|Study title: The predictive ability of the STarT Back Tool was limited in people with chronic low back pain: a prospective cohort study
Authors: Kendell M, Beales D, O’Sullivan P et al.
Publication Information: Journal of Physiotherapy 2018; 64: 107-113.
Chronic low back pain (LBP) is the leading cause of disability worldwide, and carries a tremendous economic burden. Evidence-based guidelines have recommended screening for poor prognostic indicators and stratifying LBP patients based on chronicity and disability risk. The STarT Back Tool (SBT) was created to enable primary care/first contact practitioners to dictate future LBP care pathways, based on the risk of future disability. A randomized trial demonstrated that a risk stratification approach based on the SBT resulted in better clinical outcomes and reduced costs compared to usual care in UK primary care consults. Since, multiple studies have been conducted supporting the psychometric properties, and the predictive and discriminative ability of the SBT. However, the SBT risk subgroups have not been profiled, nor have the tool’s predictive and discriminative ability been adequately investigated in a chronic LBP population. As such, the authors sought to determine the predictive and discriminative validity of the SBT for pain intensity, self-reported LBP-disability and self-perceived change at 1-year follow-up. They also hoped to determine the profile of the SBT chronic LBP risk subgroups with respect to demographic variables, pain intensity, self-reported disability and psychological measures.
Follow-up data were available for 264 patients (91 per cent of the original sample of 290). No significant difference was found for age, gender or baseline pain intensity for responders and non-responders. Non-responders had higher baseline disability and risk status than responders. The SBT categorized 82 participants (28 per cent) as low risk, 116 (40 per cent) as high moderate risk and 92 (32 per cent) as high risk. The SBT risk subgroups did not differ significantly for most of the demographic variables, including pain duration. However, pain intensity and disability, increased stepwise from the low-risk group to the high-risk group. Also, consistently greater negative psychosocial affect and cognition, decreasing self-efficacy and chronic pain acceptance were also seen from the low-risk group through to the high-risk group.
Patients in the medium-risk and high-risk groups had a 25 per cent increased risk of not recovering with respect to pain compared to the low-risk group. Participants in the medium-risk group had a 130 per cent increased risk, and those in the high-risk group had a 186 per cent increased risk of not recovering with respect to disability, when compared to the low-risk group. However, although a higher proportion of both the medium and high-risk groups perceived themselves as not improved compared to the low-risk group, the difference in risk was not statistically-significant.
Interestingly, the positive likelihood ratios were higher and the negative likelihood ratios were lower for disability compared to pain. The sensitivity analysis using the follow-up measures showed that the SBT was significantly and most strongly predictive of disability (r2 = 0.09), significantly but less predictive of pain (r2 = 0.04) and not predictive of global perceived change (r2 = 0.00).
The SBT was initially designed to risk-stratify patients with non-specific LBP into various chronicity and disability profiles and outcomes, with a matched care pathway for each subgroup. It has been shown to be predictive and discriminative of future disability due to LBP in primary care.
In this study, those in the higher SBT risk categories had significantly greater pain intensity and disability, higher scores on negative psychosocial outcomes, and lower scores on positive psychosocial constructs at baseline. This is consistent with past studies which have demonstrated that SBT risk subgroups are related to pain, disability, depression, fear avoidance beliefs, catastrophizing, kinesiophobia and anxiety. These results indicate that the SBT may be an acceptable surrogate measure for multiple full-length unidimensional measures. However, the SBT performed poorly with respect to pain intensity and subjective global perceived change at the 1-year follow-up. Therefore, using the SBT as a sole indicator of prognosis in chronic LBP is NOT recommended. However, the SBT should be used alongside the clinical examination and in conjunction with sound clinical reasoning when making care decisions for chronic LBP patients.
Dr. Shawn Thistle is a practicing chiropractor, educator, international speaker, knowledge-transfer leader, evidence-based health care advocate, entrepreneur & medicolegal consultant. He founded RRS Education in 2006 and currently acts as the company's CEO. RRS Education helps chiropractors and other manual medicine clinicians around the world integrate research in to patient care via weekly Research Reviews, Online Courses and Seminars. For more information, visit: www.rrseducation.com.