(004) Correlations Between Immunohistochemical Staining and Pain-Related Assessments in Patients with Neuroproliferative Vestibulodynia
Authors: Kim NN , Goldstein I , Goldstein SW , Drian A , Yee A 
Published: February 2024

Abstract

Introduction
A clinically suspected diagnosis of neuroproliferative vestibulodynia (NPV) can be confirmed by examining immunohistochemical (IHC) staining of excised vestibular specimens. Compared to controls, specimens from NPV patients have been found to contain &gt;8 mast cells per high-power field (HPF) and increased density of nerves.

Objective
To assess for correlations between patient reported pain-related measures and computer-assisted histometry of excised vestibulectomy specimen IHC staining with CD117 (marker for mast cells) and PGP9.5 (marker for nerves) in a cohort of histopathologically confirmed NPV patients.

Methods
Patients (n=65) with lifelong or acquired NPV undergoing vestibulectomy had IHC-staining of the vestibular tissue. Tissue sections from the 1:00-11:00 and/or 12:00 regions of the vestibule were examined and high-resolution images were captured using a microscope at 100x and 200x magnification. A minimum of 2 photomicrographs per magnification were taken for each tissue section that included epithelial basement membrane and adjacent subepithelium representative of the majority of immunostained tissue. Fractional area of positive immunostaining of all photomicrographs was determined using computer-assisted histometry by ImageJ. Mean fractional area was determined from 3 separate measurements of each photomicrograph. Correlations were made between density of IHC staining and the following assessments: pain domain of the Female Sexual Function Index (FSFI), the Short Form McGill Pain Questionnaire (SF-MPQ), and cotton-tipped swab testing. We also examined correlations with the Patient Global Impression of Improvement (PGI-I), a treatment response index and indirect assessment of pain. Data were analyzed using Spearman correlations and the Mann-Whitney test.

Results
While all patients reported high levels of pain, there were no correlations between CD117- or PGP9.5-immunopositive mean fractional area and FSFI pain domain or SF-MPQ scores. There was no difference in immunopositive mean fractional area between lifelong and acquired NPV. A positive correlation between fractional area of CD117 immunostaining in the 1:00-11:00 region of the vestibule and cotton-tipped swab test pain score approached but did not reach statistical significance (r = 0.24, p = 0.063). Fractional area of PGP9.5 immunostaining was negatively correlated with PGI-I scores (r = -0.50, p = 0.006) in the 1:00-11:00 region of the vestibule. Lower PGI-I scores are indicative of greater improvement after surgical intervention. No other correlations were observed between immunostaining and PGI-I or cotton-tipped swab testing scores. Likewise, SF-MPQ domain scores had no correlation to PGI-I or cotton-tipped swab testing. Median cotton-tipped swab testing pain scores were significantly higher (p &lt; 0.001) in patients with lifelong NPV (7.6) compared to those with acquired NPV (5.7).

Conclusions
The lack of correlations between immunopositive staining and multiple pain-related assessment scores suggests a non-linear threshold for mast cell accumulation and nerve proliferation that produces pain symptoms for all NPV patients. Cotton-tipped swab pain scores were more closely associated with density of CD117 immunostaining, while clinical improvement in pain symptoms was significantly correlated with density of PGP9.5 immunostaining. The fact that patients with lifelong NPV had significantly more pain on cotton-tipped swab testing than the acquired NPV subgroup may be related to duration of the condition.

Disclosure
No.