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    <title>Heintjes, E.M.</title>
    <link>http://repub.eur.nl/res/aut/9308/</link>
    <description>List of Publications</description>
    <language>en</language>
    <image>
      <url>http://repub.eur.nl/static-eur/img/logo.png</url>
      <title>RePub, Erasmus University Rotterdam</title>
      <link>http://repub.eur.nl</link>
    </image>
    <item>
      <title>Predictors of persistent complaints after a knee injury in primary care (Article)</title>
      <link>http://repub.eur.nl/res/pub/39367/</link>
      <pubDate>2012-08-01T00:00:00Z</pubDate>
      <description>Background: Prognosis of persistent complaints after knee injury is based on secondary care populations. In a primary care setting, however, no studies have addressed this issue. Aim: To identify possible predictors of persistent complaints 1 year after a knee injury. These predictors are important for guiding the GP's therapeutic management, and giving advice to patients about work and/or sports-related activities. Design and setting: Primary care prospective cohort study with a 1- year follow-up period in five municipalities in the southwest region of the Netherlands. Method: Patients who were eligible were recruited to the study by a GP research network with around 84 000 patients and 40 participating GPs. A total of 134 patients (aged 18-65 years) who consulted their GP within 5 weeks after a knee injury entered the study. Follow-up after 1 year was conducted in 122 patients. The main outcome was persistent complaints 1 year after injury; possible predictors for these complaints were obtained with a questionnaire, a physical examination, and magnetic resonance imaging (MRI), according to a standardised protocol. Results: After 1 year, of the 122 available patients, 21 (17%) reported persistent complaints and 101 (83%) reported full recovery ormajor improvement. In this study being aged &gt;40 years had a significant association (P&lt;0.05) with persistent complaints (odds ratio 8.0, 95% confidence interval 2.1 to 30.5). Physical examination and MRI findings revealed no predictors that were associated with these complaints. Conclusion: Being aged &gt;40 years was the only determinant with a significant association with persistent complaints. As physical examination and MRI had no predictive value, they are not recommended for prognosis of persistent complaints. </description>
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      <title>Dupuytren's contracture: A retrospective database analysis to determine hospitalizations in the Netherlands (Article)</title>
      <link>http://repub.eur.nl/res/pub/32900/</link>
      <pubDate>2011-10-13T00:00:00Z</pubDate>
      <description>Background: Dupuytren's contracture is a condition of the palmar fascia involving contractures of the fascia and skin in the hand. Current treatment for Dupuytren's contracture is mainly limited to surgery. In the Netherlands, little is known about the prevalence of Dupuytren's contracture. In this study we determined the prevalence of patients with a hospitalization for Dupuytren's contracture in the Netherlands and characterized their (re)hospitalizations. Methods. From the PHARMO database, which consists of multiple observational databases linked on a patient level, all patients hospitalized for Dupuytren's contracture between 2004 and 2007 were included in the source population (ICD-9-CM code 728.6). Numbers from this source population were used to provide estimates of hospitalizations for Dupuytren's contracture in the Netherlands. Patients with a medical history in the PHARMO database of at least 12 months before their hospitalization were included in the study cohort and followed until end of data collection, death, or end of study period, whichever occurred first. Type of admission, length of stay, recorded procedures, treating specialty, number of rehospitalizations for Dupuytren's contracture, and time to first rehospitalization were assessed. Results: Of 3, 126 patients included in the source population, 3, 040 were included in the study population. The overall prevalence of patients with a hospitalization for Dupuytren's contracture was 0.04%, with the highest prevalence (0.25%) among 60-79 year old males. The majority (85%) of all hospitalizations were day-case admissions. Of the admitted inpatients (15%) the majority (81%) had one overnight stay in the hospital. The most common recorded procedure was fasciectomy (87%) and 78% of patients was treated by a plastic surgeon. During a median (IQR) follow-up of 2.9 (1.8-4.0) years, 523 patients were rehospitalized for Dupuytren's contracture. The median (IQR) time to first rehospitalization was 0.8 (0.4-1.9) years. Conclusions: This study is a first exploration of Dupuytren's contracture in the Netherlands based on hospitalizations, showing a prevalence of 0.25% among 60-79 year old males. Future studies should also address outpatient procedures to get a complete picture of the treatment of Dupuytren's contracture. In addition, patients not yet treated should be included to be able to estimate the prevalence of Dupuytren's contracture. </description>
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      <title>Diagnostic accuracy of history taking and physical examination for assessing anterior cruciate ligament lesions of the knee in primary care (Article)</title>
      <link>http://repub.eur.nl/res/pub/20762/</link>
      <pubDate>2010-09-01T00:00:00Z</pubDate>
      <description>Abstract

OBJECTIVE: To assess the diagnostic accuracy of history taking and physical examination for assessing anterior cruciate ligament (ACL) lesions in primary care.

DESIGN: Cross-sectional diagnostic study.

SETTING: Primary care.

PARTICIPANTS: Patients (N=134; age, 18-65y) who consulted their general practitioner (GP) within 5 weeks after injury.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Index tests were obtained with a questionnaire and physical examination. Magnetic resonance imaging (MRI) was used as the reference test. Logistic regression analysis was used to determine associations with ACL lesions. Diagnostic accuracy was determined by calculating sensitivity (Se), specificity (Sp), predictive values, and likelihood ratio (LR).

RESULTS: MRI showed an ACL lesion in 28 of 134 included patients. "Effusion," "popping sensation," "giving way," and "anterior drawer test (ADT)" showed associations with an ACL lesion (P&lt;.05). Popping sensation showed Se, Sp, positive predictive value (PPV), and positive LR (LR(+)) of .63, .73, .39, and 2.3, respectively. Combining determinants from history taking (2 of 3 positive results regarding effusion, popping sensation, and giving way) improved diagnostic accuracy (Se, .71; Sp, .71; PPV, .42; and LR(+), 2.5). The ADT added diagnostic accuracy to these combinations (Se, .63; Sp, .85; PPV, .52; and LR(+), 4.2).

CONCLUSIONS: ACL lesions are seen frequently. Based on history taking (effusion, popping sensation, and/or giving way) and physical examination (ADT), GPs can screen for ACL lesions in primary care.</description>
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      <title>Glycemic control and long-acting insulin analog utilization in patients with type 2 diabetes (Article)</title>
      <link>http://repub.eur.nl/res/pub/19709/</link>
      <pubDate>2010-04-01T00:00:00Z</pubDate>
      <description>Introduction: The objective was to compare glycemic control, insulin utilization, and body weight in patients with type 2 diabetes (T2D) initiated on insulin detemir (IDet) or insulin glargine (IGlar) in a real-life setting in the Netherlands. Methods: Insulin-naïve patients with T2D, starting treatment with IDet or IGlar between January 1, 2004 and June 30, 2008, were selected from the PHARMO data network. Glycemic control (hemoglobin A1c [HbA1c]), target rates (HbA1c &lt;7%), daily insulin dose, and weight gain were analyzed comparing IDet and IGlar for patients with available HbA1c levels both at baseline and at 1-year follow-up. Analysis of all eligible patients (AEP) and a subgroup of patients without treatment changes (WOTC) in the follow-up period were adjusted for patient characteristics, propensity scores, and baseline HbA1c. Results: A total of 127 IDet users and 292 IGlar users were included in the WOTC analyses. The mean HbA1c dropped from 8.4%-8.6% at baseline to 7.4% after 1 year. Patients at HbA1c goal increased from 9% at baseline to 32% for IDet and 11% to 35% for IGlar, which was not significantly different (OR 0.75, 95% CI 0.46, 1.24). Weight gain (n=90) was less among IDet users (+0.4kg) than among IGlar users (+1.1kg), albeit not significant. The AEP analysis (252 IDet + 468 IGlar users) showed similar results with 33%-36% at goal (OR 0.81, 95% CI 0.57, 1.16), and median daily insulin doses of 25 IU/day (P=0.70). Conclusion: There was no significant difference between users of IDet and IGlar with respect to glycemic control and insulin dose in a real-life setting. The low proportion of patients on target at baseline may indicate that insulin therapy is initiated too late. Moreover, the observation that one-third of the patients reached HbA1c target at follow-up may indicate that basal insulin analogs are not titrated intensively enough.</description>
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      <title>Outcome of knee injuries in general practice: 1-year follow-up (Article)</title>
      <link>http://repub.eur.nl/res/pub/20765/</link>
      <pubDate>2010-02-01T00:00:00Z</pubDate>
      <description>Abstract

BACKGROUND: Knee injuries may lead to pain and to functional limitations in the activities of daily living. Patients with knee injuries are frequently seen in general practice; however, the outcome and management in these patients is not known.

AIM: To assess the outcome and management of knee injuries at 12 months' follow-up in general practice.

DESIGN OF STUDY: A prospective observational cohort study with a 1-year follow-up.

SETTING: Primary health care.

METHOD: Adult patients consulting their GP after knee injury (n = 134) participated in the cohort. A magnetic resonance imaging scan was carried out and patients were diagnosed as either no lesion or an isolated meniscal tear, an isolated collateral or cruciate ligament lesion, or a combination. Follow-up questionnaires were filled in up to 12 months' follow-up.

RESULTS: At 12 months' follow-up, 34 patients reported full recovery and 67 patients reported major improvement. At baseline, 37 patients (28%) were referred to physical therapy and 17 patients (13%) were referred to secondary care. During 1 year of follow-up, another 21 referrals to physical therapy and 11 referrals to secondary care took place. The pain severity decreased the most, and the Lysholm knee score increased in the majority of patients during the first 3 months after injury. In total, 18 arthroscopies were performed in 15 patients. One patient underwent an anterior cruciate ligament reconstruction.

CONCLUSION: The vast majority of patients report clinically relevant recovery. There is no clear difference in outcomes between patients with meniscal tears or ligament lesions and patients without these diagnoses.</description>
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      <title>Determination of non-treatment with statins of high risk patients in the Netherlands (Article)</title>
      <link>http://repub.eur.nl/res/pub/27995/</link>
      <pubDate>2010-02-01T00:00:00Z</pubDate>
      <description>Objective: To determine in the Netherlands what proportions of high risk patients with established cardiovascular disease (CVD) or diabetes mellitus type 2 (DM2) who were not treated with statins on 1 January 2007 and which characteristics were associated with non-treatment. Methods: From the IPCI GP database patients were selected who were registered with a GP on 1 January 2007 who had a history of either CVD (CVD patients), DM2 (diabetics) or both (diabetics with CVD). The proportion of patients using statins around 1 January 2007 was determined. Associations of patient characteristics with non-treatment were quantified (CVD patients and diabetics only). Results: In all, 19 628 CVD patients, 5006 diabetics and 3767 diabetics with CVD were identified. Of these patients 71, 54 and 45, respectively did not use statins. These proportions were similar in the subgroups of patients with recent LDL-C measurements. Among these subgroups the vast majority of non-treated patients was eligible for statin treatment (LDL-C &gt;2.5mmol/l). The proportion of statin-treated patients was larger among diabetics than among CVD patients. Among CVD patients, female gender, age below 40 years, living in a deprived area, a history of CVD of less than 1 year and arrhythmia were significantly associated with non-treatment. Among diabetics, significant associations were: living in a deprived area and specialist visits in the previous year. In 2003, treatment rates among diabetics were lower, but among CVD patients they were similar. This suggests that the higher treatment rates among diabetics compared to CVD patients in 2007 may be the result of disease-management programmes introduced for diabetics in 2004. Conclusion: The majority of patients with established CVD or DM2 were not treated with statins on 1 January 2007. Eligibility for statin treatment may have been overestimated due to unavailability of cholesterol levels among many non-treated patients. Implementation of care programmes for CVD patients may increase treatment rates among eligible CVD patients. </description>
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      <title>Supervised exercise therapy versus usual care for patellofemoral pain syndrome: an open label randomised controlled trial. (Article)</title>
      <link>http://repub.eur.nl/res/pub/24888/</link>
      <pubDate>2009-11-24T00:00:00Z</pubDate>
      <description>OBJECTIVE: To assess the effectiveness of supervised exercise therapy compared with usual care with respect to recovery, pain, and function in patients with patellofemoral pain syndrome. DESIGN: Open label randomised controlled trial. SETTING: General practice and sport physician practice. PARTICIPANTS: Patients with a new episode of patellofemoral pain syndrome recruited by their general practitioner or sport physician. INTERVENTIONS: The intervention group received a standardised exercise programme for 6 weeks tailored to individual performance and supervised by a physical therapist, and were instructed to practise the tailored exercises at home for 3 months. The control group were assigned usual care, which comprised a "wait and see" approach of rest during periods of pain and refraining from pain provoking activities. Both the intervention group and the control group received written information about patellofemoral pain syndrome and general instructions for home exercises. MAIN OUTCOME MEASURES: The primary outcomes were self reported recovery (7 point Likert scale), pain at rest and pain on activity (0-10 point numerical rating scale), and function (0-100 point Kujala patellofemoral score) at 3 months and 12 months follow-up. RESULTS: A total of 131 participants were included in the study: 65 in the intervention group and 66 in the control group. After 3 months, the intervention group showed better outcomes than the control group with regard to pain at rest (adjusted difference -1.07, 95% confidence interval -1.92 to -0.22; effect size 0.47), pain on activity (-1.00, -1.91 to -0.08; 0.45), and function (4.92, 0.14 to 9.72; 0.34). At 12 months, the intervention group continued to show better outcomes than the control group with regard to pain (adjusted difference in pain at rest -1.29, -2.16 to -0.42; effect size 0.56; pain on activity -1.19, -2.22 to -0.16; effect size 0.54), but not function (4.52, -0.73 to 9.76). A higher proportion of patients in the exercise group than in the control group reported recovery (41.9% v 35.0% at 3 months and 62.1% v 50.8% at 12 months), although the differences in self reported recovery between the two groups were not statistically significant. Predefined subgroup analyses revealed that patients recruited by sport physicians (n=30) did not benefit from the intervention, whereas those recruited by general practitioners (n=101) showed significant and clinically relevant differences in pain and function in favour of the intervention group. CONCLUSION: Supervised exercise therapy resulted in less pain and better function at short term and long term follow-up compared with usual care in patients with patellofemoral pain syndrome in general practice. Exercise therapy did not produce a significant difference in the rate of self reported recovery. TRIAL REGISTRATION: ISRCTN83938749.</description>
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      <title>Comparison of incidences of cardiovascular events among new users of different statins: A retrospective observational cohort study (Article)</title>
      <link>http://repub.eur.nl/res/pub/24936/</link>
      <pubDate>2009-11-01T00:00:00Z</pubDate>
      <description>Objective: To compare incidences of cardiovascular disease (CVD) in general and myocardial infarction (MI) specifically between new users of different statins in daily practice. Design and methodology: Retrospective observational cohort study. Data were obtained from the PHARMO Record Linkage System; the PHARMO database contains pharmacy dispensing records of 3 million patients in the Netherlands registered with community pharmacies, linked to hospitalisation records. The participants were new statin users in the period 2000-2005, excluding patients hospitalised for CVD events in the year prior to start of statin use. Main outcome measures: Adjusted hazard ratios of hospitalisations for CVD (including any type of ischemic heart disease, stroke, or revascularisation procedure) in general, or MI in particular, occurring during use of the initial statin within two years of start of therapy, comparing users of different statins. Results: The mean follow-up duration of 76,147 new statin users (14,530 pravastatin, 27,752 simvastatin, 25,777 atorvastatin, 8088 rosuvastatin) was 55 weeks. Incidence rates of CVD and MI per 100 person years ranged from 0.75 and 0.15 for rosuvastatin to 1.72 and 0.29 for pravastatin. Rosuvastatin users had a lower incidence rate of CVD compared to other statin users in general (28% lower), and simvastatin (29% lower) and pravastatin users (40% lower) in particular. The difference with atorvastatin was not statistically significant. Since this was not a prospective randomised study, there is the potential for unobserved risk factors to be responsible for some of the differences observed. Conclusion: Compared to other statin users without recent prior cardiovascular events, the incidence of fatal and nonfatal CVD in this retrospective observational cohort study was 28% lower among rosuvastatin users. </description>
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      <title>Longitudinal and cross-sectional validity of the DynaPort® Knee Test in adults with nontraumatic knee complaints in general practice (Article)</title>
      <link>http://repub.eur.nl/res/pub/29822/</link>
      <pubDate>2008-12-01T00:00:00Z</pubDate>
      <description>Objective: The aim of the study was to determine the cross-sectional and longitudinal validity of a performance-based assessment of knee function, DynaPort®KneeTest (DPKT), in first-time consulters with nontraumatic knee complaints in general practice. Methods: Patients consulting for nontraumatic knee pain in general practice aged &gt;18 years were enrolled in the study. At baseline and 6-months follow-up knee function was assessed by questionnaires and the DPKT; a physical examination was also performed at baseline. Hypothesis testing assessed the cross-sectional and longitudinal validity of the DPKT. Results: Eighty-seven patients were included for the DPKT, 86 were available for analysis. The studied population included 44 women (51.2%), the median age was 54 (range 18-81) years. At follow up, 77 patients (89.5%) were available for the DPKT. Only 3 out of 11 (27%) predetermined hypotheses concerning the cross-sectional and longitudinal validity were confirmed. Comparison of the general practice and secondary care population showed a major difference in baseline characteristics, DynaPort Knee Score, internal consistency, and hypotheses confirmation concerning the construct validity. Conclusion: The validity of the DPKT could not be demonstrated for first-time consulters with nontraumatic knee complaints in general practice. Measurement instruments developed and validated in secondary care are therefore not automatically also valid in primary care setting. </description>
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      <title>Lysholm scale and WOMAC index were responsive in prospective cohort of young general practice patients (Article)</title>
      <link>http://repub.eur.nl/res/pub/29839/</link>
      <pubDate>2008-05-01T00:00:00Z</pubDate>
      <description>Objective: To determine the construct validity and responsiveness of the Lysholm knee scoring scale and the WOMAC osteoarthritis index in adolescents and young adults with knee complaints in general practice. Study Design and Setting: In the framework of a prospective cohort study with 1-year follow-up, we included 314 patients aged 12-35 years consulting the general practitioner for incident knee complaints. Subgroup analyses of traumatic and nontraumatic knee complaints and of adolescents and adults were performed. Results: Construct validity was adequate for both questionnaires both in traumatic and nontraumatic patients (aged 12-35) and in adolescents (12-17) and young adults (18-35). Effect size (ES) and standardized response mean (SRM) for both Lysholm and WOMAC global scores were moderate in nontraumatic patients and high in traumatic patients. Guyatt's responsiveness statistic was high in both subpopulations. Adolescents showed high responsiveness with all measures on the Lysholm scale, and moderate (Guyatt's statistic) to high responsiveness (ES and SRM) on the WOMAC index. Young adults showed high responsiveness with all measures on both instruments. Conclusion: Although neither of the scales was developed for use in adolescents and young adults in general practice, both scales show adequate responsiveness, content, and construct validity in this population. </description>
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      <title>Diagnostic value of history-taking and physical examination for assessing meniscal tears of the knee in general practice (Article)</title>
      <link>http://repub.eur.nl/res/pub/15186/</link>
      <pubDate>2008-01-01T00:00:00Z</pubDate>
      <description>OBJECTIVE: To assess the diagnostic value of history-taking and physical examination of meniscal tears in general practice. DESIGN: An observational study determining diagnostic values (sensitivity, specificity, predictive value, and likelihood ratios). SETTING: General practice. PATIENTS: Consecutive patients aged 18 to 65 years with a traumatic knee injury who consulted their general practitioner within 5 weeks after trauma. ASSESSMENT: Participating patients filled out a questionnaire (history-taking) followed by a standardized physical examination. MAIN OUTCOME: Assessment of meniscal tears was determined by means of magnetic resonance imaging (MRI) and was performed blinded for the results of physical examination and history-taking. RESULTS: Of the 134 patients included in this study, 47 had a meniscal tear. From history-taking, the determinants "age over 40 years," "continuation of activity impossible," and "weight-bearing during trauma" indicated an association with a meniscal tear after multivariate logistic regression analysis, whereas from physical examination only "pain at passive flexion" indicated an association. These associated determinants from history-taking showed some diagnostic value; the positive likelihood ratio (LR+) reached up to 2.0 for age over 40 years, whereas the isolated test pain at passive flexion from physical examination has less diagnostic value, with an LR+ of 1.3. Combining determinants from history-taking and physical examination improved the diagnostic value with a maximum LR+ of 5.8; however, this combination only applied to a limited number of patients. CONCLUSION: History-taking has some diagnostic value, whereas physical examination did not add any diagnostic value for detecting meniscal tears in general practice.</description>
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      <title>Non-traumatic knee complaints in adolescents and young adults in general practice (Doctoral Thesis)</title>
      <link>http://repub.eur.nl/res/pub/8555/</link>
      <pubDate>2006-11-23T00:00:00Z</pubDate>
      <description>Knee complaints are a frequent reason for consultation in general practice and constitute 
a specific set of patients compared to secondary care patient populations. However, 
information to base treatment decisions on is generally derived from specialistic settings. 
Our cohort study is aimed at collecting knowledge about disease burden and prognosis 
of knee complaints presenting in general practice 
Chapter 2 describes the design and methods of the HONEUR knee cohort and 
addresses the possibility of selective patient recruitment. From October 2001 to October 
2003 40 GPs recruited consecutive patients consulting for incident knee complaints. 
Patients were followed-up for one year with three monthly questionnaires. At baseline 
and after one year follow-up the patients underwent a physical examination. Primary 
outcome measure was the patient's reported recovery after one year. Pain and functional 
disability were assessed every 3 months to determine the course of the knee complaints 
during the year follow-up. 
The cohort is divided into traumatic and non-traumatic knee complaints. The non-
traumatic knee complaints are then divided in patients aged 12 through 35 and 36 years 
and over. This subdivision is based on the predominance of patellofemoral complaints in 
the younger age group, and the shift to osteoarthritis as the major complaint starting at 
age 35.</description>
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      <title>The PEX study - Exercise therapy for patellofemoral pain syndrome: design of a randomized clinical trial in general practice and sports medicine [ISRCTN83938749]. (Article)</title>
      <link>http://repub.eur.nl/res/pub/13988/</link>
      <pubDate>2006-03-17T00:00:00Z</pubDate>
      <description>BACKGROUND: Patellofemoral complaints are frequently seen in younger and active patients. Clinical strategy is usually based on decreasing provoking activities as sports and demanding knee activities during work and leisure and reassuring the patient on the presumed good outcome.Exercise therapy is also often prescribed although evidence on effectiveness is lacking.The objective of this article is to present the design of a randomized clinical trial that examines the outcome of exercise therapy supervised by a physical therapist versus a clinically accepted "wait and see" approach (information and advice about the complaints only).The research will address to both effectiveness and cost effectiveness of supervised exercise therapy in patients with patellofemoral pain syndrome (PFPS). METHODS/DESIGN: 136 patients (adolescents and young adults) with patellofemoral pain syndrome are recruited in general practices and sport medicine centers. They will be randomly allocated receiving either 3 months of exercise therapy (or usual care.The primary outcome measures are pain, knee function and perception of recovery after 3 months and 12 months of follow up and will be measured by self reporting.Measurements will take place at baseline, 6 weeks, and 3 monthly until 1 year after inclusion in the study.Secondary outcome measurements include an economic evaluation.A cost-utility analysis will be performed that expresses health improvements in Quality Adjusted Life Years (QALYs) and incorporates direct medical costs and productivity costs DISCUSSION: This study has been designed after reviewing the literature on exercise therapy for patellofemoral pain syndrome. It was concluded that to merit the effect of exercise therapy a trial based on correct methodological concept needed to be executed.The PEX study is a randomized clinical trial where exercise therapy is compared to usual care. This trial started in April 2005 and will finish in June 2007. The first results will be available around December 2007.</description>
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      <title>Knee disorders in primary care: design and patient selection of the HONEUR knee cohort. (Article)</title>
      <link>http://repub.eur.nl/res/pub/13893/</link>
      <pubDate>2005-08-23T00:00:00Z</pubDate>
      <description>BACKGROUND: Knee complaints are a frequent reason for consultation in general practice. These patients constitute a specific population compared to secondary care patients. However, information to base treatment decisions on is generally derived from specialistic settings. Our cohort study is aimed at collecting knowledge about prognosis and prognostic factors of knee complaints presented in a primary care setting. This paper describes the methods used for data collection, and discusses potential selectiveness of patient recruitment. METHODS: This is a descriptive prospective cohort study with one-year follow-up. 40 Dutch GPs recruited consecutive patients with incident knee complaints aged 12 years and above from October 2001 to October 2003. Patients were assessed with questionnaires and standardised physical examinations. Additional measurements of subgroups included MRI for recent knee traumas and device assessed function measurements for non-traumatic patients. After the inclusion period we retrospectively searched the computerized medical files of participating GPs to obtain a sample to determine possible selective recruitment. We assessed differences in proportions of gender, traumatic onset of injury and age groups between participants and non-participants using Odds Ratios (OR) and 95% confidence intervals. RESULTS: We recruited 1068 patients. In a sample of 310 patients visiting the GP, we detected some selective recruitment, indicating an underrepresentation of patients aged 12 to 35 years (OR 1.70; 1.15-2.77), especially among men (OR 2.16; 1.12-4.18). The underrepresentation of patients with traumatic onset of injury was not statistically significant. CONCLUSION: This cohort is unique in its size, setting, and its range of both age and type of knee complaints. We believe the detected selective recruitment is unlikely to introduce significant bias, as the cohort will be divided into subgroups according to age group or traumatic onset of injury for future analyses. However, the underrepresentation of men in the age group of 12 to 35 years of age warrants caution. Based on the available data, we believe our cohort is an acceptable representation of patients with new knee complaints consulting the GP, and we expect no problems with extrapolation of the results to the general Dutch population.</description>
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