A possible indicator of functional pain: poor pain scale correlation

The Role of Descending Pain Modulation in Chronic Primary Pain: Potential Application of Drugs Targeting Serotonergic System

Chronic primary pain (CPP) is a group of diseases with long-term pain and functional disorders but without structural or specific tissue pathologies. CPP is becoming a serious health problem in clinical practice due to the unknown cause of intractable pain and high cost of health care yet has not been satisfactorily addressed. During the past decades, a significant role for the descending pain modulation and alterations due to specific diseases of CPP has been emphasized. It has been widely established that central sensitization and alterations in neuroplasticity induced by the enhancement of descending pain facilitation and/or the impairment of descending pain inhibition can explain many chronic pain states including CPP. The descending serotonergic neurons in the raphe nuclei target receptors along the descending pain circuits and exert either pro- or antinociceptive effects in different pain conditions. In this review, we summarize the possible underlying descending pain regulation mechanisms in CPP and the role of serotonin, thus providing evidence for potential application of analgesic medications based on the serotonergic system in CPP patients.

Correlations among algometry, the visual analogue scale, and the numeric rating scale to assess chronic pelvic pain in women

Objective

To investigate the correlation between the numerical rating scale, visual analogue scale, and pressure threshold by algometry in women with chronic pelvic pain.

Study design

This was a cross-sectional study. We included 47 patients with chronic pelvic pain. All subjects underwent a pain assessment that used three different methods and were divided according to the cause of pain (endometriosis versus non-endometriosis). Moreover, we assessed the agreement between the scales (visual, analogue and algometry) using the intraclass correlation coefficient (ICC).

Results

The ICC for the numeric rating scale and the visual analogue scale regarding pain (0.992), dysmenorrhea (1.00) and dyspareunia (0.996) were strong. The agreement between the scales was excellent (p ≤0.01). The correlation between algometry and the scales showed a moderate and inverse association, and this correlation was statistically significant: as the scores on the numeric rating scale and the visual analogue scale regarding dyspareunia increased, the algometry thresholds decreased.

Conclusions

The assessment of women with chronic pelvic pain should combine pressure algometry and the numeric rating scale or the visual analogue scale, because of their inverse correlations and satisfactory reliability and sensitivity, to make pain assessment less subjective and more accurate.

Evaluation of the psychometric properties of the revised short-form McGill Pain Questionnaire

The recently revised version of the Short-Form McGill Pain Questionnaire (SF-MPQ-2) was created to assess both neuropathic and non-neuropathic pain. The current study extends prior research by testing the reliability and validity of the SF-MPQ-2 in a sample of U.S. veteran patients with a range of chronic pain diagnoses. Participants (N = 186) completed the SF-MPQ-2, a sociodemographic questionnaire, the Structured Clinical Interview for the DSM-IV, and self-report pain and psychiatric measures. Pain diagnoses were extracted from the electronic medical record. The SF-MPQ-2 total and scale scores demonstrated good-to-excellent internal consistency. Convergent and discriminant validity were supported, and SF-MPQ-2 total and scale scores increased with number of pain diagnoses and pain severity. Confirmatory factor analyses indicated that a 4-factor model fit the data better than a single-factor model. However, high intercorrelations among the 4 latent constructs were observed, and a second-order global pain construct also emerged. Overall, the SF-MPQ-2 demonstrated excellent reliability and validity in a sample of U.S. veteran patients with chronic neuropathic and non-neuropathic pain. Future psychometric studies of the SF-MPQ-2 should employ longitudinal data to evaluate the ability of scale scores to uniquely predict clinical and health service outcomes.

PERSPECTIVE

This article presents the psychometric properties of a revised version of the SF-MPQ-2. This measure may have great utility as a screening tool in clinical practice and as an outcome measure in clinical trials.

Optimizing the design of visual analogue scales for assessing quality of life: a semi-qualitative study among Chinese-speaking Singaporeans

OBJECTIVES

Current recommendations for visual analogue scale (VAS) design are largely derived from studies on pain assessment. We evaluated respondent preferences for VAS design for health-related quality of life (HRQoL) assessment.

METHODS

In-depth interviews were conducted among Chinese-speaking rheumatology outpatients and caregivers (age > or = 21 years) to determine preferences for the following: (1) VAS orientation (horizontal/vertical); (2) length of instructions (long/intermediate/short); (3) scale range (0-10/0-100 points); (4) indicator for computerized touchscreen VAS (bar/column). Responses in subjects expressing a preference were compared using tests of proportions.

RESULTS

Among 101 subjects, more subjects preferred a horizontal over a vertical format (48 vs. 37, P = 0.23; 16 no preference), and intermediate length over long/short instructions (44 vs. 14 vs. 31, P = 0.004; 12 no preference). A scale range of 0-10 was preferred over 0-100 (62 vs. 21, P < 0.001; 18 no preference). A bar indicator was preferred over a column for computerized touchscreen VAS (54 vs. 44, P = 0.31; 3 no preference). Only presence of chronic medical conditions influenced subject preference [odds ratio (95% confidence interval): 3.9 (1.6-9.6), P = 0.002].

CONCLUSION

Chinese-speaking subjects preferred a 0-10-point VAS with intermediate length instructions for HRQoL assessment. Thus, a 0-10-point VAS with intermediate length instructions may be more useful for HRQoL assessment among Chinese subjects.

Measurement of pain

Pain is a personal, subjective experience influenced by cultural learning, the meaning of the situation, attention, and other psychologic variables. Approaches to the measurement of pain include verbal and numeric self-rating scales, behavioral observation scales, and physiologic responses. The complex nature of the experience of pain suggests that measurements from these domains may not always show high concordance. Because pain is subjective, patients' self-reports provide the most valid measure of the experience. The VAS and the MPQ are probably the most frequently used self-rating instruments for the measurement of pain in clinical and research settings. The MPQ is designed to assess the multidimensional nature of pain experience and has been demonstrated to be a reliable, valid, and consistent measurement tool. A short-form MPQ is available for use in specific research settings when the time to obtain information from patients is limited and when more information than simply the intensity of pain is desired. The DDS was developed using sophisticated psychophysical techniques and was designed to measure separately the sensory and unpleasantness dimensions of pain. It has been shown to be a valid and reliable measurement of pain with ratio-scaling properties and has recently been used in a clinical setting. Behavioral approaches to the measurement of pain also provide valuable data. Further development and refinement of pain measurement techniques will lead to increasingly accurate tools with greater predictive powers.

The role of psychological factors in chronic pain. II. A critical appraisal

This paper, the second of two, concerning the study of psychological factors in chronic pain, presents a critical appraisal of the literature. Questionable assumptions, flawed methodology, and conceptual problems in earlier work are discussed, as are gradual improvements in methodological rigour and conceptual clarity. Methodological weaknesses in studies, including lack of control groups, selection biases, overinterpretation of correlational data, and use of inappropriate testing instruments are examined. Questions are raised about persisting tendencies to split mind from body by attributing pain to either organic or psychological causes. Despite advances in research and thinking in recent years, several issues remain unresolved in both the research enterprise and the clinical setting. These are discussed in relation to the respective needs of the researcher, the clinician, and the patient. Limitations on research conducted in clinical settings are considered and targets for improved methodology in studies are identified.