Comparison of Electron Microscopy vs. Light Microscopy for Diagnosing GERD in Patients with Refractory Heartburn

Abstract

Purpose: In patients with ongoing heartburn despite acid suppression with PPIs, especially in the absence of endoscopic changes, the diagnosis of GERD is challenging and often requires prolonged reflux monitoring. Histological changes attributed to reflux in esophageal biopsies examined by light microscopy (LM) are suboptimal for diagnosing GERD. Dilation of intercellular space distance (ISD) in esophageal epithelium assessed by electron microscopy (EM) is emerging as a robust marker of GERD. Our aim was to compare the sensitivity and specificity of EM vs. LM for the diagnosis of GERD in patients with persistent heartburn despite PPI. Methods: Patients with persistent heartburn despite PPI BID underwent 24 hr-hr ambulatory impedance-pH (MII-pH), and endoscopy (EGD) with biopsies 5 cm above the Z line for analysis by EM and LM. Two schemes with different rigor used to diagnose GERD: “rigorous criteria” were esophagitis on EGD or abnormal MII-pH defined by increased esophageal acid exposure; “less rigorous criteria” added positive symptom index (>50% symptoms associated with reflux) to definition GERD. In both schemes, functional heartburn patients (FH) had normal EGD and MII-pH. Intercellular space distance (ISD) determined blindly by EM at 5,000 magnification using computer-assisted morphometry (Image J software). 10 ISD measurements taken in each of 10 micrographs, mean ISD was the average of 100 measurements. Upper limit of normal ISD was 0.68 μm (the 95th percentile ISD in ten healthy volunteers with normal pH-metry). Light microscopy evaluation performed by single, blinded gastrointestinal pathologist after routine hematoxylin and eosin staining, who provided a diagnosis of GERD based on rete papillae elongation or basal cell hyperplasia. The sensitivity and specificity of EM and LM for GERD were then compared. Results: Use of the more rigorous EGD/MII-pH criteria yielded 6 GERD and 16 FH patients; sensitivity and specificity were 83% and 88% for EM, 67% and of 44% for LM. The less rigorous criteria yielded 12 GERD and 10 FH patients; sensitivity and specificity were 58% and 100% for EM, 67% and 50% for LM. Specificity for GERD appears good for EM and poor for LM. Sensitivity is fair and comparable for EM and LM using less rigorous criteria for GERD, sensitivity is better for EM compared to LM when using more stringent criteria. Conclusion: Increased intercellular space distance measured by Electron Microscopy has good specificity and is thus very reliable (and superior to LM) for excluding GERD in patients with refractory heartburn, providing good accuracy for the diagnosis of functional heartburn. EM has good sensitivity, especially in patients with GERD diagnosed by more rigorous criteria.