Sensory testing with point of folded paper - a comparison with standardized nylon monofilaments

Background: Semmes -Weinstein monofilaments are ideal for sensory testing, however they are not freely available. An effective, cheap method for sensory testing, without risk of disease transmission, would be ideal for field clinics in developing countries. Kumarasinghe (2001) introduced use of point of folded paper for sensory testing in leprosy patients.

Aims: 1. To test efficacy of point of folded paper as a tool for sensory testing, compared to nylon monofilament (NMF) in the Neuropen^R (Owen Mumford, Oxon, UK) 2. To compare 45 gsm (grammes per sq. metre) paper and 80 gsm paper as a tool for sensory testing compared to the NMF.

Methods: Part I: 80 gsm and 45 gsm paper were used. A4-size paper (270x297 mm) was cut into 4 equal parts, and each was folded twice and creased to give a sharp point. Healthy volunteer medical students were recruited. They were requested firstly to say whether they feel touch/ pressure with the 3 different materials, and then compare the sensations of points of 45 gsm and 80 gsm folded paper with the Neuropen NMF. Volar aspect of forearms was tested separately. Subjects were blinded, and same observer carried out tests. Paper points were pressed lightly, perpendicular to skin, as in the case of NMF. Subjects were requested to state whether the sensory testing methods were 'not different', 'slightly different', or 'totally different'.

Part II: Ten consecutive patients diagnosed as tuberculoid (TT) and borderiine tuberculoid (BT) leprosy, attending Dermatology Clinic at Colombo North Teaching Hospital, were tested separately with monofilament of Neuropen and point of twice-folded, ordinary prescription paper (45 gsm). Patients were blinded to the device used each time for testing sensations within and outside the hypopigmented patches.

Results: Part I: There were 80 (55.2%) males and 65 (44.8%) females (n=145). Mean age was 23.9 yrs (range 21-27 yrs). All subjects said that touch/pressure was felt with all three materials (NMF, 45 gsm, and 80 gsm paper). In the comparison of 45 gsm paper with NMF, 56.5% stated that sensation was 'not different', 42.7% said 'slightly different', and only 0.68% said sensation was 'totally different'. When 80 gsm paper and NMF were compared, 30.3% stated that it was 'not different', 66.2% said 'slightly different', and only 3.4% said that it was 'totally different'.

Part II: In all 10 patients (6 M, 4 F, 22-60 years) tested, both NMF and paper points were able to elicit the appropriate responses by patients about the area of sensory impairment. Sensory impairment elicited correlated with the lesions of leprosy.

Conclusions: Sensory testing with point of folded paper is a suitable alternative to standardized NMF. 45 gsm paper point was more closely comparable to the NMF than 80 gsm paper. Sensory testing on leprosy patients with sensory impairment confirmed that it can be used successfully in leprosy patients as well. Sensory testing with point of paper would be valuable in field clinics in developing countries where suitable NMF are not available.