Response rate does not affect patient-reported outcome after lumbar discectomy.

Purpose: Quality registers give unique possibilities to achieve information from large groups of patients, but outcome must be interpreted carefully due to less stringent data collection and lower follow-up rates than in research projects. We tried to quantify any outcome differences between a national spine quality register and a prospective observational study.

Methods: Adult patients treated with lumbar discectomy between 2004 and 2010 were retrieved from the Swedish Spine register (Swespine) (n = 7791) and from the single center lumbar disc herniation study (LDHS) in Stockholm (n = 177). The mean follow-up rates at 1 and 2 years were 73 and 62%, compared to 98 and 99%, respectively. Patient-reported outcome measurements included VAS for back and leg pain, ODI, EQ-5D, patient satisfaction, and global assessment.

Results: When comparing the two cohorts at baseline, there were minor differences in the patient-reported outcome measurements, all within reported minimal clinical important differences (MCID). Mean outcome improved significantly in both groups after surgery. All outcomes at 1 and 2 years were similar and within the reported MCID in both groups. Complications and reoperations were similar, except for more surgical site infections in the LDHS group.

Conclusions: Higher response rates than seen in Swespine are not needed to achieve reasonably representative data on patient-reported outcome for large cohorts. Two-year data do not seem to add additional information. These slides can be retrieved under Electronic Supplementary Material.