Is there a continuing role for prospective observational studies in spine research?

In the accompanying papers, the investigators of the Maine Lumbar Spine Study (MLSS) present the final 10year outcome results of patients with herniated lumbar disc and lumbar spinal stenosis who were treated surgically or nonoperatively. The research design of the MLSS is that of a prospective observational cohort study. Since the initial development of the MLSS in the late 1980s, the field of clinical outcomes research has undergone dramatic change. Randomized Controlled Trials (RCTs) have long been viewed as the gold standard of clinical research when the goal is to compare the efficacy of various treatment options. For many interventions, such as trials of pharmacological agents, adherence to RCT protocols (and their reporting) is expected. For other interventions, such as comparing a surgical and nonsurgical treatment, issues of blinding (for patients, investigators, and treating physicians), willingness to consent to randomization, and postrandomization treatment crossover may limit the scientific validity and practicality of such trials. As a result there have been relatively few RCTs of surgical and nonsurgical interventions in spine disorders. In addition, the methodologies used in clinical research have undergone significant change in the last decade. Previously, many reports of surgical outcomes consisted of small retrospective case series. Baseline data were often missing; patients lost to follow-up were not accounted for or evaluated; validated and standardized questionnaires were not used; results were reported in clinically meaningless terms such as “excellent, good, fair, poor”; and statistical analyses were often lacking. The result was a scientific literature that frequently did not provide information that was scientifically valid. The implications for patient care are obvious. During the 1980s, another important issue began to be recognized. Wennberg and Gittelsohn developed an epidemiological method known as small area variation analysis. They demonstrated that the rates of utilization of most surgical procedures and hospitalizations for medical conditions varied markedly across hospital service areas. The variations could not be explained by differences in patient populations. Instead, it appeared that much of this variation was based on physicians’ preferences for various treatments. Using small area variation analysis, we found marked variations in populationbased rates of lumbar disc surgery in Maine, and we demonstrated that educational feedback of this information to surgeons produced changes in their practice patterns with reductions in high rates of surgery. The publication and dissemination of practice pattern variations and deficiencies in clinical research occurred in a time of rapidly increasing costs of medical care in the United States. A number of leaders in health services research called on the Federal Government to support research to attempt to address these issues. A new organization, the Agency for Health Care Policy and Research (AHCPR) was created by the U.S. Congress. Among its initial efforts, the AHCPR funded a series of Prospective Outcomes Research Teams (PORTs). Among several charges, PORTs were mandated to conduct clinical studies of the “effectiveness” of various medical treatments. Among the initially funded PORTs was the Back Outcomes Assessment Team (BOAT; Principal Investigator, Richard Deyo MD, MPH) The MLSS was one component of the BOAT research agenda. In the years since the AHCPR [now named the Agency for Healthcare Quality and Research (AHRQ)] was created, the quality of clinical research has markedly improved. Journals such as Spine now publish significant numbers of RCTs. A few randomized trials of alternative treatments of disc herniation, spinal stenosis, and spinal fusion have been published, and a large NIH funded multicenter-combined RCT and observational cohort study of surgical and nonoperative treatment of spinal stenosis, degenerative spondylolisthesis, and herniated lumbar disc is ongoing. In addition, the methodological quality of other clinical outcomes research is improving. Except for rare conditions and infrequently performed procedures, retrospective case series are infrequently published by the high quality peer reviewed journals. It is thus reasonable to ask if there is an ongoing role for clinical studies using a prospective observational cohort design. One of the issues underlying the early work of AHCPR was a concern about the “effectiveness” versus“efficacy” of medical treatments. Efficacy research refers to that performed under tightly controlled protocols in large medical centers by experts in the clinical field under study. These are almost always randomized trials, and they are intended to answer the critical question: Is this From the *Center for the Evaluative Clinical Sciences, Dartmouth Medical School, Hanover, NH and †the General Medicine Division and Clinical Epidemiology Unit, Medical Services, Massachusetts General Hospital, Harvard Medical School, Boston, MA. The manuscript submitted does not contain information about medical device(s)/drug(s). Federal funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence and reprint requests to Robert B. Keller, MD, 7 Parkinson Lane, Northport, ME 04849; E-mail: bmwm6@midmaine.com