Detecting malingered pain-related disability: classification accuracy of the Portland Digit Recognition Test.

This study used criterion groups validation to determine the classification accuracy of the Portland Digit Recognition Test (PDRT) at a range of cutting scores in chronic pain patients undergoing psychological evaluation (n = 318), college student simulators (n = 29), and patients with brain damage (n = 120). PDRT scores decreased and failure rates increased as a function of greater independent evidence of intentional underperformance. There were no differences between patients classified as malingering and college student simulators. The PDRT detected from 33% to nearly 60% of malingering chronic pain patients, depending on the cutoff used. False positive error rates ranged from 3% to 6%. Scores higher than the original cutoffs may be interpreted as indicating negative response bias in patients with pain, increasing the usefulness and facilitating the clinical application of the PDRT in the detection of malingering in pain.