J Manipulative Physiol Ther. 2005 (Feb); 28 (2): 90–96 ~ FULL TEXT
Charlotte Leboeuf-Yde, DC, MPH, Arndt Grønstvedt, DDS, DC, Jan Arve Borge, DC,
Jakob Lothe, DC, Eli Magnesen, DC, Øyvind Nilsson, DC, Gro Røsok, DC,
Lars-Christian Stig, DC, Kristian Larsen, PT, MPH
Medical Research Unit in Ringkøbing County,
OBJECTIVES: The aims of the study are to describe the low-back pain and disability status at baseline, the fourth visit, and at 3 and 12 months in Norwegian patients treated by chiropractors for persistent low back pain (LBP) and to describe movements between various subgroups over time.
DESIGN: Prospective uncontrolled multicenter study.
METHODS: Self-reported pain was measured with a 0-10 box scale and disability with the revised Oswestry LBP questionnaire. The main outcome measures were mean pain or disability values and numbers of LBP-free patients. LBP status was assessed through patient questionnaires at baseline, the fourth visit, and after 3 and 12 months. STUDY SUBJECTS AND SETTING: Of 205 invited chiropractors, 115 Norwegian chiropractors were each willing to recruit 10 consecutive patients who had LBP for at least 2 weeks at the time of consultation and a minimum of 30 days altogether within the preceding year. The numbers of participants were 875 (baseline), 799 (fourth visit), 598 (3 months), and 512 (12 months).
RESULTS: Considerable improvement was noted between baseline and the fourth visit both for mean values and in numbers of LBP-free patients. There was virtually no further mean improvement up to the third month, whereas the number of LBP-free individuals doubled. At 12 months, no additional improvement was noted, and 80% reported that they had experienced recurrent problems. Less than 1% reported considerable worsening. Severity of symptoms at baseline determined the subsequent outcome, mild symptoms tending to worsen, and severe symptoms tending to improve.
CONCLUSION: The outcome pattern is similar to that found in other clinical studies. Treatment outcome should be measured early with follow-up at 3 rather than at 12 months, because patients will improve or recover quickly but may experience recurring problems. Numbers "cured" appear to be a feasible outcome variable in this type of study population.
Key Indexing Terms: Low back pain, Chiropractic, Treatment outcome, Prognosis, Subacute, Chronic
From the FULL TEXT Article:
In recent years, it has become evident that episodes of nonspecific low back pain (LBP) do not necessarily have the self-limiting course as previously thought. Instead, a high percentage of patients seen in general practice continue to complain of LBP.1, 2 The profiles of patients who improve and do not improve need to be elucidated. In particular, it is important to prevent the persistence of LBP, which is costly and generally agreed to be largely therapy-resistant.
The optimal clinical management of this type of LBP is not known. The choice of treatment is largely based on patients' own choice of therapist, as there are no clear indicative criteria that can direct patients to specific therapies. The clinician's decisions are partially evidence-based but to a large degree governed by his/her professional and subcultural background. Practice patterns are rarely challenged, as it is usually not possible to determine whether treatment was necessary or indeed successful because neither the natural course of LBP nor the prognostic picture is well understood.
Because it is reasonable to assume that nonspecific LBP is made up of specific subgroups, there is a need to conduct trials for specific subgroups of patients to determine which of the different therapeutic methods (if any) is best suited to particular subgroups.3 Absence of generally accepted specific classic pathoanatomic diagnostic subgroups, however, makes such studies difficult.
For these reasons, a research program is underway in Scandinavia, where several research teams work in collaboration toward a better understanding of this area. As part of this program, a prospective uncontrolled multicenter study was conducted to describe the LBP and disability status at baseline, the fourth visit, 3 months, and 12 months in patients treated by chiropractors for persistent LBP. Another aim was to describe movements over time between various subgroups in relation to pain and disability.
According to this study, most improvement occurs early in the course of treatment, and a large number of patients have relapses during the coming year. This is a prognostic pattern resembling that of other types of LBP patients receiving other types of therapy, [1, 2, 9-16] including osteopathic spinal manipulative therapy. 
If the outcome were mainly explained by the natural course, improvement would be expected to occur in relation to the duration from the onset of symptoms rather than the onset of treatment. Since most of the improvement occurs early in the course could mean that the treatment does have an effect.
Another finding that seems to support the possibility of a real positive treatment effect is that a much larger proportion of patients can be classified as LBP-free throughout the study than those whose condition worsened to the extreme degree of “definitely worse.” A closer look at our data revealed that regression toward the mean most likely has a substantial impact on the results, meaning that patients who are bad tend to get better and those who are mildly affected tend to get worse. Patients will usually seek treatment when they are in pain. For the clinician, this makes identification of the regression toward the mean phenomenon difficult. For most clinicians, this argument may come as a surprise, because the usual attitude to outcome would be that improvement is the result of the treatment rather than a mere statistical fluctuation. Furthermore, as a relatively large group of chiropractic patients report immediate postmanipulative improvement at the first clinical encounter, the treatment-effect concept will be underpinned, both for the chiropractor and patient.
In research, the regression toward the mean alerts us to the importance of similarity between study groups in relation to severity of symptoms at baseline, because the group with most “bad” patients would be more likely to move its mean value toward improvement than the group with most “good” patients. This would be particularly crucial in studies with few study subjects.
In our study, the mean Oswestry disability status went from 35 at baseline to 21 at 3 months. These figures are similar to those reported at baseline and the 1-month follow-up in an outcome study on LBP patients treated by chiropractors and general practitioners  and in another chiropractic outcome study of neck and LBP with follow-up at 6 weeks,  whereas no comparison could be made with an osteopathic outcome study of acute and subchronic low back trouble.  However, mean values do not provide information regarding individual successes and failures. Most patients and chiropractors would primarily aim for absence of LBP. Therefore, it is interesting that there were a reasonable number of people who became “LBP-free,” showing this to be a feasible outcome variable in future studies. Apart from being highly clinically relevant, this outcome measure would also make it possible to calculate “the numbers needed to treat” in clinical trials, as recommended by Sackett et al.  Numbers needed to treat is a specification of the number of patients who should be treated before 1 of them actually benefits from the intervention; it is more clinically meaningful than a statement in relation to the overall average improvement for the whole group who received treatment. It would, of course, also be possible to define other clinically relevant levels of improvement (or worsening for that matter) and to count the number of individuals in each treatment group who fulfill these criteria. Also this approach would allow for a number-needed-to-treat calculation.
Interestingly, there was only little further mean improvement at 3 months as compared with the fourth-visit survey, whereas the number of LBP-free individuals almost doubled between these 2 surveys. In a study using mean values as outcome measurements, such a change would go undetected, which shows that the choice of outcome calculations in clinical trials is crucial. As an example, in a randomized controlled trial on neck pain comparing 3 treatment modalities, the estimates of improved pain and physical function at 7 weeks were not significantly different between therapeutic groups when comparing their mean values. However, when counting the number of patients who improved in terms of general improvement, a very large difference emerged. 
Many relapses among patients treated for LBP have been found in other studies [1, 2, 10, 14-16] including 1 on chronic LBP patients treated by chiropractors, with a 1-year relapse rate of approximately 90%.  This is hardly surprising when taking into account the recent insights into LBP, which point to it being a cyclic/persistent condition rather than an occasional well-defined event. This brings into focus the issue of the optimal time for follow-up both from clinical and research perspectives. While a previous pilot study on this type of study population directed us to the fourth treatment as the earliest point in time when it would be suitable to discriminate between recovery and nonrecovery,  it is not known at what time surveillance should stop. Our data, in line with those of others, [10, 11] indicate that a suitable duration for reassessment of initial treatment results should rather be 3 than 12 months, as no further development was noted at 1 year. Nyiendo et al  noted no further improvement after 6 months, which further strengthens our argument.
From a research perspective, the following aspects are important. Treatment outcome should be measured early in the course of treatment and the final follow-up somewhere not too distant in time, because LBP is a disorder that likely reacts quickly to treatment but is of cyclic/recurring nature.
An individual-based outcome, such as numbers of patients who become “LBP-free,” should be used in clinical studies to allow for the number-needed-to-treat calculation. Mean measurements are not recommended.
In clinical studies, there is a need to control for the regression toward the mean, for example, by ensuring that patient groups are equally severely affected or by performing several baseline measurements.
From a clinical perspective, the following information is important. Patients improve early in the course of treatment. About two thirds improve by the fourth visit and almost one third of patients can be classified as LBP-free at 3 months. It is necessary to take the patients' outcome reports with a grain of salt and to remember the regression toward the mean effect (ie, people who are very ill tend to get better and those who are well tend to get worse).
During the ensuing year, most patients have relapses, often unbeknown to the chiropractor.
By far, most patients are satisfied with the treatment, and patients' satisfaction is associated with their LBP status at the fourth visit rather than their LBP status at 12 months, indicating that patients probably do not hold the chiropractor responsible for the return of symptoms.
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