By Erik MacLaren, PhD
Pain-intensity reductions calculated from pre- and post-treatment assessments are only modestly correlated with patient-reported pain reductions, according to results of a retrospective analysis presented here at the 35th Annual Meeting of the American Academy of Pain Medicine (AAPM).
The analgaesic effectiveness of a treatment can be determined by 2 methods. First, a calculated percentage of pain reduction (CPPR) can be determined using the change between pre- and post-treatment pain scores on the Numerical Rating Scale (NRS) or the Visual Analogue Scale (VAS). Alternatively, patient-reported percentage pain reduction (PRPPR) can be used to assess treatment-related changes in pain.
N. Nick Knezevic, MD, PhD, Advocate Illinois Masonic Medical Center, Chicago, Illinois, and colleagues assessed the correlation between CPPR and PRPPR using the records of 803 patients from their institution who were treated for chronic pain and followed for at least 1 year.
The average length of follow-up was 30 ± 11.7 months, and all patients in the sample had a significant pain reduction, calculated using NRS scores (P< .001).
The investigators found that the mean NRS decreased from 8.1 ± 1.4 pre-treatment to 4.1 ± 1.9 post-treatment, and the resulting mean CPPR was 49.8 ± 21. The mean PRPPR was 62 ± 20.9.
Using both the intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC), and noting that the CPPR and PRPPR diverged by more than 30% in nearly half the sample population, the researchers determined that the correlation between the 2 measures was only moderate.
These results indicate a need for a multi-dimensional, periodic pain assessment for treatment effectiveness that includes components to educate patients and assess the expectations they have around their pain, Dr. Knezevic suggested.
The patient population in this study was predominantly female (60.1%), with a high preponderance of low back pain (69.6%); the average age was 60.1 ± 14.4 years.