The Clinical Course of Low Back Pain
The Clinical Course of Low Back Pain
Included were studies (RCTs and prospective observational cohort studies) conducted for primary care treatment for LBP (e.g. analgesia, exercises, manipulation therapy) among individuals aged 18 or over. Studies had to provide baseline and follow-up data on the designated primary outcome measure of pain intensity, measured on a Numerical Rating Scale (NRS) or Visual Analogue Scale (VAS). Only studies published in English were included. Also excluded were studies conducted among patients with specific LBP (e.g. cancer or inflammatory arthritis), post-operative or post-traumatic back pain, or back pain associated with pregnancy or labour.
To meet the specific aims of the study, the literature search did not have to be exhaustive, but to provide sufficiently large pool of studies. The Cochrane Central Register of Controlled Trials (CENTRAL) was therefore chosen as a sufficient data source for RCTs.. This search was an update (up to April 2012) of a strategy previously used and described elsewhere. For observational studies, a literature search was conducted for the same time period using the databases of AMED, EMBASE, MEDLINE and CINAHL based on the keywords 'low back pain', 'back pain', 'spinal pain', 'primary care', 'general practice', 'population', 'cohort', 'observational', 'prognosis', predictor' and 'course'. The detailed search strategy is shown in Additional file 1. References accompanying relevant systematic reviews and included cohort studies were also hand-checked to identify additional eligible studies.
The literature search was conducted by MA and screening of citations/abstracts ad selection of RCTs and cohort studies applying the inclusion criteria was conducted by MA, DVdW & KPJ.
The extracted data included:
Firstly, RCTs as a single group were compared with observational studies. Secondly, RCTs were sub-grouped into efficacy and pragmatic trials, based on whether the trial included a placebo, sham or no treatment, with such trials being grouped as efficacy trials. RCTs that included comparator treatment of usual care or waiting list arms were classified as pragmatic trials. To compare studies groups that are similar with regard to the type of treatment, a separate analysis was conducted to compare cohort studies with RCT arms that received 'usual care'. Each RCT sub-group was compared separately with observational studies.
Pain intensity scores were converted to a zero to 100 scale (least to most severe) where necessary by multiplication. Meta-analysis using a random effects model was performed using STATA/IC 11 software to compute pooled mean pain intensity scores (and 95% confidence intervals) at baseline and follow up, separately for RCT treatment arms and for observational studies. Commonly used follow-up times of 6, 13, 27 and 52 weeks were selected for comparison. Data on other time points were considered to fall within the selected points if they were within a three-week range.
To compare the size of improvement in outcome scores in RCTs and observational studies, the standardized mean change (SMC) was calculated for each RCT treatment arm and observational study by subtracting the follow-up mean outcome score from the baseline mean score and dividing by the standard deviation (SD) of baseline scores. Pooled SMCs were calculated using random effects meta-analysis. SMCs over 0.8 were considered large, 0.5 – 0.8 moderate and less than 0.5 small. The 95% Confidence Intervals for SMCs were calculated using the formula described by Hozo et al.. The variance (squared standard deviation, σ2) of response size was calculated using the following formula:
Where: c (n-1) approximates 1 - [3/4(n-1) –1], ρ is the population correlation between baseline and follow-up scores which was estimated as 0.5, n is sample size and δ is the SMC. Heterogeneity of studies' estimates was assessed by computing I statistic, where zero indicates no variation between studies and 100% indicates that all variation is the result of variation between studies. Meta-regression analyses were conducted to test the significance of the difference in the size of SMCs between RCTs and observational studies at the selected follow up points.
Methods
Criteria for Inclusion
Included were studies (RCTs and prospective observational cohort studies) conducted for primary care treatment for LBP (e.g. analgesia, exercises, manipulation therapy) among individuals aged 18 or over. Studies had to provide baseline and follow-up data on the designated primary outcome measure of pain intensity, measured on a Numerical Rating Scale (NRS) or Visual Analogue Scale (VAS). Only studies published in English were included. Also excluded were studies conducted among patients with specific LBP (e.g. cancer or inflammatory arthritis), post-operative or post-traumatic back pain, or back pain associated with pregnancy or labour.
Searching and Selection of Studies
To meet the specific aims of the study, the literature search did not have to be exhaustive, but to provide sufficiently large pool of studies. The Cochrane Central Register of Controlled Trials (CENTRAL) was therefore chosen as a sufficient data source for RCTs.. This search was an update (up to April 2012) of a strategy previously used and described elsewhere. For observational studies, a literature search was conducted for the same time period using the databases of AMED, EMBASE, MEDLINE and CINAHL based on the keywords 'low back pain', 'back pain', 'spinal pain', 'primary care', 'general practice', 'population', 'cohort', 'observational', 'prognosis', predictor' and 'course'. The detailed search strategy is shown in Additional file 1. References accompanying relevant systematic reviews and included cohort studies were also hand-checked to identify additional eligible studies.
The literature search was conducted by MA and screening of citations/abstracts ad selection of RCTs and cohort studies applying the inclusion criteria was conducted by MA, DVdW & KPJ.
Data Extraction
The extracted data included:
Study characteristics (publication year, country of study, clinical setting, study design, sample size).
Participants' characteristics (mean age;% female; duration of symptoms).
Interventions: name, dose and provider.
Outcome: baseline and follow up mean scores (and baseline standard deviation (SD)) for pain intensity.
Analysis
Firstly, RCTs as a single group were compared with observational studies. Secondly, RCTs were sub-grouped into efficacy and pragmatic trials, based on whether the trial included a placebo, sham or no treatment, with such trials being grouped as efficacy trials. RCTs that included comparator treatment of usual care or waiting list arms were classified as pragmatic trials. To compare studies groups that are similar with regard to the type of treatment, a separate analysis was conducted to compare cohort studies with RCT arms that received 'usual care'. Each RCT sub-group was compared separately with observational studies.
Pain intensity scores were converted to a zero to 100 scale (least to most severe) where necessary by multiplication. Meta-analysis using a random effects model was performed using STATA/IC 11 software to compute pooled mean pain intensity scores (and 95% confidence intervals) at baseline and follow up, separately for RCT treatment arms and for observational studies. Commonly used follow-up times of 6, 13, 27 and 52 weeks were selected for comparison. Data on other time points were considered to fall within the selected points if they were within a three-week range.
To compare the size of improvement in outcome scores in RCTs and observational studies, the standardized mean change (SMC) was calculated for each RCT treatment arm and observational study by subtracting the follow-up mean outcome score from the baseline mean score and dividing by the standard deviation (SD) of baseline scores. Pooled SMCs were calculated using random effects meta-analysis. SMCs over 0.8 were considered large, 0.5 – 0.8 moderate and less than 0.5 small. The 95% Confidence Intervals for SMCs were calculated using the formula described by Hozo et al.. The variance (squared standard deviation, σ2) of response size was calculated using the following formula:
Where: c (n-1) approximates 1 - [3/4(n-1) –1], ρ is the population correlation between baseline and follow-up scores which was estimated as 0.5, n is sample size and δ is the SMC. Heterogeneity of studies' estimates was assessed by computing I statistic, where zero indicates no variation between studies and 100% indicates that all variation is the result of variation between studies. Meta-regression analyses were conducted to test the significance of the difference in the size of SMCs between RCTs and observational studies at the selected follow up points.
