Assessment properties of the Visual Analogue scale, Numeric Rating Scale, Face Pain Scale, and Pain Intensity...

Pain intensity is the primary variable assessed in clinical trials for low back pain. A precise assessment of pain intensity is vital for the informed selection of medical and rehabilitation treatments; it represents a notable challenge in clinical settings.

The four pain intensity scales - Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), Faces Pain Scale (FPS), and Brief Pain Inventory (BPI-IS) - were administered to 200 Albanian participants with low back pain at a regional healthcare center in Albania with a mean age of 69.77 and a standard deviation (SD) of 6.34. The mean of pain duration was 3.51 with a SD of 0.72. Participants were subsequently asked to assess four domains of pain intensity - worst pain, average pain, least pain over the past week, and current pain. The data collection occurred during the patients' initial visits for low back complaints. To assess the convergent validity of the scales - specifically, the relationship between each scale and a composite score of all measures, a principal components analysis was performed.

There were significant correlations among the four scales across all domains of pain intensity in the 200 participants. The screen test from the principal component analyses indicated that the four scales captured a single overarching domain for each of the four pain intensity areas, with the first eigenvalue ranging from 2.33 to 3.63 and the second from 0.16 to 0.43. Moreover, all the scales showed a strong loading on the single component that emerged. The four scales had the highest loading on 'current pain' component (>0.9).

The VAS, NRS, FPS and BPI-IS are valid and can be used for the clinical and research implication in the Albanian population.

The study was registered at clinical trial.gov before the data collection with ID. NCT04131998.