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J A Knottnerus

Publications and source records attributed to J A Knottnerus.

At least 127 records · Page 7Linked to original sources
PubMed1995

Diagnostic prediction rules: principles, requirements and pitfalls.

This article focuses on the background, principles, requirements, and pitfalls of diagnostic prediction rules. Useful rules can only be derived from methodologically valid data bases. By considering the possibilities and limitations of prediction rules, the author concludes that these rules may support medical decision making, but cannot be a substitute for clinical skills and solid pathophysiologic knowledge.

Decision Support Techniques↗
PubMed1995

Does a reduction in general practitioners' use of diagnostic tests lead to more hospital referrals?

BACKGROUND: Individual feedback on general practitioners' requests for tests can improve the quality of their test ordering behaviour. Little is known of the side effects on hospital referral behaviour when the use of tests is reduced through feedback. AIM: A study was undertaken to explore changes in general practitioners' hospital referral rates in a region where their use of diagnostic tests is reduced through feedback. METHOD: Trends in test requests and of first referrals to specialists were compared among 64 general practitioners in the Maastricht region of the Netherlands where routine feedback on test ordering behaviour is provided by the diagnostic coordinating centre. RESULTS: Reduction in diagnostic test use was not accompanied by a higher hospital referral rate, not even for specialties related to tests discussed in feedback. Good responders to feedback had decreased hospital referral rates in contrast to increased rates for poor responders (P < 0.01). CONCLUSION: Reducing the volume of general practitioners' diagnostic tests through feedback does not lead to more specialist referrals. Together with lower test use, fewer hospital referrals were seen.

Diagnostic Tests, Routine↗
PubMed1995

Non-acute abdominal complaints in general practice: diagnostic value of signs and symptoms.

BACKGROUND: Although many patients are evaluated initially by their general practitioner, clinicians' accuracy at diagnosing organic gastrointestinal disease has not been studied in a primary care setting. Different spectra of severity of disease in general practice and hospital populations may lead to different values for diagnostic tests in these two populations. AIM: This study set out to determine the diagnostic value of history and physical and laboratory items for organic and neoplastic disease in general practice patients with nonacute abdominal complaints. METHOD: The one-year prospective, observational study was carried out in 1989 in 80 general practices in Limburg, the Netherlands. The study subjects were 933 patients (aged 18-75 years) presenting to their general practitioner with new non-acute abdominal complaints of minimum duration two weeks, and with whom the doctor had a diagnostic problem. Patients were physically examined by their general practitioner and asked to complete pre-structured questionnaires. Basic laboratory tests were carried out. Patients were followed up for at least one year by researchers and then a diagnosis was determined by an independent panel of three general practitioners using patient records, blinded for the results of the questionnaires. Sensitivity, specificity and odds ratios were calculated for clinical items. Stepwise forward logistic regression analysis was undertaken to identify independent predictors of organic gastrointestinal disease. RESULTS: Of the 933 patients 14% had organic gastrointestinal disease. No clinical item had both high sensitivity and specificity. Logistic regression analysis showed only eight independent predictors of organic disease: male sex, greater age, epigastric pain, no specific character to pain, pain affecting sleep, history of blood in stool, no pain relief after defecation and abnormal white blood cell count. When the model was programmed to predict neoplasms five items were found: male sex, greater age, no specific character to pain, weight loss and erythrocyte sedimentation rate greater than 20 mm hour-1. CONCLUSION: In a general practice population with non-acute abdominal complaints some clinical findings can be used as predictors for organic and neoplastic gastrointestinal disease.

Adolescent↗
PubMed1995

The medical profile of unidentified problem drinkers in general practice: test of an hypothesis.

In order to facilitate general practitioner (GP) detection of problem drinkers the Dutch College of General Practitioners developed a standard specifying the differences in medical profile between problem drinker and non-problem drinkers. The standard mentions 35 Reasons for Encounter (RFEs) and GP Evaluations (Es) that are thought to be specific for problem drinkers. The studies referred to in the standard base their conclusions about differences in medical profile upon a comparison of problem drinkers already identified by the GP with other patients. This study tests the hypothesis that the medical profile specified by the standard also applies to unidentified problem drinkers. All known problem drinkers in the practices of 16 GPs, as well as a one in 10 random sample of patients considered to be non-drinkers were admitted to the study at their first surgery visit during a 1-year period. Hidden problem drinkers were detected by means of a screening questionnaire, although the results were not conveyed to the GP until the study was completed. Over the 1-year study period the GPs then registered all RFEs and Es of the study population. RFE and E sum scores were then constructed based on the Alcohol Standard. The estimated population prevalence of problem drinking, corrected for the one in 10 sample fraction was 7%. We found 6% problem drinkers (n = 78) in the category regarded by the GPs as non-problem drinkers (n = 1254). Differences in RFEs and Es between hidden problem drinkers and those regarded as non-problem drinkers were significant for irregular heartbeat and psychological problems. Sexual problems were significant at the RFE level, social problems at the E level. When identified problem drinkers are compared with non-problem drinkers more differences in the medical profile are found (four times both RFE and E; twice RFE and once E). We conclude that most of the published differences in the medical profile between problem drinkers and other GP patients are not found for unidentified problem drinkers. The observed differences between unidentified problem drinkers and non-problem drinkers are too small to be helpful to the GP to detect problem drinkers.

Adult↗
PubMed1994

The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial.

OBJECTIVE: To determine the efficacy of influenza vaccination in elderly people. DESIGN: Randomized double-blind placebo-controlled trial. SETTING: Fifteen family practices in the Netherlands during influenza season 1991-1992. PARTICIPANTS: A total of 1838 subjects aged 60 years or older, not known as belonging to those high-risk groups in which vaccination was previously given. INTERVENTION: Purified split-virion vaccine containing A/Singapore/6/86(H1N1), A/Beijing/353/89(H3N2), B/Beijing/1/87, and B/Panama/45/90 (n = 927) or intramuscular placebo containing physiological saline solution (n = 911). MAIN OUTCOME MEASURES: Patients presenting with influenzalike illness up to 5 months after vaccination; self-reported influenza in postal questionnaires 10 weeks and 5 months after vaccination; serological influenza (fourfold increase of antibody titer between 3 weeks and 5 months after vaccination). RESULTS: The incidence of serological influenza was 4% in the vaccine group and 9% in the placebo group (relative risk [RR], 0.50; 95% confidence interval [CI], 0.35 to 0.61). The incidences of clinical influenza were 2% and 3%, respectively (RR, 0.53; 95% CI, 0.39 to 0.73). The effect was strongest for the combination of serological and clinical influenza (RR, 0.42; 95% CI, 0.23 to 0.74). The effect was less pronounced for self-reported influenza. CONCLUSION: In the elderly, influenza vaccination may halve the incidence of serological and clinical influenza (in periods of antigenic drift).

Aged↗
PubMed1994

Short term effect of withdrawal of diuretic drugs prescribed for ankle oedema.

OBJECTIVE: To determine the effect of withdrawing diuretic drugs on oedema in patients prescribed them for only ankle oedema, excluding patients with cardiac, hepatic, or renal failure. DESIGN: Randomised controlled trial. SETTING: 15 general practices in the Netherlands. PATIENTS: 1202 patients aged 65 years or older and taking diuretic drugs, 63 of whom were eligible for the trial. MAIN OUTCOME MEASURE: Change in volumetrically determined ankle oedema (oedema index) over six weeks. RESULTS: 34 patients were randomised to stop diuretics and 29 to the control group. In eight patients diuretics had to be restarted. Among patients who had diuretics withdrawn successfully, rebound oedema caused a temporary increase in mean oedema index. The peak level (3.5% (95% confidence interval 1.5% to 5.2%) was reached in the third week, after which the oedema seemed to be returning to the baseline level. CONCLUSION: Few patients who have been prescribed diuretics for only ankle oedema clearly have no contraindications to withdrawing diuretics. If patients are unlikely to have cardiac insufficiency and careful monitoring is provided, withdrawal of diuretics seems to be feasible, though moderate rebound oedema may occur for a short time.

Aged↗
PubMed1994

Immune response to influenza vaccination of elderly people. A randomized double-blind placebo-controlled trial.

The objective of this study was to determine the immune response to influenza vaccination in elderly people, using a randomized, double-blind, placebo-controlled trial. Venous blood was taken from 1838 people aged 60 years and older, prior to injection with the influenza vaccine or a placebo. A second blood sample was taken three weeks later. The antibody reaction was measured by comparing the geometric mean titre and the percentage of participants who had a protective antibody titre before and after vaccination and for all sera of each strain. A protective antibody titre was found in 43-68% of those who had received the vaccine, depending on the strain investigated. Patients potentially at risk showed a response similar to the other participants. We conclude that influenza vaccination in elderly people provides a reasonable to good immune response. Research is needed on whether a good immune response decreases the incidence of influenza.

Aged↗
PubMed1994

Prevalence and detection of micturition problems among 2,734 elderly men.

In previous studies symptom prevalence of micturition problems in the population appeared to be high. Our study supports these data and adds retrospective data on doctor visits, with 25% reporting a doctor visit during the last 5 years for a micturition problem. However, all symptoms (hematuria, dysuria, incontinence and symptoms possibly related to benign prostatic hyperplasia) showed substantial numbers of patients who were not sufficiently motivated or did not have the opportunity to visit a doctor for diagnosis and advice. Multiple logistic regression analysis showed a number of symptoms that independently predict doctor visits for benign prostatic hyperplasia and related diseases (frequent urination at night, frequent urination during the day, incomplete emptying, dysuria and incontinence). We conclude that the iceberg phenomenon applies to the number of patient visits and the predictive value of symptoms for prognosis of several prostate diseases.

Aged↗
PubMed1994

The effect of different sampling devices on the presence of endocervical cells in cervical smears. A systematic literature review.

A literature search examined 39 reports on the relationship between the absence of endocervical cells in a cervical smear and the sampling technique used. Using (pooled) ratios we compared the results for different pairs of sampling devices, thereby controlling for the design of each study when appropriate. The Cytobrush appears the most efficient sampling method with regard to the presence of endocervical cells. Combining the results of this review with the results of a previous meta-analysis on the effect of the sampling technique on the detection of pathology, the combined spatula and Cytobrush technique seems to be the best sampling method.

Cervix Uteri↗
PubMed1994

Occurrence and clinical significance of overt blood loss per rectum in the general population and in medical practice.

While the occurrence of blood loss per rectum in general practice is common and usually not serious, it may be the first symptom of a colorectal malignant disorder. To determine the occurrence and clinical significance of overt blood loss per rectum a Medline literature search was undertaken. The incidence of this symptom in the general population was reported to be approximately 20 per 100 people per year, the 'consultation incidence' in general practice approximately six per 1000 and the incidence of referral to a medical specialist was estimated to be about seven per 10,000 per year. The clinical significance of the symptom varied within different populations: the predictive value of overt rectal blood loss for colorectal malignancy was estimated to be less than one in 1000 in the general population, approximately two in 100 in general practice and up to 36 in 100 in referred patients. How the manifestation of the bleeding (and other signs and symptoms) contributes to the selection of patients at each of these stages, leading to increasing prior probabilities, is unknown.

Adult↗
PubMed1994

Discriminant value of symptoms in patients with dyspepsia.

BACKGROUND: Family physicians encounter many pitfalls in managing and treating dyspeptic patients, most of whom are treated in family practice based solely on their signs and symptoms. METHODS: A computer literature search followed by a systematic methodological appraisal was performed to identify studies that evaluated clinical symptomatology in dyspeptic patients. RESULTS: Ten studies, none of which took place in a family practice, fulfilled our inclusion criteria. The main conclusion drawn from outpatient populations and patients referred for open-access endoscopy was that certain clusters of symptoms have a negative predictive value for organic causes of dyspepsia. Higher age, male sex, pain at night, relief by antacids or food, and previous history of peptic ulcer disease were identified as predictors of organic causes for abdominal symptoms. CONCLUSIONS: These findings can be helpful to family physicians in determining the need for endoscopy referral. However, since the diagnostic values of tests in family practice may differ from those in referred populations, there is a need for prospective studies in primary care.

Dyspepsia↗
PubMed1993

Adverse reactions to influenza vaccine in elderly people: randomised double blind placebo controlled trial.

OBJECTIVE: To assess the frequency and type of side effects after influenza vaccination in elderly people. DESIGN: Randomised double blind placebo controlled study. SETTING: 15 general practices in the southern Netherlands. SUBJECTS: 1806 patients aged 60 or older, of whom 904 received influenza vaccine and 902 placebo. MAIN OUTCOME MEASURES: Adverse reactions reported on postal questionnaire completed four weeks after vaccination. RESULTS: 210 (23%) patients given vaccine reported one or more adverse reactions compared with 127 (14%) given placebo. The frequency of local adverse reactions were 17.5% in the vaccine group and 7.3% in the placebo group (p < 0.001). There was no difference in systemic adverse reactions (11% v 9.4%; p = 0.34). In general, men reported fewer side effects than women. CONCLUSION: Only local side effects were more common in vaccinated patients and all side effects were mild.

Age Factors↗
PubMed1993

Interobserver variation in the assessment of the sampling quality of cervical smears.

In order to assess the interobserver variation among cytological assistants in evaluating the sampling quality of cervical smears, all four laboratory assistants from one cytological department examined the same set of 71 smears. They assessed the presence of endocervical cells, the quality of fixation, the number of cells and the undesirable presence of clumps of cells. The interobserver agreement, uncorrected for chance, varied from 73 to 93% for the presence of endocervical cells and from 86 to 100% for the three other criteria. For the presence of endocervical cells, the kappa values, a measure for the interobserver agreement corrected for chance, varied from 42 to 84%. This is a reasonable outcome. For the three other criteria many kappa values were zero or uncalculable. The interobserver agreement in evaluating the sampling quality of cervical smears is reasonable to good, but not perfect. Prudence in the interpretation of quality data is warranted.

Female↗
PubMed1993

The diagnostic value of rectal examination.

The rectal examination is a much advocated procedure for assessing abdominal and urinary symptoms. A Medline literature search yielded only a few studies, not one of them in a general practice setting. The sensitivity of the rectal examination to rectal carcinoma and appendicitis is low, while it is high for prostate carcinoma. When reviewing the likelihood ratios of normal and abnormal findings of rectal examinations it was concluded that it may be a useful procedure in the case of abnormal findings in patients presenting rectal problems and in assessing men with prostate problems, although it does not seem useful in diagnosing appendicitis. However, since the diagnostic values in general practice and in referred populations may be different, there is a need for further prospective studies in settings of general medical practice.

Appendicitis↗
PubMed1993

Influencing diagnostic and preventive performance in ambulatory care by feedback and reminders. A review.

The number of good quality studies on the effect of feedback and reminders on diagnostic and preventive activities in ambulant practice is still low. The interventions and procedures studied differ widely, and the reporting of the results is insufficiently precise. This makes comparison difficult and quantitative pooling impossible. Nevertheless, the literature supports the contention that feedback reduces the use of diagnostic tests and the costs thereby engendered. It also discloses a positive effect of feedback on the adherence of medical practice to guidelines or standards. In this respect, the effect of reminders seems to exceed that of classical methods of feedback. There is still a need for research on the effect of feedback, reminders and other instruments for quality assurance on various aspects of medical performance in different settings.

Ambulatory Care↗
PubMed1993

The incidence and outcome of rectal bleeding in general practice.

The objective of the studies reported in this paper was to determine the incidence as well as the final diagnostic outcome of rectal bleeding presenting in general practice. Because of the wide variety observed in incidence rates among 83 general practitioners (GPs) in the first study (A) an additional study (B) was undertaken. In study B with 10 GPs special efforts were made to maximize the catchment rate. The mean 'consultation incidence rate' was 7 per 1000 people per year. A follow-up period of at least 1 year was applied to establish the final diagnostic conclusion. Occurrence of colorectal cancer was found in 3% of patients with rectal bleeding. This may represent an overestimation of the prior probability since there was a selection in favour of patients with clinically relevant rectal bleeding. In about 90% of patients rectal bleeding was related to minor ailments or self-limiting disorders. Further study on predictive values of (combinations of) other signs and symptoms is necessary to develop clinical recommendations.

Adolescent↗
PubMed1993

Abdominal pain in general practice.

Five hundred and seventy-eight consecutive cases of non-acute abdominal pain presenting to 11 general practices were included in a descriptive study and were followed during 15 months. Females predominated in the younger age groups. Eighty per cent of these patients visited their GP not more than three times for abdominal complaints during the follow-up period. Eighty-three per cent were managed entirely in the practice and 64% received a prescription. Only 20% of patients were additionally investigated in any way by the GP. There were hardly any differences in final diagnoses between patients who had complaints less than 1 week or more than 1 week before presenting to the GP. Non-acute abdominal pain is a condition that is seen and managed mainly in general practice.

Abdominal Pain↗