The variable responding scale for detection of random responding on the multidimensional pain inventory

This study developed a scale for detecting random responding on the Multidimensional Pain Inventory (MPI). Ninety-five undergraduates (derivation sample) completed the MPI randomly, as did 2 cross-validation samples, 34 chronic pain patients (pain) and 115 health care professionals (health care). Up to 71% of random profiles appeared valid. For comparison in validity scale development, a clinical MPI sample (N = 507) was split into derivation and cross-validation samples. Given that responses to similar items should be consistent in nonrandom protocols, 8 pairs of highly intercorrelated items were selected. Absolute differences between pairs were summed into a variable responding (VR) scale; scores were contrasted across clinical and random groups. On the basis of derivation sample results, VR scale cut scores (from 12 to 17) were tested and found to discriminate accurately (p < .001) between the cross-validation clinical and the healthcare and pain random responding samples. The potential clinical utility of the VR scale to identify random MPI protocols is supported.