***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Prognosis studies are investigations of future events or the evaluation of associations between risk factors and health outcomes in population s of patients ( 1 ) . The results of such studies improve our underst and ing of the clinical course of a disease and assist clinicians in making informed decisions about how best to manage patients . Prognostic research also informs the design of intervention studies by helping define subgroups of patients who may benefit from a new treatment and by providing necessary information about the natural history of a disorder ( 2 ) . There has recently been a rapid increase in the use of systematic review methods to synthesize the evidence on research questions related to prognosis . It is essential that investigators conducting systematic review s thoroughly appraise the method ologic quality of included studies to be confident that a study 's design , conduct , analysis , and interpretation have adequately reduced the opportunity for bias ( 3 , 4 ) . Caution is warranted , however , because inclusion of method ologically weak studies can threaten the internal validity of a systematic review ( 4 ) . This follows abundant empirical evidence that inadequate attention to biases can cause invalid results and inferences ( 5 - 9 ) . However , there is limited consensus on how to appraise the quality of prognosis studies ( 1 ) . A useful framework to assess bias in such studies follows the basic principles of epidemiologic research ( 10 , 11 ) . We focus on 6 areas of potential bias : study participation , study attrition , prognostic factor measurement , confounding measurement and account , outcome measurement , and analysis . The main objectives of our review of review s are to describe methods used to assess the quality of prognosis studies and to describe how well current practice s assess potential biases . Our secondary objective is to develop recommendations to guide future quality appraisal , both within single studies of prognostic factors and within systematic review s of the evidence . We hope this work facilitates future discussion and research on biases in prognosis studies and systematic review s. Methods Literature Search and Study Selection We identified systematic review s of prognosis studies by search ing MEDLINE ( 1966 to October 2005 ) using the search strategy recommended by McKibbon and colleagues ( 12 ) . This strategy combines broad search terms for systematic review s ( systematic review .mp ; meta- analysis .mp ) and a sensitive search strategy for prognosis studies ( cohort , incidence , mortality , follow-up studies , prognos * , predict * , or course ) . We also search ed the reference lists of included review s and method ologic papers to identify other relevant publications . We restricted our search to English- language publications . One review er conducted the search and selected the studies . Systematic review s , defined as review s of published studies with a comprehensive search and systematic selection , were included if they assessed the method ologic quality of the included studies by using 1 or more explicit criteria . We excluded studies if they were meta-analyses of independent patient data only , if their primary goal was to investigate the effectiveness of an intervention or specific diagnostic or screening tests , or if they included studies that were not done on humans . Data Extraction and Synthesis Individual items included in the quality assessment of the systematic review s were recorded as they were reported in the publication ( that is , the information that would be available to readers and future review ers ) . We review ed journal Web sites and contacted the authors of the systematic review s for additional information when authors made such an offer in their original papers . When review s assessed different study design s by using different sets of quality items , we extracted only those items used to assess cohort studies . We constructed a comprehensive list of distinct items that the review s used to assess the quality of their included studies . The full text of each review was screened . All items used by the review authors to assess the quality of studies were extracted into a computerized spreadsheet by 1 review er . Two experienced review ers , a clinical epidemiologist and an epidemiologist , independently synthesized the quality items extracted from the prognosis review s to determine how well the systematic review s assessed potential biases . We did this in 3 steps : 1 ) identified distinct concepts or domains addressed by the quality items ; 2 ) grouped each extracted quality item into the appropriate domain or domains ; and 3 ) identified the domains necessary to assess potential biases in prognosis studies . We then used this information to assess how well the review s ' quality assessment included items from the domains necessary to assess potential biases . After completing each of the first 3 steps , the review ers met to attempt to reach a consensus . The consensus process involved each review er presenting his or her observations and results , followed by discussion and debate . A third review er was available in cases of persistent disagreement or uncertainty . In the first step , all domains addressed by the quality items were identified . The first review er iteratively and progressively defined the domains as items were extracted from the included review s. The second review er defined domains from a r and om list of all extracted quality items . Limited guidance was provided to the review ers so that their assessment s and definitions of domains would be independent . The review ers agreed on a final set of domains that adequately and completely defined all of the extracted items . In the second step , review ers independently grouped each extracted item into the appropriate domains . Review ers considered each extracted item by asking , What is each particular quality item addressing ? or What are the review 's authors getting at with the particular quality assessment item ? . Items were grouped into the domain or domains that best represented the concepts being addressed . For example , the extracted items at least 80 % of the group originally identified was located for follow-up and follow-up was sufficiently complete or does n't jeopardize validity were each independently classified by both review ers as assessing the domain completeness of follow-up adequate , whereas the extracted item quantification and description of all subjects lost to follow-up was classified as assessing the domain completeness of follow-up described . In the third step , we identified the domains necessary to assess potential biases . Each review er considered the ability of the identified domains to adequately address , at least in part , 1 of the following 6 potential biases : 1 ) study participation , 2 ) study attrition , 3 ) prognostic factor measurement , 4 ) confounding measurement and account , 5 ) outcome measurement , and 6 ) analysis . Domains were considered to adequately address part of the framework if information garnered from that domain would inform the assessment of potential bias . For example , both review ers judged that the identified domain study population represents source population or population of interest assessed potential bias in a prognosis study , whereas the domain research question definition did not , although the latter is an important consideration in assessing the inclusion of studies in a systematic review . Finally , on the basis of our previous ratings , we looked at whether each review included items from the domains necessary to assess the 6 potential biases . We calculated the frequency of systematic review s by assessing each potential bias and the number of review s that adequately assessed bias overall . From this systematic synthesis , we developed recommendations for improving quality appraisal in future systematic review s of prognosis studies . We used Microsoft Access and Excel 2002 ( Microsoft Corp. , Redmond , Washington ) for data management and SAS for Windows , version 9.1 ( SAS Institute , Inc. , Cary , North Carolina ) for descriptive statistics . Role of the Funding Sources The funding sources , the Canadian Institutes of Health Research , the Canadian Chiropractic Research Foundation , the Ontario Chiropractic Association , and the Ontario Ministry of Health and Long Term Care , did not have a role in the collection , analysis , or interpretation of the data or in the decision to su bmi t the manuscript for publication . Results We identified 1384 potentially relevant articles . Figure 1 shows a flow chart of studies that were included and excluded . Figure 2 shows the number of review s identified by year of publication . We excluded 131 systematic review s of prognosis studies that did not seem to include any quality assessment of the included studies ; this represented 44 % of prognosis review s. We included 163 review s of prognosis studies in our analysis ( 13 - 175 ) . The most common topics were cancer ( 15 % ) , musculoskeletal disorders and rheumatology ( 13 % ) , cardiovascular ( 10 % ) , neurology ( 10 % ) , and obstetrics ( 10 % ) . Other review s included a wide range of health and health care topics . Sixty-three percent of the review s investigated the association between a specific prognostic factor and a particular outcome ; the remainder investigated multiple prognostic factors or models . The number of primary studies included in each systematic review ranged from 3 to 167 ( median , 18 [ interquartile range , 12 to 31 ] ) . A complete description of the included review s is available from the authors on request . Figure 1 . Flow diagram of inclusion and exclusion criteria of systematic review s. Figure 2 . Number of systematic review s of prognosis studies identified over time . Quality Items One hundred fifty-three review s provided adequate detail to allow extraction of quality items . Eight hundred eighty-two distinct quality items were extracted from the review s. Most review s developed their own set of quality items , with only a few applying criteria from previous review s. Most quality items OBJECTIVE To determine the prevalence and characteristics of fibromyalgia in the general population . METHODS A r and om sample of 3,006 persons in Wichita , KS , were characterized according to the presence of no pain , non-widespread pain , and widespread pain . A sub sample of 391 persons , including 193 with widespread pain , were examined and interviewed in detail . RESULTS The prevalence of fibromyalgia was 2.0 % ( 95 % confidence interval [ 95 % CI ] 1.4 , 2.7 ) for both sexes , 3.4 % ( 95 % CI 2.3 , 4.6 ) for women , and 0.5 % ( 95 % CI 0.0 , 1.0 ) for men . The prevalence of the syndrome increased with age , with highest values attained between 60 and 79 years ( > 7.0 % in women ) . Demographic , psychological , dolorimetry , and symptom factors were associated with fibromyalgia . CONCLUSION Fibromyalgia is common in the population , and occurs often in older persons . Characteristic features of fibromyalgia -- pain threshold and symptoms -- are similar in community and clinic population s , but overall severity , pain , and functional disability are more severe in the clinic population Pain is a syndrome characterized by several neurophysiological changes including that of the autonomic nervous system . Chronic low back pain ( LBP ) is a major health problem and is a frequent reason for using unconventional therapies especially acupuncture . This study was conducted to evaluate the autonomic status and pain profile in chronic LBP patients and to observe the effect of electro acupuncture therapy . Chronic LBP patients ( n=60 ) were recruited from the Department of Orthopaedics , GTB Hospital , Delhi . Age and sex matched healthy volunteers were selected as controls ( n=30 ) . Following a written consent , LBP patients were r and omly allocated into two study groups - Group A received 10 sittings of electro acupuncture , on alternate days , at GB and UB points selected for back pain , while the Group B received a conventional drug therapy in the form of oral Valdecoxib together with supervised physiotherapy . Controls were assessed once while the patients were assessed twice , before and after completion of the treatment program ( 3 weeks ) . The autonomic status was studied with non-invasive cardiovascular autonomic function tests which included E : I ratio , 30:15 ratio , postural challenge test and sustained h and grip test . Pain intensity was measured with the visual analogue scale ( VAS ) and the global perceived effect ( GPE ) . Statistical analysis was performed using repeated measure 's ANOVA with Tukey 's test . Pain patients showed a significantly reduced vagal tone and increased sympathetic activity as compared to the controls ( P<0.05 to P<0.001 in different variables ) . Following treatment , both the study groups showed a reduction in vagal tone together with a decrease in the sympathetic activity . There was also a considerable relief of pain in both groups , however , the acupuncture group showed a better response ( P<0.01 ) . We conclude that there is autonomic dysfunction in chronic LBP patients . Acupuncture effectively relieves the pain and improves the autonomic status and hence can be used as an alternative/additive treatment modality in these cases The aim of the present study was to investigate reactions in trapezius muscle blood flow ( MBF ) , muscle activity , heart rate variability ( HRV ) and systemic blood pressure ( BP ) to autonomic tests in subjects with chronic neck – shoulder pain and healthy controls . Changes in muscle activity and blood flow due to stress and unfavourable muscle loads are known underlying factors of work-related muscle pain . Aberration of the autonomic nervous system ( ANS ) is considered a possible mechanism . In the present study , participants ( n = 23 Pain , n = 22 Control ) performed autonomic tests which included a resting condition , static h and grip test ( HGT ) at 30 % of maximal voluntary contraction , a cold pressor test ( CPT ) and a deep breathing test ( DBT ) . HRV was analysed in time and frequency domains . MBF and muscle activity were recorded from the upper trapezius muscles using photoplethysmography and electromyography ( EMG ) . The pain group showed reduced low frequency-HRV ( LF ) and SDNN during rest , as well as a blunted BP response and increased LF-HRV during HGT ( ∆systolic 22 mm Hg ; ∆LF(nu ) 27 % ) compared with controls ( ∆systolic 27 ; ∆LF(nu ) 6 % ) . Locally , the pain group had attenuated trapezius MBF in response to HGT ( Pain 122 % Control 140 % ) with elevated trapezius EMG following HGT and during CPT . In conclusion , only HGT showed differences between groups in systemic BP and HRV and alterations in local trapezius MBF and EMG in the pain group . Findings support the hypothesis of ANS involvement at systemic and local levels in chronic neck – shoulder pain UNLABELLED Several case-control studies have been conducted that examine the association between autonomic variables and persistent pain conditions ; however , there is a surprising dearth of published studies in this area that have focused on temporom and ibular disorders ( TMD ) . The current study presents autonomic findings from the baseline case-control study of the OPPERA ( Orofacial P 
    Output:
    
High heterogeneity aside , pooled results from the meta-analyses reflected a consistent , moderate-to-large effect of decreased high-frequency HRV in chronic pain , implicating a decrease in parasympathetic activation .
These effects were heavily influenced by fibromyalgia studies .