Patient-reported three-month spine surgery outcomes do not reliably predict results at twelve months

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Matthew J McGirt presented research on the accuracy of patient-reported outcomes at three-months in predicting 12-month outcomes after spine surgery during the 2015 American Association of Neurological Surgeons (AANS) Annual Scientific Meeting (AANS; 2–5 May, Washington, DC, USA).

McGirt said that registry platforms lie at the centre 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 (Oswestry Disability Index—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% of patients that achieved MCID threshold at three months dropped below threshold at 12 months; and 10.5% 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% specificity and 86.8% sensitivity.

For postoperative health utility (EQ-5D), 8.5% of patients lost MCID threshold improvement from three to 12 months, while 4% 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% specificity and 87.2% 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 outcomes at the patient-level. Prospective longitudinal spine outcomes registries need to span at least 12 months to identify effective versus non-effective patient care.

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