Patients remember their initial pain as worse than they rated it at the time, when surveyed months after undergoing spinal surgery for back pain reports a study in the Feb. 1 issue of the journal Spine.
Studies relying on such after-the-fact ratings may overestimate the effectiveness of spinal surgery in relieving chronic back pain, concludes a research team led by Ferran Pellisé, MD, of Hospital Vall d'Hebron, Barcelona, Spain.
The researchers studied before-and-after ratings made by 58 patients who underwent lumbar fusion surgery for chronic low back pain. Before their operation, all patients completed standard evaluations of back pain and related disability. These prospective ("forward-looking") ratings were compared with retrospective ("backward-looking") ratings made an average of three years after surgery.
When recalling their preoperative state, patients consistently rated themselves worse than in their original questionnaires. For example, on a simple 10-point scale, the patients' original average pain rating was 7.0. On follow-up ratings, the patients recalled their pain as being significantly worse: average rating 8.2. Based on the original ratings, surgery produced an average pain reduction of 3.3 points on the 10-point scale.
In contrast, if the recalled ratings were used, the average improvement would have been 4.6 points. Similar patterns were noted for other standard ratings of back pain and related disability. The extent of recall bias did not differ significantly for patients with shorter versus longer times since surgery. The ratings did not vary in any systematic way, so there was no way to adjust for them statistically.
Retrospective studies -- in which patients are asked to remember and rate their state of health before treatment -- are widely used in medical research. However, few previous studies have looked at how patients' recollections measure up to actual pretreatment ratings. The use of retrospective studies to assess the results of spinal surgery has increased in recent years. Relying on such after-the-fact pain ratings may give the impression that surgery for back pain is more effective than it actually is, the new results suggest.
Pellisé and colleagues conclude, "Our study shows that relying on a patient's recall of his or her preoperative status a few months or years after surgery is not a valid method for establishing baseline status when treating low back pain."
Source: Lippincott Williams and Wilkins
