In search of a better way to assess itch

May 22, 2020

Researchers evaluating several itch assessment tools say there is a need for a better way. Studies comparing the validity and reliability of itch measurement scales are lacking, say researchers who examined several available assessment tools.

Researchers evaluating several available itch assessment tools found that while the Itch Severity Scale (ISS) demonstrated good retest reliability and high correlation with the pruritis-specific quality of life instrument ItchyQoL, the Itch Severity Scale isn’t ideal for practice. It’s too time-consuming for routine clinical use.
So, the researchers concluded dermatologists and others who assess patients in practice need an easier-to-perform alternative itch measurement scale. The alternative test, possibly a simplified Itch Severity Scale, needs to be highly reproducible and accurate in the way it reflects patients’ quality of life, according to the paper published January 2020 in the Journal of the American Academy of Dermatology (JAAD).1
While there are many tools for evaluating patients’ itch, there is no gold standard pruritus evaluation tool for dermatologists and other providers to use in practice. Optimal tools are also needed in research, according to the authors.
“Studies evaluating pruritus have tended to focus on the pathogenesis and effective treatment and often overlook the measurement of symptoms,” they wrote. “However, the investigation of validated and reliable itch intensity scales may provide a more accurate representation of pruritus and play a useful role as a benchmark for research and clinical practice.”
Studies comparing the validity and reliability of itch measurement scales are lacking, according to the paper.
Researchers studied 419 patients with chronic itch at 11 Korean hospitals. They evaluated use of the Visual Analog Scale (VAS), Numeric Rating Scale (NRS), Verbal Rating Scale (VRS) and the multidimensional Itch Severity Scale questionnaire. They also assessed these tools’ correlations with the ItchyQoL.
The Visual Analog Scale is a horizontal image with “no itch” on the far left and “worst imaginable itch” on the far right. Patients mark a place on the 10-cm scale indicating the severity of their itch. The Numeric Rating Scale allows patients to assign a numeric score to their itch, from 0, or no itch, to 10, which is the worst possible itch. Patients using the Verbal Rating Scale score itch intensities as 0 to 4, with 0 being no itch and 4 indicating very severe itch. The International Forum for the Study of Itch studied these three scales and reported high reliability and validity, according to the paper.
The seven-category Itch Severity Scale addresses itch frequency, itch description, body surface area impacted and itch intensity according to one’s state of itching (best, average or worst). It also addresses how one’s itch affects mood, sexual desire and function, as well as sleep.
Subjects in the JAAD paper recorded itch intensity using the four scales. Researchers then analyzed retest reliability 3 hours after the first assessment. All subjects answered the ItchyQoL, which includes 22 pruritus-specific questions about symptoms, functional limitations and emotions. Patients score their responses from 1, or never, to 5, or always.
Researchers found a significantly strong correlation among the Visual Analog Scale, Numeric Rating  Scale and Verbal Rating Scale. The Itch Severity Scale, a multidimensional scale, showed a low intercorrelation validity with these three scales but demonstrated a notably better retest reliability and stronger ItchyQoL correlation than the three unidimensional tools.
The Itch Severity Scale, while it performed well in the study, isn’t easy to use in a busy practice, according to the paper. What providers need is a less time consuming, reliable itch assessment tool that they can use routinely in practice-one that overcomes the challenge of accurately measuring patients’ complex and subjective feelings of itch.
Patient heterogeneity and recall bias are study limitations.

Disclosures:

The authors report no conflicts of interest

References:

1 Jang YH, Kim SM, Eun DH, Park KD, Park GH, Kim BS, Li K, Park CO, Kim HO, Kim HS, Jang MS, Doh EJ, Lee DH, Lee YW, Kim DW, Kim SJ. Validity and reliability of itch assessment scales for chronic pruritus in adults: A prospective multicenter study. J Am Acad Dermatol. 2020 Jan;82(1):80-86.