Maternal haemoglobin and pregnancy outcome.
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Female↗
Biomedical subjects
J A Knottnerus
Publications and source records attributed to J A Knottnerus.
[Unexplained fatigue and hemoglobin level; a study of family practice patients].
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Adolescent↗
Interpretation of diagnostic data: an unexplored field in general practice.
In interpreting diagnostic information the differences between morbidity patterns in general practice and those in hospitals must be taken into consideration. This article demonstrates the importance of prevalence for predictive values of complaints, symptoms and test results. When the general practitioner refers patients to the specialist, these values may change, and it is also possible that associations between symptoms and diagnoses are distorted by selection bias. Moreover, attention must be paid to the differences in clinical stages encountered in general practice and specialist practice. It is concluded that a large part of the ;diagnostic field' of general practice has still to be discovered and developed.
Breast Neoplasms↗
General practice registration networks in the Netherlands: a brief report.
In the Netherlands, several general practice registrations exist. Groups of general practitioners register elements of patient care according to agreed-upon criteria, and these data are collected in a central database. By means of a questionnaire the authors interviewed the managers of all nine computerized registration networks extensively about the possibilities and limitations of their registration. In addition, respondents answered some questions with data from the central database of their network. Various items are collected by nearly all the registration networks, while other items are collected by only one network. Answering questions with data from the central database turned out to be difficult. Organization and manpower are the main obstacles.
Databases, Factual↗
Effect of oral anticoagulant treatment on markers for calcium and bone metabolism.
Vitamin K-dependent proteins regulate blood coagulation as well as bone growth and calcification. Here, we have compared the effects of oral anticoagulants on circulating vitamin K-dependent proteins and on markers for calcium and bone metabolism. Patients with a clinical indication for antithrombotic therapy were randomized into three groups and treated with either aspirin, regular-intensity anticoagulation [target international normalized ratio (INR) values: 2.5-3.5] or low-intensity anticoagulation (target INR values: 1.1-1.6). At the start and after 1 year of treatment, various biochemical markers were assessed. Both the circulating levels and the degree of carboxylation of the various gamma-carboxyglutamate (Gla)-containing proteins were affected differently by oral anticoagulant treatment. Circulating osteocalcin was more sensitive to poor vitamin K status than other Gla proteins. From the fact that - except for osteocalcin - neither markers for osteoblast nor osteoclast function were affected by oral anticoagulant treatment, we conclude that bone turnover remained unaltered, which is indicative of an unchanged rate of bone loss. Whether the long-term production of undercarboxylated bone Gla proteins may have a negative effect on the quality of bone (e.g. bone strength) cannot be concluded from this study.
Administration, Oral↗
The effects of disease verification and referral on the relationship between symptoms and diseases.
Reference symptoms of individual diseases, which are usually gleaned from hospital-based observations, may not be pertinent to primary health care. Observed relationships between symptoms and diseases can be biased by consultation, disease verification, and referral patterns. These biases are shown to affect sensitivity, specificity, predictive values, the likelihood ratio, and the odds ratio. On the assumption that consultation and disease verification rates are positively influenced by symptoms, but not directly by the yet unknown disease status of the patient, the general practitioner will observe a higher sensitivity and a lower specificity than in an unselected population. A positive correlation between symptom and disease will decrease the likelihood ratio, while the predictive values and the odds ratio are not changed after consultation. Referral is influenced by both symptom status and disease verification status. In general, the disease verification and referral patterns of general practitioners have not been quantified. While the influence of referral cannot easily be corrected for, the likely magnitude and direction of selection bias can be evaluated using simple formulas. A possible way to make unbiased estimations from populations preselected by referral is to compute the predictive values and the odds ratio from the category of patients referred without pre-existing knowledge of the disease status.
Diagnosis↗
Application of logistic regression to the analysis of diagnostic data: exact modeling of a probability tree of multiple binary variables.
In the analysis and presentation of diagnostic relationships by means of conventional multiple logistic regression, the following limitations occur: 1) the model starts not from the prior disease odds but from the posterior disease odds for all test variables having a zero value; 2) apart from the odds ratio, other test characteristics cannot be read from the model; 3) the sequence of entering of terms is guided by pure statistical criteria and not primarily by the criterion gain in certainty; 4) interactions are not very comprehensibly represented and are difficult to interpret. A method dealing with these limitations with respect to the analysis of data on the relationships between binary tests and disease outcome is described. Essential is the transformation of any test variable x to (x - x0), where x0 is that specific (virtual) value of x so that: posterior disease odds = prior disease odds, and consequently LRx0 = 1. Moreover, a simple branching structure is introduced while the terms are entered in order of decreasing gain in certainty. Examples are given for one-, two-, and three-test situations with and without dependency and interaction of tests, and general formulas are presented. For situations with the same prior probability, and the same overall discrimination of the separate test variables, all equations clearly have a common basis. Inclusion of new variables does not affect coefficients previously included in the model, and terms without a significant contribution can be skipped without affecting other coefficients. Standard errors and confidence intervals of test characteristics can be computed using the BMDP LR program. Further study needs to be done on the inclusion of continuous variables and cost-benefit aspects, and comparison with the performance of the CART program.
Bayes Theorem↗
The diagnostic value of scoring models for organic and non-organic gastrointestinal disease, including the irritable-bowel syndrome.
Scoring models based on history and physical examination have been developed to discriminate patients with non-organic gastrointestinal disease from those who have organic disease. The application of these models may lead to more efficient diagnosis and prevent somatization. Although the models have high diagnostic accuracy in the population in which they have been developed, their value in other populations has not been established. In this study previously developed models were tested in validation populations defined by the original selection criteria from the studies in which the models were developed and in unselected general practice and outpatient populations. The diagnostic performance of the models are expressed in terms of odds ratio and sensitivity and specificity for the classification of patients as having organic and non-organic disease. The diagnostic performance of all the models were rather low in the validation populations. Relatively few elements of the models had independent diagnostic value. In addition, the correlation between the scoring models, expressed in Cohen's kappa, was extremely low. The diagnostic values of the scoring models were not reproduced in comparable and unselected populations. Therefore, it is concluded that the diagnostic value of such a model has little external validity.
Adolescent↗
Routine individual feedback on requests for diagnostic tests: an economic evaluation.
The authors assessed the economic cor sequences of routine individual feedback on test requests provided to 85 family physicians in a region with 187,000 inhabitants. In a retrospective study as part of a quasi-experiment, cost trends in a region where feedback was provided over a seven-year period were compared with cost trends elsewhere in The Netherlands without feedback. Data on variable costs were obtained for 400 individual tests that accounted for 90% of all requests. Differences in request trends thus were transformed to savings in costs of diagnostic testing, taking account of the extra costs of providing the feedback. Expenditures for diagnostic testing declined after the start of the feedback, despite the costs of providing the feedback. The savings increased as the feedback continued. Compared with the trend elsewhere without feedback, over seven years a total net sum of 1.4 million U.S. dollars was saved. Routine individual feedback is therefore economically worthwhile.
Clinical Laboratory Techniques↗
Diagnostic value of signs and symptoms associated with peripheral arterial occlusive disease seen in general practice: a multivariable approach.
OBJECTIVES: To assess the diagnostic values of single and combined data from the history, physical examination, and medical record with regard to peripheral arterial occlusive disease (PAOD) in patients with leg complaints; to construct a multivariable model for the clinical diagnosis of PAOD by primary care physicians. SETTING: 18 general practice centers in The Netherlands. DESIGN: Cross-sectional comparison of signs, symptoms, and data from the medical record with the independently assessed ankle-brachial systolic pressure index (ABPI; cutoff point < 0.90); analysis: bivariate, multiple logistic regression (MLR). POPULATION: 2,455 individuals with leg complaints, aged 40.7-78.4 years; ABPI < 0.90 present in 9.2% of legs (11.7% of individuals). OUTCOME MEASURES: Clinical variables: sensitivity, specificity, positive and negative predictive values (PV+, PV-), diagnostic odds ratio (OR); models: likelihood ratio test, area under the receiver operating characteristic curve (AUC). RESULTS: Bivariate analysis: highest sensitivity: age more than 60 years (77.3%); highest specificity: wounds or sores on toes and foot (99.7%); highest PV+: typical intermittent claudication (IC) (45.0%) (abnormal foot pulses 41.3%); highest PV-: strong pulses of both foot arteries (97.7%). MRL: the best-performing model (AUC 0.89) consisted of ten clinical variables: gender (OR 1.5), age more than 60 (OR 2.2); IC (OR 3.5); palpation of the skin temperature of the feet (OR 2.5), palpation of both foot pulses [OR 16.4 (abnormal) and 7.0 (doubtful)], auscultation of the femoral artery (OR 3.5); previous diagnosis of IHD (OR 1.7) or diabetes (OR 1.6), history of smoking (OR 2.1), and elevated blood pressure (OR 1.5). The range of predicted probabilities was 0.4-98%. The Hosmer-Lemeshow goodness-of-fit test indicated good overall fit (p = 52). CONCLUSIONS: Palpation of both foot pulses is the key procedure for the clinical diagnosis of PAOD. Traditional clinical evaluation enables the general practitioner to exclude the diagnosis of PAOD in many individuals with a high degree of certainly, to establish the diagnosis in a small group of patients, and to define a limited group of patients where supplementary noninvasive testing is appropriate. The MLR model can be used as a diagnostic checklist and as a reference for the physician's clinical hypothesis.
Adult↗
Multiattribute utility scores for predicting family physicians' decisions regarding sinusitis.
To examine whether multiattribute utility (MAU) scores can be used to predict family physicians' decisions regarding patients suspected to have sinusitis and rhinitis, 100 randomly selected family physicians from the Leiden area (The Netherlands) were asked to rank a set of six attributes regarding their importance, yielding attribute weights. Next, the physicians were asked to rate the degrees to which five decision alternatives optimized each attribute, yielding utilities, regarding three case vignettes about a patient suspected to have acute maxillary sinusitis and rhinitis, with a brief clinical history. By combining attribute weights and utilities, a MAU score was calculated for each decision alternative regarding each case vignette. Finally, for each case vignette the physicians' treatment preferences were assessed by means of an open-ended question. For the clear-cut sinusitis case, management strategies and highest MAU scores were concordant for 80% of the physicians. Regarding the dubious sinusitis and rhinitis case, concordance was 50%. The latter was associated with small differences in values between the highest MAU scores. Because agreement among the physicians regarding the management strategies and weight ranks was high and there was little variation in the highest MAU scores, the kappas between the reported management strategies and weight ranks were poor (0.24 and lower). It is concluded that MAU scores may be used to predict family physicians' decisions regarding the management of patients suspected of having sinusitis where there are significant differences in values between the highest MAU scores.
Adult↗
Comparison of Cytobrush sampling, spatula sampling and combined Cytobrush-spatula sampling of the uterine cervix.
Since the introduction of the Cytobrush for sampling the uterine cervix, some practitioners have ceased taking a concomitant cervical scraping using a spatula. To examine whether Cytobrush sampling alone is adequate for the diagnosis of cervical lesions, the Cytobrush and spatula samples in 444 smears (most with original diagnoses of at least mild dysplasia) were analyzed separately for the presence of diagnostic cells, endocervical cells and squamous cells. Of the 412 smears showing pathologic findings (mild to severe dysplasia or worse), diagnostic cells were present in 400 Cytobrush samples and in 369 spatula samples; the combination of both samples thus gave a 3% gain in correct diagnoses as compared to use of the Cytobrush samples alone. Another 18 smears would have been underdiagnosed based only on the Cytobrush samples. Endocervical cells were present in 95.3% of the Cytobrush samples and 83.8% of the spatula samples; squamous cells were present in 93.9% of the Cytobrush samples and 96.8% of the spatula samples. Analysis confirmed that it is important that the smear should contain both endocervical and squamous cells. A positive relationship between the absence of squamous cells in the Cytobrush sample and the probability of a false-negative assessment was suggested. It thus seems inadvisable to replace the combination sampling method by Cytobrush sampling alone, which may lead to a false-negative diagnosis.
Adult↗