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Methodological shortcomings in prognostic modeling for patients with spinal disorders are highly common. This general commentary discusses methodological challenges related to the specific nature of this field. Five specific methodological challenges in prognostic modeling for patients with spinal disorders are presented with their potential solutions, as related to the choice of study participants, purpose of studies, limitations in measurements of outcomes and predictors, complexity of recovery predictions, and confusion of prognosis and treatment response. Large studies specifically designed for prognostic model research are needed, using standard baseline measurement sets, clearly describing participants’ recruitment and accounting and correcting for measurement limitations.

Objectives: The aim of this study was to reanalyze and reinterpret data obtained in Paracetamol in Acute Low Back Pain (PACE), the first large randomized controlled trial evaluating the efficacy of paracetamol in acute low back pain, to assess the inferential reproducibility of the original conclusions. Study Design and Setting: Mixed effects models were used to reanalyze pain intensity (primary outcome; 11-point Numeric Rating Scale) and physical functioning, health-related quality of life, sleep quality, and time until recovery (as secondary outcomes), according to the intention-to-treat principle. The original authors of the PACE study were not involved in the development of the methods for this reanalysis. Results: The reproduction analyses indicated no effect of treatment on pain intensity and confidence intervals excluded clinically worthwhile effects (adjusted main effect for regular paracetamol vs. placebo 0.00 [−0.02, 0.01; P = 0.85]; adjusted main effect for paracetamol as-needed vs. placebo 0.00 [−0.02, 0.01; P = 0.92]). Similar results were obtained for all secondary outcomes. Conclusion: This study indicates that the conclusions of the PACE trial are inferentially reproducible, even when using a different analytical approach. This reinforces the notion that the management of acute low back pain should focus on providing patients advice and reassurance without the addition of paracetamol.

Objective To synthesize the measurement properties of six health-related quality of life instruments (Short Form 36 [SF-36], Short Form 12 [SF-12], EuroQol 5D-3L [EQ-5D-3L], EuroQol 5D-5L [EQ-5D-5L], Nottingham Health Profile (NHP), and Patient-Reported Outcome Measurement Information System Global Health [PROMIS-GH-10]) in patients with low back pain (LBP). Study Design and Setting Six electronic databases (MEDLINE, EMBASE, CINAHL, PsycINFO, SportDiscus, and Google Scholar) were searched (July 2017). Studies assessing any measurement property in nonspecific LBP patients were included. Two reviewers independently screened the articles and assessed the risk of bias (COSMIN checklist). Consensus-based criteria were used to rate measurement properties results as sufficient, insufficient, or inconsistent; a modified GRADE approach was adopted for evidence synthesis. Results High quality evidence was found for insufficient construct validity of SF-36 summary scores, and EQ-5D-3L utility and visual analogue scale scores. Moderate evidence was found for sufficient construct validity of SF-12 physical summary score and inconsistent responsiveness of EQ-5D-3L utility score. Very low quality evidence was found on each instrument's content validity; very low to low evidence underpinned the other assessed measurement properties. EQ-5D-5L, NHP and PROMIS Global Health-10 were not evaluated in LBP patients. Conclusion Documentation of the measurement properties of health-related quality of life instruments in LBP is incomplete. Future clinimetric studies should prioritize content validity.