Biomedical subjects

Cornelis J Biesheuvel

Publications and source records attributed to Cornelis J Biesheuvel.

4 recordsLinked to original sources

PubMed2006

Distraction from randomization in diagnostic research.

The ultimate goal of medical care, including diagnostic testing, is to improve patient outcome. Accordingly, it has been advocated widely that when establishing a test's diagnostic accuracy, the impact of the test on patient outcome subsequently must be quantified. When studying patient outcome in medical research, the use of randomized comparisons comes into perspective. In our view, randomized studies often are not necessary to validly estimate the effect of the diagnostic test on patient outcome. Results of cross-sectional diagnostic studies, combined with results from therapeutic studies, often will suffice.

Cross-Sectional Studies↗

PubMed2006

Validating and updating a prediction rule for neurological sequelae after childhood bacterial meningitis.

Recently, a prediction rule for developing neurological sequelae after childhood bacterial meningitis was developed on a small derivation set. Before implementing in practice a prediction rule must first be tested in new patients (external validation). Our aim was to study the external validity of this rule and, if necessary, to update the rule. The prediction rule was tested on newly available data (validation set) by assessing the rule's calibration and discrimination. We updated the prediction rule by adding extra predictors and re-estimating the regression coefficients of the original predictors in the combined datasets. The rule showed poor agreement between predicted risks and observed frequencies. The ROC area was 0.65 (95% CI 0.57-0.72), which was statistically significantly lower than in the derivation set (0.87 (0.78-0.96)), p-value<0.01. The updated prediction rule showed adequate performance in the combined data sets; the ROC area was 0.77 (95% CI 0.72-0.82). Further study of the generalizability of this updated rule may stimulate application in clinical practice.

Child↗

PubMed2004

Genetic programming outperformed multivariable logistic regression in diagnosing pulmonary embolism.

OBJECTIVE: Genetic programming is a search method that can be used to solve complex associations between large numbers of variables. It has been used, for example, for myoelectrical signal recognition, but its value for medical prediction as in diagnostic and prognostic settings, has not been documented. STUDY DESIGN AND SETTING: We compared genetic programming and the commonly used logistic regression technique in the development of a prediction model using empirical data from a study on diagnosis of pulmonary embolism. Using part (67%) of the data, we developed and internally validated (using bootstrapping techniques) a diagnostic prediction model by genetic programming and by logistic regression, and compared both on their predictive ability in the remaining data (validation set). RESULTS: In the validation set, the area under the ROC curve of the genetic programming model was significantly larger (0.73; 95%CI: 0.64-0.82) than that of the logistic regression model (0.68; 0.59-0.77). The calibration of both models was similar, indicating a similar amount of overoptimism. CONCLUSION: Although the interpretation of a genetic programming model is less intuitive and this is the first empirical study quantifying its value for medical prediction, genetic programming seems a promising technique to develop prediction rules for diagnostic and prognostic purposes.

Adult↗

PubMed2004

Walking exercise in patients with intermittent claudication. Experience in routine clinical practice.

BACKGROUND: In patients with intermittent claudication, exercise in the form of walking is effective in reducing pain and maximising achievable walking distance. However, data are lacking on the implementation of walking exercise in these patients. AIMS: To explore the current behaviour and views of patients with intermittent claudication towards taking walking exercise. DESIGN OF STUDY: Postal questionnaire and focus group meetings. SETTING: Two academic general practice networks (Utrecht and Maastricht Universities) in The Netherlands. METHOD: Three hundred and seventy-five patients with intermittent claudication, selected from the files of general practitioners participating in two academic general practice networks, were sent a postal questionnaire; 216 (58%) were returned. Nine of these responders also attended a focus group meeting. RESULTS: Seventy per cent (151/216) of the patients reported having received advice about walking exercise. If specified, the advice given most often recommended walking in the local neighbourhood (56%, 84/151). Fifty-two per cent (113/216) of all patients actually performed walking exercise and only 32%of them received any kind of supervision. Among the barriers for taking walking exercise, 'comorbidity', 'lack of (specific) advice' and 'lack of supervision' were often mentioned. Among the stimuli to start and continue walking, 'following the doctor's advice', 'relief of complaints' and 'a better general condition' were often mentioned by patients. CONCLUSIONS: Walking exercise was not carried out by almost half of patients with intermittent claudication in this study. Lack of specific advice and supervision were found to be important barriers to taking walking exercise.

Adult↗