Sural nerve biopsy utility by masked assessment of individual histologic preparations

Abstract

Background and Aims Comprehensive study of sural nerve biopsy utility based on individual histopathologic preparations is lacking. We aimed to quantify the value of different histologic preparations in diagnosis. Methods One hundred consecutive sural nerves were studied by standard histological preparations plus graded teased nerve fibers (GTNF), immunohistochemistry, and epoxy‐semithin morphometry. Three examiners scored the individual preparations separately by a questionnaire of neuropathic and interstitial abnormalities, masked to the biopsy number, versus a gold‐standard of all preparations. Multivariate modeling was utilized to determine best approach versus the gold‐standard. Results Highest confidence (range 8–9 of 10) and inter‐rater reliability (99%) for fiber abnormalities came from GTNF, and interstitial abnormalities from paraffin stains (range 7–8, 99%). Vasculitic neuropathy associated with GTNF axonal degeneration (moderate to severe 79%) with OR 3.8, 95% CI (1.001–14.7), p = .04, but not significantly with the other preparations. Clinicopathologic diagnoses associated with teased fiber abnormalities in chronic inflammatory demyelinating polyradiculoneuropathy, 80% (8/10); amyloidosis, 50% (1/2); adult‐onset polyglucosan disease 100% (1/1). GTNF and paraffin stains significantly correlated with fiber density determined by morphometric analysis (GTNF: OR 9.9, p < .0001, paraffin: OR 3.8, p = .03). GTNF combined with paraffin sections had highest accuracy for clinicopathologic diagnoses and fiber density with 0.86 C‐stat prediction versus morphometric analysis. Pathological results lead to initiation or changes of immunotherapy in 70% (35/50; initiation n = 22, reduction n = 9, escalation n = 4) with the remaining having alternative intervention or no change. Interpretation Nerve biopsy paraffin stains combined with GTNF have highest diagnostic utility, confidence, inter‐rater reliability, improving accuracy for a pathologic diagnosis aiding treatment recommendations. Immunostains and epoxy preparations are also demonstrated useful supporting consensus guidelines. This study provides class II evidence for individual nerve preparation utility.

Application of Several Special Staining Methods for Paraffin Sections on Epon-Embedded Semithin Sections

“…In these studies, quantitative histomorphometric analyses were performed by evaluating the myelinated nerve fiber density (17)(18)(19)(20)(21). These sections are also used in the evaluation of demyelination and remyelination levels according to the results of G-ratio (the ratio of axon diameter and myelin sheath thickness) after damage, lesion, and treatments in the central nervous system (22).…”