Objectives: Quantitative sensory testing is a reference method for characterization of postsurgical neuropathic components. Correct interpretation of data requires detailed information concerning the validity of the testing methods. The objective of the study was to assess the test-retest variability of thermal thresholds in patients (n=14) with the postthoracotomy pain syndrome.
Methods: Sensory mapping with a metal roller (25°C) on the surgical side delineated an area with cool sensory dysfunction. In this area and in a contralateral area, 4 prespecified sites (2.6 cm2) were outlined, in addition to the maximum pain site on the surgical side. In these total 9 sites, warmth detection threshold, cool detection threshold, and heat pain threshold were assessed.
Results: Comparisons of thermal test-retest assessments did not demonstrate any significant intraside differences. The SDs of the thermal assessments in nonpain sites and in the maximum pain site ranged from 1.9 to 2.5°C and 3.5 to 6.9°C, respectively. The estimated within-patient and between-patient variances were 5% to 28% and 72% to 95%, respectively, of the total variances. Although a generally poor test-retest agreement was demonstrated, the much lower within-patient than between-patient variances facilitated estimations of highly statistical significant, within-patient differences in thermal thresholds.
Discussion: In patients with postthoracotomy pain syndrome, several statistical methods indicated an excessively high variability in thermal thresholds, questioning the use of single quantitative sensory testing in assessments to characterize patients with chronic pain states.
*Section for Surgical Pathophysiology
†Multidisciplinary Pain Centre, Copenhagen University Hospital, Copenhagen, Denmark
The authors declare no conflict of interest. The research leading to these results is part of the Europain Collaboration, which has received support from the Innovative Medicines Initiative Joint Undertaking, under grant agreement no. 115007, resources of which are composed of financial contribution from the European Union’s Seventh Framework Programme (FP7/2007-2013) and EFPIA companies.
Reprints: Mads U. Werner, MD, DMSc, Multidisciplinary Pain Center 7612, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark (e-mail: firstname.lastname@example.org).
Received June 22, 2012
Accepted April 10, 2012