[Pain assessment in invasive diagnostic procedures. Comparison of an eleven-point numerical rating scale and a six-point verbal rating scale for pain measurement in bone marrow puncture]

Abstract

Background and objective: Pain measurement during diagnostic procedures is an accepted prerequisite for appropriate therapy. In this study, the agreement between rankings of pain intensity on a numerical and a verbal rating scale was analyzed.

Methods: Patients attending a haematological outpatient clinic who underwent bone marrow puncture were requested to assess pain intensity perceived during the procedure on a elen-point numerical and a six-point verbal rating scale.

Results: Analysis of patients' pain ratings in 263 bone marrow punctures showed a very good correlation between numerical and verbal rating scale (Spearman correlation coefficient 0,86). By means of a transfer instruction categories of the verbal rating scale were assigned to figures of the numerical rating scale (0 - no pain, 1 or 2 - mild p., 3, 4 or 5 moderate p., 6 or 7 severe p., 8, 9 or 10 - very severe and worst possible pain). The resulting transfer table showed a good agreement with a weighted kappa of 0.72 (95% confidence interval: 0.66-0.79).

Conclusion: Both scales can be employed efficiently for pain assessment during diagnostic procedures. Verbal categories can be assigned to numerical values and vice versa numerical values to verbal categories. However, in view of the inter-individual variations it appears appropriate to re-assure pain perception with each patient in order to avoid over- or undertreatment.