Prospective Comparative Study of Electronic Visual Analogue Scale and Verbal Numerical Rating Scale in Acute Post-operative Pain.

When assessing acute post-operative pain, the validity, reproducibility and reliability of Visual Analogue Scale (VAS) and verbal Numerical Rating Scale (NRS) have been investigated extensively. The use of electronic version of VAS has been published in the recent 10 years yet publication related to its use in pain medicine were few. Jamison et al have shown good correlation between electronic VAS vs paper VAS on healthy volunteers using weight as the stimulus. In normal subjects as well as fibromyalgia patients, electronic form of VAS could be used to describe different levels of experimental heat stimulation.

Long term study had been done where electronic pain diary were compared against paper diary in recording pain in 36 patients with chronic low back pain. The 2 scales showed good correlation. This author use a software that is Palm-top computer based. Following these few studies, validation study in chronic pain patient were published. A Palm-top computer based VAS was compared with paper NRS in 200 chronic pain patients. The pain level recorded by the two methods were considered equivalent by the author. However, Palm-top computer has almost disappeared from the market nowadays.

Recent handheld electronic devices (iPad®) were incorporated with touch screen input interface which allow users to use their finger as the input device. To our knowledge, there is no published data concerning iPad-based VAS, especially in post-operative pain. We would like to compare the data obtained from electronic VAS on iPad with verbal numerical rating scale when acute post-operative pain is assessed.

Hypothesis The null hypothesis is that the two pain measurement method do not correlate. The Spearman correlation coefficient between electronic VAS and verbal NRS will be reported.