Harnessing historical data to derive reference limits - A comparison of e-norms to traditionally derived reference...

Area of Science:

• Clinical Neurophysiology
• Biostatistics

Background:

• Nerve conduction studies (NCS) are crucial for diagnosing neurological disorders.
• Accurate reference limits are essential for interpreting NCS results.
• Traditional derivation of reference limits requires extensive data collection from healthy individuals.

Purpose of the Study:

• To further develop and validate the extrapolated norms (e-norms) method for deriving NCS reference limits.
• To compare e-norms derived limits with traditional reference limits in pediatric and adult populations.
• To assess the viability of using historical laboratory datasets for generating NCS reference limits.

Main Methods:

• The e-norms method was applied to historical NCS datasets.
• Reference limits were calculated using ±2 SD and ±2.5 SD.
• Results were compared against reference limits derived from healthy control groups (65 children, 578 adults).
• Five common nerves were analyzed for amplitudes, conduction velocities, and F-waves.

Main Results:

• The e-norms method (mean ±2 SD) produced slightly stricter reference limits than traditional methods.
• Adjusting the e-norms range to mean ±2.5 SD improved pediatric results and slightly overcorrected in adults.
• Average agreement between e-norms and traditional methods was 95% (±2 SD) and 96% (±2.5 SD).

Conclusions:

• The adapted e-norms method reliably replicates traditionally derived NCS reference limits.
• The method is suitable for analyzing large historical NCS datasets, reducing bias and improving rating accuracy.
• E-norms offer a viable alternative for generating reference limits, especially when new data collection is impractical.