Aanem Technology Review Establishing High-quality Reference Values for Nerve Conduction Studies: a Report from the Normative Data Task Force of the American Association of Neuromuscular & Electrodiagnostic Medicine

Introduction: There are not uniform standards for nerve conduction testing across the United States. The objective of this study is to present a set of methodologically sound criteria to evaluate the literature for the purpose of identifying high-quality normative nerve conduction studies (NCS) suitable for widespread use. Methods: The Normative Data Task Force (NDTF) was formed to review published studies on methodological issues related to NCS. A set of criteria was then developed to evaluate the literature. These criteria and their rationale are described. Results: We identified 7 key issues that reflect high quality in NCS. For each issue, specific review criteria were developed. Conclusion: Rigorous criteria enable identification of high-quality studies dealing with nerve conduction reference values. This represents the first step toward the overarching goal of recommending NCS techniques and reference values for electrodiagnostic medicine. Muscle Nerve 54: 366–370, 2016 Electrodiagnostic (EDx) medicine has been in existence since the 1940s. EDx physicians and technologists perform nerve conduction studies (NCS) and needle electromyography to evaluate disorders of the peripheral nervous and musculoskeletal systems. In the past few decades, EDx instrumentation and signal processing have benefitted greatly from technological advancements in computing and electronics. The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) has been involved in standardizing how the specialty is practiced through publication of guidelines and practice parameters. The recent accreditation of EDx laboratories is one step in standardizing and defining quality care across the field. However, there is no universal standard for NCS in the United States. Individual laboratories have historically been encouraged to derive their own reference values despite inherent methodological and statistical challenges with this approach. The majority of EDx physicians and laboratories, rather than develop their own reference values, instead rely on the peerreviewed literature, textbooks, or reference values generated by academic training programs. However, many published studies do not meet contemporary standards for statistical and methodological rigor. Performing NCS on nerves and deciding whether the results fall within an expected range of normal values with a statistical level of precision is fundamental to EDx medicine. Lack of NCS standardization diminishes reliability and consistency in identification of pathology. Such concerns were demonstrated in a recent study that assessed intraand interobserver reliability when patients with diabetic sensorimotor polyneuropathy were evaluated. There was a 37.5% difference in the interobserver judgment of individual nerves as being normal, which was attributed to variability in the performance of NCS and in the use of varied reference values. This variability was of sufficient magnitude to be a concern for therapeutic trials. One recommendation to improve interrater reliability in therapeutic trials Abbreviations: AANEM American Association of Neuromuscular & Electrodiagnostic Medicine, EDx, electrodiagnostic; MSE, mean square error; NCS, nerve conduction studies; NDTF, Normative Data Task Force; SNAP, sensory nerve action potential