Criterion validation of the rate of recovery, single alphanumeric measure, in patients with low back pain.
BACKGROUND AND PURPOSE
The aim of this study was to determine the criterion validity of patient rate of recovery with the Oswestry Disability Index (ODI) and the Numeric Pain Rating Scale (NPRS).


METHODS
Associations between rate of recovery and ODI and pain were examined using a receiver operating characteristic (ROC) curve. Participants were dichotomized to ODI 50% change versus a <50% change. Pearson correlation coefficients were performed to determine the relationship between the continuous variables of rate of recovery and final ODI score at discharge. Spearman correlation coefficients were performed to determine the relationship between the continuous variable rate of recovery and ordinal variable final pain score at discharge.


RESULTS
ROC curve statistics suggest that a cut-point of greater than 82.5% on the self-report rate of recovery (sensitivity = 0.72, specificity = 0.71 and positive likelihood ratio = 2.44) corresponded to a 50% change on the ODI. The correlation between ODI final score and self-report rate of recovery was a moderate, -0.45 (p < 0.01). Cut-points on the self-reported rate of recovery ranged from 72.5% to 82.5% depending upon the definition of change in pain (≥2, ≥3 and ≥4 points) score or final pain score (<5/10, <4/10 and <3/10). The correlation between NPRS final score and self-report rate of recovery was -0.72 (p < 0.01). The correlation between NPRS change score and self-report rate of recovery was 0.42 (p < 0.01).


DISCUSSION
Patients reporting greater than or equal to 82.5% on rate of recovery are likely to have met a 50% change on the ODI. The moderate correlation between rate of recovery and ODI suggests that rate of recovery may capture a dimension of recovery in addition to the self-reported function in patients with low back pain. Both outcomes measures can be used to capture a more comprehensive evaluation of recovery from low back pain.