Acute low back pain and primary care: how to define recovery and chronification?

A prospective cohort study.

To establish outcome measures for recovery and chronic pain for studies with patients who present with recent-onset acute low back pain (LBP) in primary care.

Among back pain researchers, no consensus exists about outcome definitions or how to identify primary-care patients as not-recovered from an episode of LBP. Cut points for outcome scales have mostly been arbitrarily chosen. Theoretical models for establishing minimal important change values in studies of patients with LBP have been proposed and need to be applied to real data.

A sample of 521 patients who presented with acute LBP (<4 weeks) in primary care clinics were observed for 6 months and scores for pain and disability were compared with ratings on a Global Perceived Effect Scale. Using multiple potential "gold standards" as anchors (reference standards), the receiver operating characteristic method was used to determine optimal cut points for different ways of defining nonrecovery from acute LBP.

Minimal important change values and upper limits for pain and disability scores as well as minimal important percentage changes are presented for five different definitions of recovery. A previously suggested 30% change from baseline scores does not accurately discriminate between recovered patients and nonrecovered patients in patients presenting with acute LBP in primary care.

Outcome definitions that combine ratings from perceived recovery scales with pain and disability measures provide the highest accuracy in discriminating recovered patients from nonrecovered patients.