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Biomedical subjects

H Straatman

Publications and source records attributed to H Straatman.

At least 55 records · Page 3Linked to original sources
PubMed1996

Age-specific sensitivities of mammographic screening for breast cancer.

The sensitivity of the mammographic screening test in the biennial screening program of Nijmegen is assessed by analyzing the occurrence of interval cancers, i.e. cancers surfacing clinically in the interval between a negative screening examination and the subsequent scheduled examination. The difference between the observed number of interval cancers and the expected number of clinically manifest cancers in the absence of screening for the interval period reflects the number of cancers detected by screening. The expected number should be limited by the number of those cancers that were not detectable at the time of the screening examination because their size was under the threshold of mammographic detectability (5 mm). In contrast to other sensitivity studies we took these 'fast growing' cancers into consideration, the numbers of which are estimated in each of the six-month periods of the two-year interval using age-specific tumor volume growth rates for three age groups: < 50, 50-69, and > or = 70 years. In patients under age 50, the sensitivity was 64% for cancers which would become clinically manifest within one year after screening. This sensitivity was lower than those obtained from the 50-69 and > or = 70 age groups, being 85% and 80%, respectively. For cancers that would become clinically manifest 12-18 months after screening, sensitivity decreases to 22% in the under age 50 group, and to 56% and 65% in the two above age 50 groups, respectively. We conclude that even when adjusted for growth rate, the mammographic screening test has a poor performance in the under age 50 group.

Adult↗
PubMed1996

Decreasing bladder cancer mortality in The Netherlands.

OBJECTIVE: To evaluate the prediction that the observed increasing trend in male bladder cancer mortality in the Netherlands between 1955 and 1988 would change to a decreasing trend. MATERIALS AND METHODS: Using demographic and mortality data from the Netherlands Central Bureau of Statistics, male and female bladder cancer mortality per 10(5) person-years from 1955 to 1994 were calculated. Changes in the age structure of the Dutch population were adjusted using direct standardization to the European "standard' population. The effects of age, calendar period and birth cohort on the temporal trend in mortality were evaluated using log-linear modelling. RESULTS: Male mortality from bladder cancer increased from 6.2 per 10(5) in 1955 to 12.6 per 10(5) in 1990, but decreased thereafter. Female mortality from bladder cancer has remained stable throughout the study period, at 2.8 and 2.7 per 10(5) in 1955 and 1994, respectively. The changing trend among men is consistent with an increasing risk for successive birth cohorts until the 1910 cohort and a decreasing risk for cohorts born after 1930. This cohort effect is probably caused by changes in the smoking behaviour of the male Dutch population. There were no differences in risk for successive birth cohorts of females. CONCLUSION: Male mortality from bladder cancer in the Netherlands will probably decrease for at least another decade. A future increase in female mortality from bladder cancer, as recorded for lung cancer, is unlikely.

Adult↗
PubMed1996

Prognostic models for the probability of achieving an ongoing pregnancy after in-vitro fertilization and the importance of testing their predictive value.

The aim of this study was to create reliable models to predict the probability of achieving an ongoing pregnancy during in-vitro fertilization (IVF) treatment: model A, at the start of the first treatment, model B at the time of embryo transfer, and model C, during the second treatment at the end of the first IVF treatment. Prognostic models were created using data from the University Hospital Nijmegen (n = 757) and applied to the data from the Catharina Hospital Eindhoven (n = 432), The Netherlands, to test their predictive performance. The predictions of model B (made at time of embryo transfer) were fairly good (c = 0.672 in the test population). For instance, 93% of the patients who had a predicted probability of achieving an ongoing pregnancy of < 10% did not achieve an ongoing pregnancy. However, the predictions of the other two models (A and C) for Eindhoven were less reliable. The predictive value of model C was fairly high in Nijmegen (c = 0.673). Its poor performance in the test population may be explained partly by differences in effectiveness of the ovulation stimulation protocols and the decision about when to discontinue the cycle. Thus, before using prognostic models at an IVF centre, their reliability at that specific centre should be tested.

Evaluation Studies as Topic↗
PubMed1996

Seasonal variation in the time to pregnancy: avoiding bias by using the date of onset.

To study seasonality in human fecundability, measured indirectly by time to the first pregnancy, we used data from 18,970 French-Canadian women who married for the first time during the 17th or 18th century. The time to pregnancy was approximated by the interval between marriage and first birth minus 38 weeks. We used the week of marriage and the week of conception as references to study seasonality. We found a minor seasonal pattern in time to pregnancy when using the week of marriage as a reference. The proportions of women with a short time to pregnancy were highest during December-January and June-July, indicating that these may be the most fecund periods. In contrast, we found an obvious seasonal pattern when using the date of conception as a reference. This pattern can be largely explained by a strong seasonal pattern in pregnancy planning (in this case, in marriages). When studying seasonal variation in the time to pregnancy, the date of onset of the time to pregnancy should be used as reference, not the date of conception. Otherwise, results will be biased owing to seasonality in pregnancy planning. The same is true for studies on seasonally bound exposures in relation to time to pregnancy.

Adolescent↗
PubMed1996

Long term breast cancer screening in Nijmegen, The Netherlands: the nine rounds from 1975-92.

STUDY OBJECTIVE: To assess the performance of breast cancer screening in different age categories over two decades. DESIGN: Important determinants of reduced breast cancer mortality such as attendance, mammography performance, cancer detection, and disease stage were recorded. SETTING: Nijmegen, The Netherlands, 1975-92. SUBJECTS: Since 1975 more than 40,000 women aged 35 years and older have been invited biennially for breast screening in a population based project in Nijmegen. MAIN RESULTS: Rates of attendance, referral, detection, and disease stage were calculated, as well as the specificity of screening mammography and the predictive value of referral and biopsy. From round 3 onwards, the attendance rate of women younger than 50 years stabilised at 70%, in women of 50-69 years it was 62%, and in women aged 70 and over it was 22%. In these three age categories, the referral rates of a positive screening mammography per 1000 screened women were 4.9, 6.2, and 11.8, respectively. Specificity rates were between 99% and 100%. Current predictive values of referral were high: in the specific age categories 39%, 59%, and 68% of the referred women had cancer. Detection rates remained fairly stable over the rounds 4-9, at 1.9, 3.6, and 8.0 cancers per 1000 screened women. In the two year period between screening the numbers of interval cancers per 1000 screened women were 2.2, 2.2, and 2.9, for the three age categories respectively. With regard to invasive cancers detected during screening, the percentage of small tumours (< or = 20 mm on the mammogram) was 84% in each age category. For women younger than 50 years, the proportion of intraductal carcinoma in all the cancers detected at screening was 40%, while it was 15% in the other age categories. CONCLUSION: Throughout the nine rounds, the screening outcomes were found to be adequate, particularly considering the high specificity rate and the predictive value of referral without the interference of a low detection rate. Although the occurrence of interval cancers seemed high, it was similar to other screening programmes. Despite a relatively low referral rate, the ratios of screen detected versus interval cancer cases were favourable. Well organised screening programmes can achieve good mammography results without too many false positives. It is important that women continue to participate in a screening programme because cancer can still be detected even after several successive negative screening examinations.

Adult↗
PubMed1995

Sample size determination for a trial of breast cancer screening under age 50: population versus case mortality approach.

OBJECTIVE: To determine the efficacy of screening for breast cancer in women aged 40 to 49. METHODS: A large number of women will have to be enrolled to ensure adequate statistical power. Attention will be restricted to the deaths from breast cancer that occur among comparable groups of patients with breast cancer rather than to an analysis in which all women entering into the trial are considered at risk of dying from breast cancer (population mortality analysis). As the new trial is likely to be conducted in regions where screening has been established for all women from age 50 onward, comparability may be reached by including the breast cancers detected at the routine screening examination at age 50. CONCLUSIONS: When comparability of cases can be reached, such a case mortality analysis requires 15-30% fewer women to be enrolled than a population approach.

Adult↗
PubMed1994

Mortality trend from prostate cancer in The Netherlands (1950-1989).

The trend in prostate cancer mortality in The Netherlands was studied, using data from the National Causes of Death Registry of the Central Bureau of Statistics. During the period 1950-1989, the age-adjusted mortality rate showed a steady rise from 20.5 to 30.6 per 100,000 man-years. A multiplicative model was used to examine possible period effects and birth-cohort effects separately. This analysis demonstrated that the increase in prostate cancer mortality is largely due to a birth-cohort effect, though calendar time of death may have had a slight effect as well. Among Dutch men, a continuous increase of mortality from prostate cancer was found in consecutive birth cohorts. This finding is in contrast with that of comparable studies in other Western countries, in which a peak mortality rate was found for the cohort born at the end of the 19th century with stabilizing or declining rates for later birth cohorts.

Age Factors↗
PubMed1994

Efficacy of hydroquinine in preventing frequent ordinary muscle cramp outlasts actual administration.

In order to compare the efficacy of a daily dose of 300 mg hydroquinine hydrobromide and placebo in preventing frequent ordinary muscle cramp, we designed a randomized, double-blind, placebo-controlled study of three consecutive 2-week periods viz. a qualification period, a medication period and a wash-out period. Twenty healthy adult volunteers experiencing at least 3 muscle cramps a week (6 men, 14 women aged 38-78 yrs) were enrolled into this study, and 19 of them completed it. Hydroquinine hydrobromide (300 mg/day) was administered to group 1 (10 women) and placebo to group 2 (4 women, 6 men). The frequency, severity, duration and location of muscle cramps as well as short-term adverse drug effects were recorded in daily diaries. Compared with placebo the decrease in the mean number of muscle cramps (16.1 or 58%) in the active drug treatment group during the medication period was highly significant (Wilcoxon test p = 0.004). During the wash-out period this decrease partly persisted (8.9 or 33%). In this study a daily dose of 300 mg hydroquinine hydrobromide was effective in preventing frequent ordinary muscle cramp in healthy female volunteers. The effects of hydroquinine outlasted its administration. The drug was well tolerated.

Adult↗
PubMed1994

The capture-recapture method for estimation of cancer registry completeness: a useful tool?

BACKGROUND: In this paper we investigated whether the capture-recapture method is useful for a cancer registry to monitor its completeness of case ascertainment on a routine basis. METHODS: The capture-recapture method was used to estimate the completeness of case ascertainment in three regional cancer registries in the Netherlands, which are based on case finding by pathology laboratories and hospitals. RESULTS: Completeness was estimated to be 98.3%. The estimate of completeness was dependent on age and cancer site, with lower estimates of completeness for skin cancer and lymphatic and haematopoietic malignancies and for the age group > or = 75 years. CONCLUSIONS: A major drawback of the capture-recapture method is its inability to estimate the number of cases that are not routinely notified to the registry by one or both notification sources. Another limitation is the lack of statistical power to detect incompleteness in an early stage. It is concluded that the capture-recapture method is not useful for everyday surveillance of completeness in cancer registration.

Aged↗
PubMed1994

The effect of otitis media with effusion at preschool age on some aspects of auditory perception at school age.

The relationship between otitis media with effusion (OME) at preschool age and performance on five tests of auditory perception was studied in 89 school-age children who had OME histories well documented from participation in serial screening for OME at 2-4 yr of age. The tests used at 7.5-8 yr of age were: speech-in-noise, filtered speech, binaural fusion, dichotic speech, and auditory memory. A significant effect of OME was found on the speech-in-noise test. No additional effects were demonstrated by this particular group of children.

Audiometry, Pure-Tone↗
PubMed1994

Cancer incidence: life table risk versus cumulative risk.

STUDY OBJECTIVE: To study differences between various methods of estimating cancer risk in individuals. DESIGN: Information was obtained from a cancer registry. Lifetime risk was calculated using the life table method, taking competing causes of death into account and using well recognised methods such as the cumulative rate and risk. SETTING: Regional cancer registry of the Comprehensive Cancer Centre IKL, located in Maastricht, The Netherlands. PATIENTS: Patients with a first primary malignancy in 1989-90 in the catchment area of the cancer registry. MAIN RESULTS: The lifetime risk of developing cancer was estimated to be 34.8% for males and 30.4% for females. In males, especially, the risk estimates were considerably higher when the cumulative risk was used. CONCLUSIONS: The life table method is convenient for estimating the probability that a person will develop cancer during a defined period or during his or her lifetime. The other estimates overestimate the risk of the disease under investigation, especially in the very elderly.

Adolescent↗
PubMed1992

Trends in mortality from malignant cutaneous melanoma in The Netherlands, 1950-1988.

This paper presents an analysis of trends in mortality from malignant melanoma of the skin in The Netherlands, 1950-1988. Statistical analyses show that time period effects are needed to describe the mortality trends in The Netherlands. Because this contrasts with reports from other countries, in which the trends were ascribed to a cohort effect only, log-linear models including the three factors age, time period and birth cohort, were fitted to the data. To be able to separate time period effects from birth cohort effects we assumed a mathematical function for the mortality rates in relation to age. The results obtained in this way indicate that time period effects increased up to 1970. An increase of birth cohort effects is seen for cohorts born between 1900 and 1955. For cohorts born after 1955 the mortality from melanoma seems to decrease. The most plausible explanation for the time period effect probably is improvement in death certification.

Adolescent↗
PubMed1992

Bladder cancer mortality in The Netherlands, 1955-1988.

In 1955, 234 men and 116 women died from bladder cancer in the Netherlands. In 1988 the numbers were 794 and 317 respectively. After adjusting for the ageing of the Dutch population since 1955, female mortality rates per 10(5) person-years appear to be very stable: 2.9 from 1955 to 1959 and 3.0 from 1985 to 1988. By contrast, an increasing trend exists in males. From 1955 to 1959 and from 1985 to 1988, bladder cancer mortality rates per 10(5) person-years were 7.5 and 12.4 respectively. For men in particular, increasing mortality (and incidence) rates are seen all over the world. In many cases this increasing trend is thought to originate from a higher risk of dying from bladder cancer in successive birth cohorts rather than from a higher risk in successive calendar periods. This so-called cohort effect is explained by changes in smoking behaviour in the male population. Statistical modelling of bladder cancer mortality data from 1955 to 1988 in the Netherlands shows that the increasing temporal trend in men can also be described as a cohort effect. The risk of dying from bladder cancer increases from the 1875 birth cohort to the 1910 birth cohort, but decreases thereafter. It is concluded that this decreasing risk for generations born after 1910 will probably result in a decreasing trend in mortality in the near future, when more and more of these "youngsters" reach the age of 70+.

Age Factors↗
PubMed1990

The choice of a balanced allocation method for a clinical trial in otitis media with effusion.

We review the choice of treatment allocation procedures in a specific small clinical trial of the effect of tympanostomy tubes on language development in patients with otitis media with effusion. The options for balanced allocation available at the planning stage are discussed. A clearly favourable method could not be identified. A simulation study was performed, and its results demonstrated least imbalance with the variance method. In practice this method produced considerable imbalance on relevant prognostic factors.

Child, Preschool↗
PubMed1990

Shortcut method to calculate the sample size in trials of screening for chronic disease.

One of the first questions arising in the planning of a randomized trial to evaluate mortality reduction by screening concerns the sample size of the trial required to detect an expected mortality reduction in the study group for given significance level alpha, and power 1 - beta. If estimates exist of the underlying average annual incidence rate of the disease ra and the annual mortality rate delta a or survival data for patients in the population under consideration before screening started, then a simple formula for the probability of dying from the disease within T years after entry into the trial can be given for the control group. Standard formulas may then be used for sample size calculations in randomized trials, which compare the risk of death from the disease in the control and the study group accrued at T years after entry. A simple correction for loss of follow-up, due to mortality from other causes or, for instance, migration is possible.

Age Factors↗