Is quantitation necessary for assessment of sural nerve biopsies?

In this study we measured the reliability and accuracy of visual assessment of certain features of sural nerve pathology. Three raters visually assessed 20 sural nerves over two sessions. Four features were categorized: (1) myelinated fiber (MF) density; (2) size loss of MFs; (3) thinly myelinated axons; and (4) axonal clusters. Intra- and interrater reliabilities for the categories were determined. Quantitative data were compared with the visual assessments. Percentage agreements for single raters between the two sessions ranged from 35% to 100% and 9 times out of 12 were > or =70%. Interrater reliability, however, showed a kappa-value range of 0.03 (poor) to 0.49 (medium). In 85% of cases, visual ratings were within one category of the quantitated MF loss. However, visual categorization was poor compared with quantitation for determining size loss of MFs and myelin thickness. Quantitation needs to be considered to aid peripheral nerve pathologists in the assessment of some of the features of sural nerve biopsy specimens.