Development of a metric for a day of manageable pain control: derivation of pain severity cut-points for low back pain and osteoarthritis

The objective of this study was to adapt the concept of 'episode-free day', a metric for measuring symptom relief in daily units, to the clinical outcome literature for persistent pain. The episode-free day metric is widely used in other medical literature, but no analogous measure exists in pain literature. Prior focus groups with this population suggested that a 'Day of Manageable Pain Control' was an appropriate name for the metric. In the present study, in order to derive a statistical criterion for 'Manageable Day', we used Serlin et al.'s (Pain 61 (1995) 277) cut-point derivation method to derive a single cut-point on a 0-10 scale of average pain that divided groups with significant persistent pain optimally on pain-related functional interference. Participants were 194 patients with moderate-severe low back pain (n=96) or osteoarthritis (n=98). For both patient samples, '5' was the cut-point that optimally distinguished groups on pain-related interference. '5-8' and '5-7' were double cut-point solutions that optimally divided LBP and OA samples into three categories (e.g. lowest, medium and highest average pain), respectively. Derived cut-points were confirmed using a variety of measures of functional disability. Together with research that showed that average pain ratings of approximately 5 and below permit increased function and quality of life in patients with moderate to severe low back pain and osteoarthritis, our findings provide support for the use of 0-5 on a 0-10 numeric average pain severity scale as one possible criterion for a Manageable Day.