Biomedical subjects

Dirk L Knol

Publications and source records attributed to Dirk L Knol.

29 records · Page 2Linked to original sources

PubMed2005

Retinoblastoma: MR imaging parameters in detection of tumor extent.

PURPOSE: To assess diagnostic accuracy of preoperatively performed magnetic resonance (MR) imaging for detection of tumor extent in a large patient population with histopathologically proved retinoblastoma. MATERIALS AND METHODS: Local ethics committee approval and informed consent were not required for retrospective review of patients' images and records. Fifty-eight eyes in 28 girls (mean age, 21 months; range, 2-59 months) and 28 boys (mean age, 24 months; range, 2-76 months) with retinoblastoma were retrospectively reviewed by one radiologist on unenhanced T1-weighted, dual-echo T2-weighted, and gadolinium-enhanced T1-weighted MR images. MR imaging parameters such as growth pattern, anterior chamber hyperintensity, and involvement of choroid, ciliary body, optic nerve, sclera, orbital fat, and pineal gland were determined. Tumor volume was measured and correlated to metastatic risk factors. Imaging and pathologic findings were compared. Statistical analysis was performed by using logistic regression with log likelihood ratio chi(2) test or Fisher exact test. RESULTS: Choroidal invasion was suspected with MR imaging in 21 eyes; findings were false-positive in 13 eyes and false-negative in three (73% sensitivity, 72% specificity, 72% accuracy). Anterior chamber hyperintensity on T1-weighted MR images obtained after contrast agent administration correlated well with clinical presence of reactive neovascular processes. MR imaging findings were true-positive in 21 of 32 eyes with proved prelaminar optic nerve invasion (66% sensitivity) and false-positive in one (96% specificity, 79% accuracy). Postlaminar optic nerve invasion was correctly detected in two eyes; in two other eyes, this metastatic risk factor was missed (50% sensitivity, 100% specificity, 97% accuracy). Scleral and extrascleral tumor invasion were correctly excluded in all eyes. Tumor volume was statistically associated with prelaminar optic nerve invasion (P = .001) and choroidal invasion (P = .031). CONCLUSION: MR imaging is accurate for tumor staging and detection of metastatic risk factors; detection of intraocular tumor infiltration remains difficult. Tumor volume, measured with MR imaging, was associated with prelaminar optic nerve and choroidal involvement.

Child↗

PubMed2005

Prognostic factors for duration of sick leave due to low-back pain in dutch health care professionals.

BACKGROUND: Information on prognostic factors for duration of sick leave due to low-back pain (LBP) is growing. In this prospective cohort study prognostic factors for duration of sick leave and course of disability were identified in a very early stage of sick leave due to LBP in an occupational health care setting. METHODS: A total of 615 workers calling in sick from work due to LBP at an occupational health service (OHS) of one institution completed a questionnaire. Duration of follow-up was 26 weeks. Prognostic factors were identified by means of Cox regression analysis and multiple linear regression analysis, and explained variance was calculated. RESULTS: Median time to first return to work (RTW) was 5 days (Inter Quartile Range (IQR) = 2-12). Median time to lasting return to work (LRTW) was 6 days (IQR = 3-13). The final model for delayed RTW included self-reported expected duration of sick-leave, treatment by GP or specialist, care-seeking, diminished mobility, and the interaction between care-seeking and diminished mobility. The final model for LRTW included: self-reported expected duration of sick-leave, treatment by GP or specialist, care-seeking, the interaction between the self-reported expected duration of sick-leave and seeking care at OHS, complaints due to job stress, diminished mobility, and the interactions between expected duration of more then 10 days and seeking OP care and diminished mobility. Median total days on sick leave (TDSL) was 6 days (IQR = 3-13 days). The final model for TDSL included: age, expected duration of sick leave, treatment by GP or medical specialist, seeking OP care, complaints due to physical load, and diminished mobility. Explained variance (R2) of these models ranged from 30 to 35%. CONCLUSIONS: Poor prognosis for duration of sick leave can be identified by means of a simple questionnaire administered on the first day of sick leave. Workers at high risk for longer duration of sick leave (all outcomes) expected to stay off work longer, were already being treated by a MD, sought OP care, and had diminished mobility. In case of delayed LRTW workers reported job stress as a possible cause of sick leave. Interactions were found in both RTW and LRTW between care-seeking and diminished mobility and in LRTW between expected duration of sick leave and seeking OP care. Older age increased TDSL with borderline significance.

Adult↗

PubMed2005

Differential item functioning of the Functional Independence Measure in higher performing neurological patients.

OBJECTIVE: When comparing outcomes of the Functional Independence Measure (FIM ) between patient groups, item characteristics of the FIM should be consistent across groups. The purpose of this study was to compare item difficulty of the FIM in 3 patient groups with neurological disorders. SUBJECTS: Patients with stroke (n=295), multiple sclerosis (n=150), and traumatic brain injury (n=88). METHODS: FIM scores were administered in each group. The FIM consists of a motor domain (13 items) and a cognitive domain (5 items). Rasch rating scale analysis was performed to investigate differences in item difficulty (differential item functioning) between groups. RESULTS: Answering categories of the FIM items were reduced to 3 (from the original 7) because of disordered thresholds and low answering frequencies. Two items of the motor domain ("bladder" and "bowel") did not fit the Rasch model. For 7 out of the 11 fitting motor items, item difficulties were different between groups (i.e. showed differential item functioning). All cognitive items fitted the Rasch model, and 4 out of 5 cognitive items showed differential item functioning. CONCLUSION: Differential item functioning is present in several items of both the motor and cognitive domain of the FIM. Adjustments for differential item functioning may be required when FIMdata will be compared between groups or will be used in a pooled data analysis.

Activities of Daily Living↗

PubMed2005

Implementation of clinical guidelines on physical therapy for patients with low back pain: randomized trial comparing patient outcomes after a standard and active implementation strategy.

BACKGROUND AND PURPOSE: An active strategy was developed for the implementation of the clinical guidelines on physical therapy for patients with low back pain. The effect of this strategy on patients' physical functioning, coping strategy, and beliefs regarding their low back pain was studied. SUBJECTS: One hundred thirteen primary care physical therapists treated a total of 500 patients. METHODS: The physical therapists were randomly assigned to 1 of 2 groups. The control group received the guidelines by mail (standard passive method of dissemination). The intervention group, in contrast, received an additional active training strategy consisting of 2 sessions with education, group discussion, role playing, feedback, and reminders. Patients with low back pain, treated by the participating therapists, completed questionnaires on physical functioning, pain, sick leave, coping, and beliefs. RESULTS: Physical functioning and pain in the 2 groups improved substantially in the first 12 weeks. Multilevel longitudinal analysis showed no differences between the 2 groups on any outcome measure during follow-up. DISCUSSION AND CONCLUSION: The authors found no additional benefit to applying an active strategy to implement the physical therapy guidelines for patients with low back pain. Active implementation strategies are not recommended if patient outcomes are to be improved.

Education, Continuing↗

PubMed2004

Infratentorial lesions predict long-term disability in patients with initial findings suggestive of multiple sclerosis.

BACKGROUND: The number and volume of abnormalities on baseline brain magnetic resonance images in patients with initial findings suggestive of multiple sclerosis are known to predict outcome in terms of disability. However, no long-term data exist on specific locations or types of lesions. OBJECTIVE: To assess the long-term predictive value of baseline magnetic resonance imaging parameters, including location of lesions and gadolinium-enhancing and hypointense lesions in patients with initial findings suggestive of multiple sclerosis for the occurrence of clinically relevant disability as defined by an Expanded Disability Status Scale score of 3. PATIENTS: After a median follow-up period of 8.7 years, the medical records of 42 patients were reviewed and assessed for time until patients received an Expanded Disability Status Scale score of 3. Magnetic resonance imaging parameters were dichotomized according to maximum accuracy and then used to calculate hazard ratios using the Cox model for proportional hazard ratios. RESULTS: Conversion to clinically definite multiple sclerosis was observed in 26 patients (62%), of whom 14 (54%) progressed to an Expanded Disability Status Scale score of 3. Two or more infratentorial lesions best predicted long-term disability (hazard ratio, 6.3). Gadolinium-enhancing and hypointense T1-weighted lesions did not show prognostic value. CONCLUSION: Infratentorial lesions are related to long-term prognosis for patients with initial findings suggestive of multiple sclerosis and thus may help to identify patients at high risk for earlier occurrence of clinically relevant disability.

Adolescent↗

PubMed2004

24-item Roland-Morris Disability Questionnaire was preferred out of six functional status questionnaires for post-lumbar disc surgery.

OBJECTIVE: Measurement properties of questionnaires should be based on samples of populations on whom these measurements will be used. The purpose of this study is to establish an evidence based recommendation regarding the use of functional status questionnaires in patients following a lumbar disc surgery by a direct comparison of the reproducibility and responsiveness. STUDY DESIGN AND SETTING: The measurement properties of six functional status questionnaires were assessed: 1) Roland-Morris Disability Questionnaire (RDQ-24), 2) Modified Roland-Morris Disability Questionnaire (MRDQ), 3) short Roland-Morris Disability Questionnaire (RM-18), 4) Physical Functioning scale, 5) Role Limitations-Physical scale of the SF-36, and 6) The Main Complaint (MC). Subjects (n=97) that still suffered residual complaints 6 weeks following a lumbar disc surgery completed the questionnaires before and 3 months after treatment. In a direct comparison the A) The test-retest reproducibility (Intraclass Correlation Coefficients [ICC] and the Standard Error of Measurement [SEM]) and B) 3 parameters of responsiveness (Minimal Detectable Change [MDC], Standardised Response Mean [SRM], and the Area Under the receiver operator characteristic Curve [AUC]) were assessed. RESULTS: This study suggests the superiority of the 3 versions of the RDQ compared to the 3 other questionnaires. Comparing the 3 versions of the RDQ reveals no substantial differences thereby indicating that the 2 modified version of the RDQ hold no better measurement properties in this specific population. CONCLUSION: The use of the RDQ-24 for this specific post-surgery population is suggested. The optimal cut-off point of the RDQ-24 that minimizes the overall classification error was found to be 3.5 with a sensitivity of 94.6% and a specificity of 88.2%.

Activities of Daily Living↗

PubMed2004

Monocyte activation and disease activity in multiple sclerosis. A longitudinal analysis of serum MRP8/14 levels.

In active multiple sclerosis (MS) lesions macrophages expressing myeloid related protein (MRP) 8/14 are present. The aim of this study was to determine whether serum levels of MRP8/14 complexes are related to disease activity in MS. In a longitudinal study of 16 relapsing remitting (RR) MS patients that underwent monthly gadolinium diethylentriaminepenta acid (Gd-DTPA) magnetic resonance imaging (MRI), the relation between serum MRP8/14 levels and disease activity was investigated. Patients were participating in a monoclonal antibody study targeting a specific T cell population (Vbeta5.2/5.3+ T-cells). In time, within patients large variations in serum MRP8/14 levels were observed. Serum MRP8/14 levels were not related to changes in clinical disease activity or increase in Gd-DTPA lesion enhancement. Neither did comparison of active (>1 relapse in follow-up period) with inactive (0-1 relapse) MS patients reveal any differences in MRP8/14 levels. Therefore, we conclude that although MRP8/14 expression is a good histopathological marker for monocyte activation, serum levels of these proteins do not correlate with disease activity in RR MS.

Adult↗

PubMed2004

Challenging the cholinergic system in mild cognitive impairment: a pharmacological fMRI study.

Mild cognitive impairment (MCI) often represents an early form of Alzheimer disease (AD). In both MCI and AD, characteristic cholinergic changes may occur. Functional magnetic resonance imaging (fMRI) may help to examine neurochemical changes in early disease by studying signal reactivity to pharmacological challenge. In this study, MCI patients [n=28; mean age 73.6+/-7.5; mini mental state examination (MMSE) 27.0+/-1.2] were scanned during task performance in a randomized trial under three different medication regimes: at baseline [BL; no galantamine (GAL)], after a single oral dose of GAL (SD), and after prolonged exposure (steady state: SS). Memory tasks included an episodic face-encoding task and a parametric n-letter back working memory (WM) task. Alterations in brain activation patterns before and after treatment were analyzed for both tasks using multilevel statistical analysis. Significant increases in brain activation from BL were observed after prolonged exposure only. For face encoding (n=28), these involved left prefrontal areas, the anterior cingulate gyrus, left occipital areas, and left posterior hippocampus. For working memory (n=28), increased activation was found in right precuneus and right middle frontal gyrus, coinciding with increased accuracy scores after GAL treatment. In conclusion, cholinergic challenge produces alterations in brain activation patterns in elderly MCI patients that can be detected with fMRI. This should encourage further functional imaging studies to examine the status of neurotransmitter systems in disease.

Administration, Oral↗

PubMed2004

Supraglottic carcinoma treated with curative radiation therapy: identification of prognostic groups with MR imaging.

PURPOSE: To retrospectively assess the prognostic meaning of tumor characteristics depicted on pretreatment magnetic resonance (MR) images for local outcome in supraglottic squamous cell carcinoma treated with definitive radiation therapy. MATERIALS AND METHODS: Pretreatment MR images acquired in 84 patients with supraglottic carcinoma treated with curative radiation therapy were reviewed for tumor involvement of laryngeal sites including glottis, subglottis, pre-epiglottic space, laryngeal cartilages, and hypopharynx, and for extralaryngeal extension. The volume of each tumor was estimated, and mean tumor volume was calculated for the group of tumors in each T staging category. RESULTS: Results of univariate analysis showed MR imaging-determined primary tumor volume (P =.03), involvement of pre-epiglottic space (P =.008), abnormal signal intensity in thyroid cartilage (P =.04), and extralaryngeal extension beyond thyroid and/or cricoid cartilage (P =.02) to be significant predictors of local control rate. Results of multivariate analysis with the Cox regression model confirmed statistical significance for invasion of pre-epiglottic space (P =.004) and for abnormal signal intensities in thyroid cartilage adjacent to the anterior commissure (P =.04) and in cricoid cartilage (P =.01). Five-year local control rates were calculated from the regression coefficients of three independent MR imaging prognostic factors, and three prognostic groups were identified on the basis of these control rates. The 5-year local control rate in the high-risk group was 35%, significantly lower than the rates in the intermediate- and low-risk groups (60% and 89%, respectively; P =.002). CONCLUSION: MR imaging-determined pre-epiglottic space involvement and abnormal signal intensities in the thyroid cartilage adjacent to the anterior commissure and/or the cricoid cartilage are strong predictors of local outcome in supraglottic carcinoma treated with definitive radiation therapy.

Adult↗

PubMed2003

Operational definitions for the NINDS-AIREN criteria for vascular dementia: an interobserver study.

BACKGROUND AND PURPOSE: Vascular dementia (VaD) is thought to be the most common cause of dementia after Alzheimer's disease. The commonly used International Workshop of the National Institute of Neurological Disorders and Stroke (NINDS) and the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (AIREN) criteria for VaD necessitate evidence of vascular disease on CT or MRI of the brain. The purposes of our study were to operationalize the radiological part of the NINDS-AIREN criteria and to assess the effect of this operationalization on interobserver agreement. METHODS: Six experienced and 4 inexperienced observers rated a set of 40 MRI studies of patients with clinically suspected VaD twice using the NINDS-AIREN set of radiological criteria. After the first reading session, operational definitions were conceived, which were subsequently used in the second reading session. Interobserver reproducibility was measured by Cohen's kappa. RESULTS: Overall agreement at the first reading session was poor (kappa=0.29) and improved slightly after application of the additional definitions (kappa=0.38). Raters in the experienced group improved their agreement from almost moderate (kappa=0.39) to good (0.62). The inexperienced group started out with poor agreement (kappa=0.17) and did not improve (kappa=0.18). The experienced group improved in both the large- and small-vessel categories, whereas the inexperienced group improved generally in the extensive white matter hyperintensities categories. CONCLUSIONS: Considerable interobserver variability exists for the assessment of the radiological part of the NINDS-AIREN criteria. Use of operational definitions improves agreement but only for already experienced observers.

Brain↗

PubMed2003

The interleukin-1 gene family in multiple sclerosis susceptibility and disease course.

Multiple sclerosis (MS) is a chronic disease of presumed autoimmune origin with a considerable polygenic influence. We have previously observed that a specific allele combination in genes of the interleukin-1 (IL-1) family influenced the progression rate in MS. We have considerably expanded our patient population (492 MS patients and 228 controls). In the present study, we investigated the role of the IL-IA--889, IL-1B--511, IL-1B f3953 and IL-1RN VNTR gene polymorphisms in MS. In addition, we performed preliminary analyses on longitudinal magnetic resonance imaging (MRI) data. We found no associations between the polymorphisms and susceptibility to MS or clinical features. In addition, we observed no significant effect of the polymorphisms on brain or lesion volumes, Based on our data and those from the literature, one can conclude that there is currently no evidence to support a role for the IL-1 genes in MS.

Adult↗