Convergent validity evidence for the Pain and Discomfort Scale (PADS) for pain assessment among adults with intellectual disability.

OBJECTIVES: The main aim of the study was to generate initial convergent validity evidence for the Pain and Discomfort Scale (PADS) for use with nonverbal adults with intellectual disabilities. MATERIALS AND METHODS: Forty-four adults with intellectual disability (mean age=46, 52% male) were evaluated using a standardized sham-controlled and blinded sensory testing protocol, from which Facial Action Coding System (FACS) and PADS scores were tested for (1) sensitivity to an array of calibrated sensory stimuli; (2) specificity (active vs. sham trials); and (3) concordance. RESULTS: The primary findings were those participants who were reliably coded using both FACS and PADS approaches as being reactive to the sensory stimuli (FACS: F(2,86)=4.71, P<0.05, PADS: F(2,86)=21.49, P<0.05) (sensitivity evidence), not reactive during the sham stimulus trials (FACS: F(1,43)=3.77, P=0.06, PADS: F(1,43)=5.87, P=0.02) (specificity evidence), and there were significant (r=0.41 to 0.51, P<0.01) correlations between PADS and FACS (convergent validity evidence). DISCUSSION: FACS is an objective coding platform for facial expression. It requires intensive training and resources for scoring. As such it may be limited for clinical application. PADS was designed for clinical application. PADS scores were comparable with FACS scores under controlled evaluation conditions providing partial convergent validity evidence for its use.

Evaluating a sham-controlled sensory-testing protocol for nonverbal adults with neurodevelopmental disorders: self-injury and gender effects.

UNLABELLED: Ambiguous or blunted responses to sensory and painful stimuli among individuals with severe intellectual disabilities and comorbid communicative impairments put them at risk for having their experience of pain discounted and their expression of pain misinterpreted. Valid measurement procedures of behavioral expression are critical for this vulnerable group of individuals. We investigated a sham-controlled sensory-testing protocol as an approach to guard against observer bias during nonverbal behavioral recording for individuals with intellectual disabilities. Participants were 44 (52% male) adults (mean age = 46, sd = 10) with moderate (14%) and severe to profound (86%) intellectual impairment. The facial behavior of the participants before, during, and after 5 sensory-stimulation modalities (pin prick, light touch, deep pressure, cool, warm) was coded by 3 raters using the Facial Action Coding System (FACS). For each participant, the 5 active sensory trials were randomized with sham trials during which no stimulation was applied. Observers were blinded to active vs sham stimulation status. FACS scores increased significantly during active sensory trials (P < .05) compared with sham trials. There were significant effects for gender, with females more expressive than males (P < .05). There were also significant effects for the presence of self-injurious behavior (SIB), with individuals with SIB more expressive than individuals without SIB (P < .05). The results suggest that the procedure was valid (ie, distinguished between active vs sham sensory stimulation) and provides additional evidence that individuals with significant intellectual impairments are sensitive to tactile stimulation consistent with quantitative sensory-testing protocols. PERSPECTIVE: This article presents a novel application of a modified approach to quantitative sensory testing for nonverbal adults with intellectual and developmental disabilities. This approach could be important in helping determine sensory issues related to tactile and nociceptive processes among a highly vulnerable group of individuals.

Evidence of increased non-verbal behavioral signs of pain in adults with neurodevelopmental disorders and chronic self-injury.

The role of pain in relation to self-injurious behavior (SIB) among individuals with intellectual disabilities is not well understood. Some models of SIB are based on altered endogenous opioid system activity which could result in elevated pain thresholds. In this study, non-verbal behavioral signs indicative of pain as measured by the Non-Communicating Children's Pain Checklist (NCCPC) were compared between matched individuals with (N=35) and without (N=35) chronic self-injurious behavior (SIB) and neurodevelopmental disorders. Significant (p<.01) between group differences (SIB Group>Control Group) were found for the NCCPC Total Score, and for the Vocal, Social/Personality, and Eating/Sleeping subscales of the NCCPC. These results are not consistent with models of SIB in which pain sensitivity is assumed to be attenuated because of opioid system activity and are suggestive of intact and possibly amplified pain expression.