Comments on ‘Assessment properties of the Visual Analogue Scale, Numeric Rating Scale, face pain Scale, and pain intensity subscale of the Brief Pain Inventory in Albanian population with low back pain’

Dear Editor

We read with interest the cross-sectional study by Todri and colleagues on pain intensity assessment in Albanian adults with low back pain [1]. In 200 patients (mean age 69.77 years), the authors administered the Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), Faces Pain Scale (FPS), and the pain intensity subscale of the Brief Pain Inventory (BPI-IS) to capture current, least, average, and worst pain over the previous week. The four instruments were highly correlated, and principal components analyses supported a dominant factor per domain, with very high loadings for current pain. VAS was most preferred (36%), followed by NRS (29%), FPS (22.5%), and the fourth measure (12.5%; labelled as ‘BRS’ in the Results) [1]. These findings provide an important foundation for pain measurement in Albania.

From a measurement perspective, it would be helpful to distinguish more clearly between convergent validity and clinical interchangeability. Strong correlations and a single-factor structure indicate that the scales tap a common construct, but they do not show that scores can be substituted at the level of individual patients. Agreement-oriented analyses, such as Bland-Altman plots with limits of agreement and estimates of measurement error, would clarify whether VAS, NRS, FPS, and BPI-IS can be used interchangeably [2]. Additional properties—test–retest reliability in clinically stable patients, responsiveness to change, and interpretability indices such as floor/ceiling effects and minimal detectable change—would further support or refine the conclusion that all four scales are valid in this population [3].

Generalisability of the results also warrants cautious interpretation. Recruitment from a single centre, an older sample, and heterogeneous diagnoses (nonspecific low back pain, arthritis, fractures, and trauma) may limit broader applicability [1]. Stratified analyses or models adjusting for diagnosis, education, and comorbidity could explore whether psychometric performance is consistent across subgroups with different pain mechanisms and cognitive profiles. For transparency, we also suggest harmonising the reporting of correlation coefficients (Spearman’s versus Pearson) and consistently labelling the BPI-IS across text and tables.

The adapted FPS, expanded from nine to eleven faces and modified by removing tears, raises additional issues of cultural and content validity [1]. Such changes may alter category meaning and shift the latent trait underlying responses. Brief cognitive interviews in Albanian—asking patients what each face represents and how they choose between adjacent faces—would provide evidence that the revised FPS functions as intended. Qualitative exploration could also clarify why VAS was preferred despite its visual and cognitive demands in an elderly cohort, and whether preference aligns with actual usability.

In summary, Todri et al. [1] provide valuable preliminary evidence on pain intensity scales in Albanian patients with low back pain and show that VAS, NRS, FPS, and BPI-IS are feasible in this context. Further evaluation of agreement, reliability, responsiveness, and qualitative aspects would strengthen their psychometric basis and clinical applicability. A pragmatic pathway using NRS by default, VAS for finer discrimination, FPS for communication barriers, and BPI-IS for weekly assessment may balance methodological rigour with patient-centred pain care in Albania.

Ethical statement

Not applicable.

Disclosure statement

The authors declare no competing interests.

Data availability statement

No data were generated or analyzed in this study.