Chronic low back pain clinical outcomes present higher associations with the STarT Back Screening Tool than with physiologic measures: a 12-month cohort study

Abstract

Background: Stratification strategies based on identifying patient's prognosis in order to guide patient care constitute one of the most prominent and recent approach in low back pain research. The STarT Back Screening Tool (SBST) although promising, has not been studied in patients with chronic low back pain (cLBP). Considering how challenging it is to translate research into practice, the value of integrating a new tool should be thoroughly assessed. The purpose was therefore to assess associations between the short- and long-terms clinical status and two types of variables, physiologic measures and the SBST, in participants with cLBP. The ability of both types of variables to discriminate between participants with and without higher levels of disability, pain, fear of movement and patient's global impression of change was also investigated.

Methods: Fifty-three volunteers with cLBP participated in an initial evaluation and follow-ups at 2-, 4-, 6- and 12-month. Physiologic measures (maximal voluntary contraction, maximal endurance and muscle activity evaluated during prone and lateral isometric tasks) and the SBST were assessed at baseline. Disability (Oswestry Disability Index, ODI), pain intensity (101-point Numerical Rating Scale, NRS), fear of movement (Tampa Scale for Kinesiophobia, TSK) and patient's global impression of change (7-point scale, PGIC) were evaluated at baseline and at each follow-up. Aside the use of correlation analyses to assess potential associations; ROC curves were performed to evaluate the discriminative ability of physiologic measures and the SBST.

Results: The SBST allowed for the identification of participants presenting higher levels of disability (ODI ≥24 %), pain (NRS ≥37 %) or fear of movement (TSK ≥41/68) over a 12-month period (AUC = 0.71 to 0.84, ps < 0.05). The SBST score was also correlated with disability at each follow-up (τ = 0.22 to 0.33, ps < 0.05) and with pain intensity and fear of movement at follow-ups. Among physiologic measures, only maximal voluntary contraction was correlated to disability, pain intensity or fear of movement during the follow-up (|τ| = 0.26 to 0.32, ps < 0.05) and none was able to identify participants presenting higher levels of outcomes (AUC ps > 0.05).

Conclusion: Physiologic measures obtained during prone and lateral tests have limited associations with the clinical status over a 12-month period in patients with nonspecific chronic low back pain. On the other hand, the STarT Back Screening Tool is useful for the identification of patients who will present higher levels of disability, pain intensity and fear of movement over a year.

Trial registration: Clinicaltrials.gov NCT02226692.

Figures

Fig. 1

a. Prone position and b. Right lateral position. These positions were used to assess the endurance and the MVC of trunk muscles

Fig. 2

Matrices used in the recording of lumbar muscles activity during prone position tasks

Fig. 3

Flow of participants through the study. Within parenthesis are the percentages of total participants at baseline (T0). Within brackets are the means (± SD) of number of days for completion

Fig. 4

ROC curves at 6- (full line) and 12- (dashed line) month for the SBST against outcome variables. Area under curve (AUC) are reported with 95 % CI in regard of a. Disability, b. Pain intensity and c. Fear of mbovement. * p < 0.05 and ** p ≤ 0.01

Fig. 5

Sensitivity and specificity for STarT Back Screening Tool (SBST) cut-offs. Sensitivity and specificity in the identification of participants presenting higher levels of disability (a), fear of movement (b), and pain (c) at 6- (T3) and 12-month (T4) follow-ups