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Biomedical subjects

J D Habbema

Publications and source records attributed to J D Habbema.

At least 19 recordsLinked to original sources
PubMed1992

Predicting mortality from cervical cancer after negative smear test results.

OBJECTIVE: To assess the relative protection against death from cervical cancer after two or more negative smear test results and compare it with the protection against invasive cancer estimated by an International Agency for Research on Cancer (IARC) working group in an analysis of data from 10 large screening programmes. DESIGN: Comparison of risk of death from cervical cancer after two or more negative smear results with the risk in unscreened women by using a model constructed with data from the British Columbia screening programme. MAIN OUTCOME MEASURES: Mortality from and incidence of invasive cancer. RESULTS: In women with two negative smear results estimates of protection against cervical cancer were about 50% higher when lethal invasive cancer was used as the criterion rather than all invasive cancer. This difference was due to these women being more likely to attend for further tests at which invasive cancer could be detected: screen detected cancer has a better prognosis than clinically diagnosed cancer. Screening intervals could be longer than three years: screening women aged 35-64 every five years was predicted to result in a 90% reduction in mortality from cervical cancer. CONCLUSION: Because protection from mortality is higher than protection from disease and because of the high costs and negative side effects of frequent screening, screening intervals should be longer than three years.

Adult↗
PubMed1992

A model for variations in single and repeated egg counts in Schistosoma mansoni infections.

Faecal egg counts are often used to measure Schistosoma mansoni infection, but the considerable variation between successive counts complicates their interpretation. The stochastic model described in this paper gives a description of observed egg counts in a population and can be used as a tool to gain an insight into the underlying worm load distribution. The model distinguishes between two sources of variation in egg counts: (1) variation caused by the difference in worm load between individuals, and (2) the variability of egg counts for an individual with a given worm load. Empirical data, single and repeated measurements, from surveys in five villages in Burundi and Zaire have been used to fit and validate the model. We have discussed possible mechanisms that explain the differences in estimated values between the villages. The model indicates that the expected number of eggs in a stool sample per S. mansoni worm pair is lower than suggested by autopsy data and that, possibly as a consequence of immunity, the inter-individual variation in worm loads decreases with age.

Adolescent↗
PubMed1992

Preventive Pap-smears: balancing costs, risks and benefits.

The pattern of spontaneous screening for cervical cancer by general practitioners and gynaecologists in The Netherlands is compared with an efficient screening policy resulting from a cost-effective study. Spontaneous screening tends to start and stop too early in a woman's life, and leaves too many women overscreened or unprotected. The combination in young age of a low incidence of invasive cancer and a high incidence of regressive lesions explains relative ineffectiveness and harmfulness of present screening practice. When screening would take place between ages 30 and at least 60, with intervals of about 5 years, as many lives could be saved for half the costs and with only 60% of the unnecessary referrals and treatments. Much attention should be paid to the coverage of the target population. Therapeutic follow-up policies for dysplastic lesions should be restrained.

Age Factors↗
PubMed1992

The nature of excess mortality in nursing home patients with dementia.

Survival and excess mortality in 606 dementia patients admitted to a psychogeriatric nursing home were analyzed in a historical prospective 8-year follow up. The overall 2-year survival rate after admission was 55%, 60% for women and 39% for men. Patients with senile dementia of the Alzheimer's type had higher 2-year survival rates than those with multi-infarct dementia (57% vs 41%). Physical impairment, inactivity, dependency as measured on an observational scale, and comorbidity had an adverse effect on survival. Diseases with the lowest two-year survival were myocardial infarction, heart failure, atrial fibrillation, parkinsonism, pulmonary infection, anemia, pressure sores, and malignancies. The mortality rates of dementia patients were higher than those of the general population, especially during the first months after admission. This excess mortality of dementia patients was better described by an additive than by a multiplicative factor, suggesting that dementia can primarily be regarded as an independent, competing mortality risk.

Aged↗
PubMed1992

Screening for unruptured familial intracranial aneurysms. A decision analysis.

Decision analysis is used to assess the decision to screen for unruptured intracranial aneurysms (IAs) in two affected families, and to formulate guide-lines for similar decisions. Four strategies are compared: "no screening", "screening directly", "screening twice", and "screening later". Intravenous and intra-arterial digital subtraction angiography techniques (iv-DSA, ia-DSA) are considered. Life years lived with and without disability are computed for each strategy. Loss of life expectancy with and without discounting and quality correction is used as an outcome measure. "No screening" is the preferred strategy when population based estimates of the prevalence of IAs are used. Thus, the results of this analysis provide no justification for screening patients without a familial history. But a physician who thinks that the risk of an IA is increased may rightly decide for screening, especially when the patient is aged 40 to 60. Ia-DSA is preferable over iv-DSA. A scenario analysis suggests that screening with magnetic resonance angiography is only slightly better than with ia-DSA, because the complication rate of screening plays a minor role in the analysis.

Adult↗
PubMed1992

Is cerebral angiography indicated in infective endocarditis?

BACKGROUND AND PURPOSE: Patients with infective endocarditis may develop intracranial mycotic aneurysms. Whether these patients should undergo cerebral angiography followed by prophylactic surgery if an aneurysm is detected is an unresolved question. METHODS: We estimated the probability of survival 12 weeks after the diagnosis of infective endocarditis on the basis of data available in the literature. RESULTS: For a 40-year-old female patient with right-sided hemiplegia, the 12-week survival is estimated to be 83.75% without angiography and 83.65% with angiography; the specific mortality of intracranial mycotic aneurysms is relatively small but increases by 40% (from 0.25% to 0.35%) if angiography is performed. The risk of aneurysm rupture in infective endocarditis and the mortality from rupture appear to be the most important factors that affect the analysis. CONCLUSIONS: Cerebral angiography should not be performed routinely in patients with infective endocarditis. Specific subgroups in whom such a policy might be beneficial have not yet been identified.

Adult↗
PubMed1992

Management of children with acute pharyngitis: a decision analysis.

BACKGROUND: Although the incidence of acute rheumatic fever has declined in the last decades, a few outbreaks have recently been reported. A rapid latex agglutination test for group A streptococci seems reasonably accurate, and early treatment of acute pharyngitis seems to influence the pharyngitis itself. These factors have promoted uncertainty concerning the current best management of patients with sore throat. METHODS: Clinical decision analysis is used to compare the risks and benefits of symptomatic treatment, and oral and intramuscular penicillin as therapeutic options, and the throat culture and the rapid latex agglutination test as diagnostic strategies. Best estimates of the risk of streptococcal pharyngitis, its complications, the carrier rate, the accuracy of diagnostic tests, the efficacy of antibiotic treatment, allergic reactions, medication compliance, and health outcomes are combined into a management advisory. All results are subjected to a sensitivity analysis in order to check their strength against plausible changes in assumptions. Quality adjusted life days (QALD) lost are used as an outcome measure. RESULTS: The agglutination test combined with oral penicillin yielded the lowest expected loss (.50) of QALD for a typical child with a risk of harboring streptococci of .60. The other strategies, however, yielded losses that were only several hundredths of QALD higher. CONCLUSIONS: For children with at least a 40% chance of harboring streptococci and a duration of complaints of less than 2 days before starting treatment, diagnostic testing and prescription of oral penicillin appear to be the best choice of initial management. The rapid latex agglutination test is more effective than the throat culture, because prompt penicillin treatment after a positive test result may shorten the duration of pharyngitis in infected children. High rates of acute rheumatic fever (over 5 X 10(-4] and low medication compliance change the best strategy to agglutination test with intramuscular administration of penicillin.

Acute Disease↗
PubMed1992

Test selection in jaundice: a comparison between physician behavior and a diagnostic model.

The results of an observational study aimed at a formal assessment of clinicians' test-selection behavior are presented. We first make a proposal for diagnostic test usage in the latter phases of jaundice diagnosis. Next we compute a probabilistic estimate of the patient diagnosis, based on the COMIK algorithm. From the proposal and the probabilistic estimate we can predict the "test-selection behavior" of clinicians. The assessment follows from a tabulation of the predicted behavior against the tests selected by clinicians. It is shown that for most tests, the predictions are consistent with the observed test-selection behavior at a statistically significant level. Discussions of discrepancies between prediction and observation, and reasons for deviations from general guidelines, provide new dimensions for medical education. The methodology applied is a useful tool to improve medical care for the jaundiced patient.

Algorithms↗
PubMed1991

Delaying childbearing: effect of age on fecundity and outcome of pregnancy.

OBJECTIVES: To study the age of the start of the fall (critical age) in fecundity; the probability of a pregnancy leading to a healthy baby taking into account the age of the woman; and, combining these results, to determine the age dependent probability of getting a healthy baby. DESIGN: Cohort study of all women who had entered a donor insemination programme. SETTING: Two fertility clinics serving a large part of The Netherlands. SUBJECTS: Of 1637 women attending for artificial insemination 751 fulfilled the selection criteria, being married to an azoospermic husband and nulliparous and never having received donor insemination before. MAIN OUTCOME MEASURES: The number of cycles before pregnancy (a positive pregnancy test result) or stopping treatment; and result of the pregnancy (successful outcome). RESULTS: Of the 751 women, 555 became pregnant and 461 had healthy babies. The fall in fecundity was estimated to start at around 31 years (critical age); after 12 cycles the probability of pregnancy in a woman aged greater than 31 was 0.54 compared with 0.74 in a woman aged 20.31. After 24 cycles this difference had decreased (probability of conception 0.75 in women greater than 31 and 0.85 in women 20.31). The probability of having a healthy baby also decreased--by 3.5% a year after the age of 30. Combining both these age effects, the chance of a woman aged 35 having a healthy baby was about half that of a woman aged 25. CONCLUSION: After the age of 31 the probability of conception falls rapidly, but this can be partly compensated for by continuing insemination for more cycles. In addition, the probability of an adverse pregnancy outcome starts to increase at about the same age.

Adult↗
PubMed1991

The reproductive lifespan of Onchocerca volvulus in West African savanna.

The epidemiological model ONCHOSIM--a model and computer simulation program for the transmission and control of onchocerciasis--has been used to determine the range of plausible values for the reproductive lifespan of Onchocerca volvulus. Model predictions based on different lifespan quantifications were compared with the results of longitudinal skin-snip surveys undertaken in 4 reference villages during 13 to 14 years of successful vector control in the Onchocerciasis Control Programme in West Africa. Good fits between predicted and observed trends in skin microfilarial loads could be obtained for all villages. It is concluded that the reproductive lifespan of the savanna strain of O. volvulus lies between 9 and 11 years, and that 95% of the parasites reach the end of reproduction before the age of 13 to 14 years.

Africa, Western↗
PubMed1991

Epidemiological evidence for age-dependent regression of pre-invasive cervical cancer.

Data from the screening programme in British Columbia are used to test hypotheses about the natural history of cervical cancer, especially about progression and regression of preclinical lesions (dysplasia and carcinoma in situ). Three models are considered. A model without regression does not give an adequate fit of the data (P less than 0.001), and results in an implausible estimate of 33 years for the mean duration of pre-invasive lesions. A model with an equal regression rate at all ages still does not result in a good reproduction of the data. A good fit is achieved for a model with different regression rates in lesions that develop under and over age 34. Under age 34, 84% of the new lesions will regress spontaneously, with a 95% confidence interval of 76-92% regression. Over age 34, we estimate that 40% of the new lesions will regress. The average duration of dysplasia + CIS is 11.8 years, and the sensitivity of the Pap-smear is 80%. It is concluded that a considerable proportion of pre-invasive lesions in young women do not progress. The findings about progression and duration of pre-invasive lesions do not support the still prevailing tendency of frequently making Pap smears in young women.

Age Factors↗
PubMed1991

Survival of patients with dementia.

The evidence on survival in dementia is summarized. There are no reliable data on survival after onset of dementia or after first contact with medical services. People with dementia in outpatient clinics and nursing homes have 2-year survival rates of 75% (range 60%-95%) and 50% (range 30%-65%), respectively. Differences in survival between patients with senile dementia of the Alzheimer's type (SDAT) and multi infarct dementia (MID) are small. Women in nursing homes have a better prognosis than men (2-year survival rates, 60% vs 40%). Dementia patients have a considerable excess mortality when compared to the vital statistics. There is no evidence for improvement of survival rates during recent decades. Recommendations for future studies are made.

Alzheimer Disease↗
PubMed1991

[Falling and getting up in a psychogeriatric nursing home. 2-year Incident Reports Resident Care].

In 1988 and 1989 2880 incidents were reported in the psychogeriatric nursing home Stadzicht in Rotterdam. The incidents consist mainly of patient-falls (40%) or patients being found on the floor (29%). A patient falls approximately 2 times a year and is found on the floor approximately 1.5 times a year. Male patients ran a greater risk of falling than female patients. The incidents occur especially during the daytime in the living room or the hall. In 41 (2%) incidents the consequences for the patient are serious, including 28 hipfractures. Intrinsic factors (such as gender) are more important risk factors for falling than extrinsic factors (environment or the use of physical restraints). Several risks are therefore inevitable. The extrinsic factors are most suitable for prevention in the short run. Furthermore, it is necessary to asses patients on admission in terms of proneness to falls.

Accidental Falls↗
PubMed1991

The risk and dynamics of onchocerciasis recrudescence after cessation of vector control.

Using a computer simulation study, we have investigated the risk and dynamics of onchocerciasis recrudescence after stopping vector control, in order to provide guidelines for operational decision-making in the Onchocerciasis Control Programme in West Africa (OCP). For this purpose, we used the microsimulation model ONCHOSIM to predict for periods of 9-15 years of vector control the ensuing risk and dynamics of recrudescence in an onchocerciasis focus. The model was quantified and validated using OCP evaluation and field research data. A range of plausible values was determined for important confounding parameters, i.e., vector biting rate, variation in exposure between individuals, parasite life span, and the relation between skin microfilarial load and vector infection. Different model quantifications were used in order to take account of the possible confounding effect of these parameters on the prediction of recrudescence. In the absence of immigration of infected humans or invasion by infected flies, the model predicts that 14 years of full-scale vector control are required to reduce the risk of recrudescence to less than 1%. The risk depends, in particular, on the vector biting rate, and this has implications for the planning of post-larviciding surveillance. Recrudescence will be a relatively slow process, and its rate will depend on the duration of vector control. Even if vector control were stopped too early, i.e., after 12-13 years in a highly endemic area, it would take more than 20 years before the intensity of infection in the community would reach levels of public health importance.

Africa, Western↗
PubMed1991

[Subscales of the BOP (Assessment Scale for Elderly Patients) in psychogeriatrics].

The BOP (a rating scale for elderly patients) and its subscales are used in many nursing homes in the Netherlands. The subscales are the result of a factor analysis, based on data gathered in physically handicapped, psychogeriatric and elderly psychiatric patients. We assessed the reproducibility of these subscales for data only related to psychogeriatric patients. Therefore we gathered the rating scale scores on admission of 569 patients with dementia and analysed them. The subscales Dependency, Social Disturbance and Orientation & Communication were recognisable as a factor and did not differ much from the original subscales. The subscales Depression, Inactivity and Physical Impairment could not be identified as a factor. A new subscale 'Nocturnal behaviour' was formed. The most important reason for the dissimilarities in the 2 analyses seems to be the fact that the recent analysis is only based on assessment of psychogeriatric patients.

Activities of Daily Living↗
PubMed1990

A model for breast cancer screening.

A model for breast cancer screening has been developed. When the appropriate screening policy is specified, the model reproduces the detection rates and the incidence of interval cancers as observed in the recent screening projects in Utrecht and Nijmegen, the Netherlands. The model-predicted mortality rate reduction is in accordance with the results of the Kopparberg/Ostergötland randomized trial in Sweden. Key parameters of the model are the duration of the preclinical stages and the sensitivity of mammography. The average duration is approximately 2 years at age 40 and increases to approximately 5 years at age 70. The sensitivity is high (approximately 95%) for tumors larger than 1 cm. The model is used in the prospective evaluation of effects and costs of various screening policies.

Adult↗