BACKGROUND AND PURPOSE Loss to follow-up in observational studies may skew results and hamper study reliability. We evaluated the importance of loss to follow-up in the Swedish spine register. PATIENTS Patients operated in the lumbar spine and scheduled for a postal questionnaire follow-up during part of 2016 were identified. Out of the 351 patients, 203 had responded. After multiple attempts, 115 of the 148 non-responders were reached; 68 returned the complete questionnaire; and 47 answered a brief questionnaire by phone. Analyses were made with the Chi-square test, analysis of covariance or logistic regression. Some analyses were adjusted. RESULTS At baseline, the non-responders were younger than the responders (55 vs 61 years, p < 0.001) and had higher Oswestry Disability Index (ODI) (54 vs 48, p = 0.003), lower SF-36 physical component summary score (PCS) (36 vs 40, p = 0.011) and lower EQ-5D (0.17 vs 0.27, p = 0.018). Mean back pain, leg pain, ODI, EQ-5D, SF-36 mental component summary score (MCS) improved significantly in both groups (all p < 0.001). SF-36 PCS did not improve in the non-responder group (p = 0.063). Non-responders perceived less improvement in back pain (global assessment back 60% vs 72%, p = 0.002). At follow-up, there were no differences in patient-reported outcome measures between the groups (all p ≥ 0.06), with the exception of a lower SF-36 MCS among the non-responders (p = 0.015). INTERPRETATION After surgery for lumbar spine degenerative disorders, non-responders achieve similar outcome as responders in the Swedish spine register, with the exception of a lower mental health and less perceived improvement in back pain. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

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瑞典脊柱注册中对随访结果解释的损失很小。

背景和目的观察性研究的后续研究可能会失去结果，并影响研究的可靠性。我们评估了损失对瑞典脊柱骨科随访的重要性。患者已确定在2016年部分时间接受腰椎手术并计划接受邮政问卷调查的患者。在351例患者中，有203例有反应。经过多次尝试，在148个无响应者中达到了115个。68份返回完整问卷；47人通过电话回答了一份简短的问卷。用卡方检验，协方差分析或逻辑回归进行分析。一些分析进行了调整。结果在基线时，无反应者比反应者年轻（55岁对61岁，p <0.001），并且Oswestry残疾指数（ODI）更高（54对48，p = 0.003），较低的SF-36物理成分汇总评分（PCS）（36 vs 40，p = 0.011）和较低的EQ-5D（0.17 vs 0.27，p = 0.018）。两组的平均背痛，腿痛，ODI，EQ-5D，SF-36精神成分综合评分（MCS）均有显着改善（所有p <0.001）。SF-36 PCS在无反应组中未改善（p = 0.063）。无反应者认为背部疼痛的改善较小（总体评估，背部疼痛改善60％vs 72％，p = 0.002）。随访时，两组之间患者报告的结局指标无差异（所有p≥0.06），无应答者中SF-36 MCS较低（p = 0.015）。解释腰椎退行性疾病手术后，无反应者的疗效与瑞典脊柱病史中的反应者相似，但精神健康水平较低，并且背痛的改善较少。