Can We 'Predict' Long-Term Outcome for Ambulatory Transcutaneous Electrical Nerve Stimulation in Patients with Chronic Pain?

Background Evidence for effectiveness of transcutaneous electrical nerve stimulation ( TENS) is still inconclusive. As heterogeneity of chronic pain patients might be an important factor for this lack of efficacy, identifying factors for a successful long-term outcome is of great importance. Methods A prospective study was performed to identify variables with potential predictive value for 2 outcome measures on long term (6 months); (1) continuation of TENS, and (2) a minimally clinical important pain reduction of ≥ 33%. At baseline, a set of risk factors including pain-related variables, psychological factors, and disability was measured. Results In a multiple logistic regression analysis, higher patient's expectations, neuropathic pain, no severe pain (< 80 mm visual analogue scale [ VAS]) were independently related to long-term continuation of TENS. For the outcome 'minimally clinical important pain reduction,' the multiple logistic regression analysis indicated that no multisited pain (> 2 pain locations) and intermittent pain were positively and independently associated with a minimally clinical important pain reduction of ≥ 33%. Conclusion The results showed that factors associated with a successful outcome in the long term are dependent on definition of successful outcome. [ABSTRACT FROM AUTHOR]