Do three-month spine surgery outcomes predict results at twelve months?

Registry platforms lie at the center of all emerging evidence-driven reform models and will be used to inform decision makers in health-care delivery. The researchers set out to determine whether three-month patient reported outcomes accurately predict 12-month outcomes, and hence, whether three-month measurement systems suffice to identify effective versus non-effective spine care.

All patients undergoing lumbar spine surgery for degenerative disease at a single institution over a two-year period were enrolled in a prospective longitudinal registry. Patient reported outcome instruments were recorded prospectively at baseline, three months and 12 months, postoperatively. Receiver operating characteristic (ROC) curve analysis performed to determine whether improvement in general health state (EQ-5D) and disability (ODI) at three months accurately predicted improvement and achievement of minimum clinical important difference (MCID) at 12 months.

The study included 593 patients. There was correlation between three- and 12-month EQ-5D (r=0.71;p<0.0001) and ODI (r=0.70;p<0.0001); however, researchers observed sizable discrepancy in achievement of a clinically significant improvement (MCID) threshold at three versus 12 months on the individual patient level. For postoperative disability (ODI), 11.5 percent of patients that achieved MCID threshold at three months dropped below threshold at 12 months; and, 10.5 percent of patients who did not meet MCID threshold at three months surpassed MCID threshold at 12 months. For ODI, achieving MCID at three months accurately predicted 12 month MCID with only 62.6-percent specificity and 86.8- percent sensitivity.

For postoperative health utility (EQ-5D), 8.5 percent of patients lost MCID threshold improvement from three to 12 months, while 4.0 percent gained MCID threshold between three and 12 months postoperatively. For EQ-5D (quality adjusted life years), achieving MCID at three months accurately predicted 12 month MCID with only 87.7-percent specificity and 87.2-percent sensitivity.

Patient-reported measures of treatment effectiveness obtained at three months correlated with 12 month measures overall in aggregate, but did not reliably predict 12-month outcome at the patient-level. Prospective longitudinal spine outcomes registries need to span at least 12 months to identify effective versus non-effective patient care.