may underestimate islet diameter. Researchers have identified limitations in measuring islet equivalent quantity. This study quantified maximum islet diameter using serial sections and compared it with paraffin sections. We also evaluated actual islet volume and compared it with IEQ based on diameter measurements. Materials and Methods: This study utilized pancreatic tissue from six adult human samples. Serial sections were stained immunohistochemically using anti-synaptophysin antibody. Islets were identified and measured using serial sections to determine their diameter and volume. The maximum average diameter across sections was used to calculate the islet diameter. Islet volume was calculated by summing areas across sections and correcting for section thickness and interval. We compared the calculated IEQ based on the diameter and volume. Results: The study revealed significant discrepancies between pancreatic islet diameter measured from single paraffin sections and those determined from serial sections. The mean sectional diameter was 23.37% smaller than the actual diameter (p < 0.0001), with larger islets showing a more significant underestimation. IEQ based on diameter was overestimated by 87.51% compared to IEQ based on actual volume, with large islets contributing significantly to this discrepancy (111.7%). Conclusions: Single paraffin section analyses underestimate islet dimensions, especially for islets > 125 μm in diameter. Using conversion factors from this study provides accurate size assessments. To enhance transplantation accuracy, it is essential to use robust size calculations rather than binning. Using the islet diameter tends to overestimate their volume, particularly when the islet index is ≥ 1 (as most islets are larger than 150 μm in diameter). This overestimation increases the risk of unfavorable transplantation outcomes. Thus, IEQ should be adjusted to the upper range when the islet index is ≥ 1, accounting for the potential overestimation of islet volume.