Intravenous angiocatheters as a novel alternative to Semmes-Weinstein monofilament evaluation in testing protective sensation

Semmes-Weinstein monofilament (SWM) evaluation for protective sensation in diabetic feet is a widely used tool to guide patient care. Little evidence is available for alternative testing modalities for use when monofilament is not available or is deformed. Multiple varieties of intravenous angiocatheter tubing were subjected to biomechanical testing on a digital scale to assess the force generated once bending was observed by five independently tested raters. A 5.07 SWM (10 g) was tested in similar manner to establish a baseline and validate testing methodology. The 24 gauge × 0.75 in angiocatheter measured the closest to the 5.07 SWM (10 g) at an average force of 22 ± 0.91 g compared with 10.2 ± 0.13 g. Large-gauge angiocatheters measured greater forces. High intra-rater and inter-rater reliability was observed with all values greater than 0.98 (p < 0.001). A 24 gauge × 0.75 in angiocatheter tubing can be used as an alternative to the standard 5.07 SWM (10 g) for testing protective sensation in diabetic feet. Reviewing previously published receiver operating characteristics, this modality would yield estimated sensitivity and specificity values greater than 0.8 and 0.7, respectively, for detecting insensate feet tested at the bilateral metatarsal heads.