F-minimum latency, F-maximum latency and F-estimate as early markers of neuropathy in type 2 diabetes mellitus: a...

Diabetic peripheral neuropathy is a frequent and disabling complication of type 2 diabetes mellitus (T2DM). Early identification of subclinical neuropathy is crucial to prevent progression. F-wave parameters, by assessing proximal and distal motor pathways, may serve as sensitive indicators of early nerve dysfunction.

To evaluate F-wave parameters in patients with T2DM and analyse their relationship with clinical neuropathy severity (Michigan Neuropathy Screening Instrument-MNSI and Vibration Perception Threshold-VPT) and metabolic control indices.

This hospital-based cross-sectional study included 226 participants (184 diabetics and 42 non-diabetic controls). All subjects underwent detailed clinical evaluation, biochemical profiling, neuropathy assessment using MNSI and VPT, and electrophysiological testing including F-wave analysis of the tibial nerve. Parameters studied were F-min latency, F-max latency, chronodispersion, F-estimate, F-wave/M-wave (F/M) amplitude ratio and persistence. Comparisons were made among three groups-non-diabetic controls, diabetics without neuropathy and diabetics with neuropathy. Correlation and receiver operating characteristic (ROC) analyses were performed to assess diagnostic and predictive utility.

F-min, F-max and F-estimate latencies were significantly prolonged in diabetic subjects compared with controls (p<0.001), with stepwise worsening from non-diabetic to neuropathic groups. Chronodispersion showed minor, non-significant change, and F/M amplitude ratio exhibited mild elevation in diabetics (p<0.05). F-wave persistence remained comparable across groups. Significant positive correlations were observed between F-min latency and VPT (r=0.424, p<0.001), MNSI score (r=0.198, p=0.012) and glycated haemoglobin (HbA1c) (r=0.366, p=0.031). ROC analysis identified F-min latency (area under the curve, AUC=0.729) and F-max latency (AUC=0.710) as the most accurate discriminators for neuropathy.

Prolonged F-wave latencies, particularly minimum latency and F-estimate, are sensitive markers of early motor nerve involvement in T2DM. These parameters correlate with clinical and metabolic indices of neuropathy and can enhance detection of subclinical diabetic neuropathy when routine nerve conduction studies are normal.