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Biomedical subjects

T A DeRouen

Publications and source records attributed to T A DeRouen.

At least 19 recordsLinked to original sources
PubMed1992

A cohort study of the risk of cervical intraepithelial neoplasia grade 2 or 3 in relation to papillomavirus infection.

BACKGROUND: Human papillomavirus (HPV) has been associated with cervical intraepithelial neoplasia, but the temporal relation between the infection and the neoplasia remains unclear, as does the relative importance of the specific type of HPV, other sexually transmitted diseases, and other risk factors. METHODS: We studied prospectively a cohort of 241 women who presented for evaluation of sexually transmitted disease and had negative cervical cytologic tests. The women were followed every four months with cytologic and colposcopic examinations of the uterine cervix and tests for HPV DNA and other sexually transmitted diseases. RESULTS: Cervical intraepithelial neoplasia grade 2 or 3 was confirmed by biopsy in 28 women. On the basis of survival analysis, the cumulative incidence of cervical intraepithelial neoplasia at two years was 28 percent among women with a positive test for HPV and 3 percent among those without detectable HPV DNA: The risk was highest among those with HPV type 16 or 18 infection (adjusted relative risk as compared with that in women without HPV infection, 11; 95 percent confidence interval, 4.6 to 26; attributable risk, 52 percent). All 24 cases of cervical intraepithelial neoplasia grade 2 or 3 among HPV-positive women were detected within 24 months after the first positive test for HPV. After adjustment for the presence of HPV infection, the development of cervical intraepithelial neoplasia was also associated with younger age at first intercourse, the presence of serum antibodies to Chlamydia trachomatis, the presence of serum antibodies to cytomegalovirus, and cervical infection with Neisseria gonorrhoeae. CONCLUSIONS: Cervical intraepithelial neoplasia is a common and apparently early manifestation of cervical infection by HPV, particularly types 16 and 18.

Adolescent↗
PubMed1992

Quantification of periodontal attachment at multi-rooted teeth.

The purpose of the present study was to estimate the lost attachment surface area (LAS) and the remaining attachment surface area (RAS) of molars from a combination of clinical and radiographic measurements. Clinical and radiographic measurements on 32 maxillary and 26 mandibular molars were correlated with the post-extraction measurements of LAS and RAS. The results indicate that linear models may increase the precision of the estimate of LAS by a factor of 1.2 for maxillary molars and 1.4 for mandibular molars when compared to estimates of LAS using only attachment level measurements. A diagnostic model for RAS predicts the square root of the remaining attachment surface area with the information obtained from the remaining radiographic attachment area and a gingivitis index. It is concluded that modeling of periodontal data may provide a method for predicting lost and remaining periodontal attachment area of molar teeth.

Adult↗
PubMed1992

Validity issues in split-mouth trials.

The main purpose of the split-mouth design is to remove all components related to differences between subjects from the treatment comparisons. By making within-patient comparisons, rather than between-patient comparisons, the error variance (noise) of the experiment can be reduced, thereby obtaining a more powerful statistical test. Unfortunately, comparisons made on a within-patient basis have potential disadvantages. Treatments may have effects on experimental units other than those which they were assigned to (carry-across effects). Such effects cannot be estimated from split-mouth data. Neither can treatment effects be estimated. The estimable parameter in a split-mouth design is the treatment effect plus the sum of all carry-across effects. Unless a priori knowledge indicates that no carry-across effects exist, reported estimates of treatment efficacy are potentially biased. In the design of split-mouth clinical trials, potential gain in precision should be carefully weighed against a potential decrease in validity.

Humans↗
PubMed1992

The power of tests to detect differences between periodontal treatments in published studies.

10 studies comparing periodontal treatment modalities were re-examined to see if they had adequate power to detect true differences. Attachment level (AL) and pocket depth (PD) were the 2 variables assessed. A statistical test's power refers to its probability of detecting a significant sample difference in treatment means, given a predetermined value for alpha (level of significance), delta (a clinically meaningful underlying difference), and the sample size. Studies were included that stratified their data by initial pocket depths, reported sample size, and lasted at least 6 months. Power calculations were done for 173 treatment comparisons, using delta = 0.5 mm and alpha = 0.05. For shallow pockets (1-3 mm), most studies had a strong chance of detecting true differences (median power = 83%). For moderate pockets (4-6 mm), median power dropped to 38%. However, median power dropped to 14% for deep pockets (> 6 mm), with 75% of the tests having less than a 20% chance of detecting a 0.5 mm difference. Many of the modalities reported as "not significantly different" from each other have not had a fair trial, especially for deep pockets. In order to improve a study's power, 4 factors are discussed: the number of compared treatments, the expected noise or random error, the patient sample size, and the average number of sites per patient for each pocket depth category.

Analysis of Variance↗
PubMed1992

Design issues specific to studies of periodontitis.

Guidelines for clinical trials demonstrating equivalence or superiority for treatments for periodontitis are badly needed because of the great variety of drugs, agents, and devices now being developed. This paper focuses on three design issues. These are primary outcome variables and their measurement, disease-active vs disease-inactive sites and patients, and study duration. Determinants for selection of outcome variables include the biologic events to be observed, changes that are specific for periodontitis, and methods chosen to detect those changes. The primary outcome variables specific for periodontitis and appropriate for use in clinical trials are periodontal attachment level and alveolar bone status. Improved methods for measurement of both with excellent accuracy and reproducibility are now becoming available. Studies performed on untreated patients over the past decade demonstrate clearly that disease-active and disease-inactive pockets exist, at any given point in time most are inactive, disease progression is episodic and in most patients infrequent, and a rather small portion of the population--possibly around 5%--are unusually susceptible to rapid disease progression. These observations need to be taken into account in enrolling subjects into periodontitis clinical trials. Conducting a prestudy to identify actively diseased sites and susceptible subjects, or screening to enrich the proportion of active sites, is recommended. Determination of study duration is a very complex issue. It is related to the length of time required for maximal change and stabilization to occur in the biological events to be observed, the outcome variable(s) used to detect change, and the nature of the therapeutic interventions to be studied. No single duration is applicable to all periodontitis clinical trials. Large gaps in our knowledge about the design of periodontitis trials still exist, and additional research is needed.

Alveolar Bone Loss↗
PubMed1992

Determination and selection of the optimum number of sites and patients for clinical studies.

Calculating required sample sizes is a critical step in the design of any study. For dental studies, the sample size needs to be specified at two levels: (1) the number of patients (n) enrolled in the study, and (2) the average number of sites (m) examined per patient. In general, m and n should be selected in such a way that the precision of the research findings is maximized, while the cost of the study is minimized. This objective can be realized by taking stock of the components of variation and the costs involved with enrolling patients and examining sites. The research cost for n patients ($C1/patient), at an average of m sites per patient ($C2/site), can usually be approximated by nC1 + nmC2. The precision varies as a function of the variance components, m, and n. To optimize precision for a fixed cost, the average number of sites examined per patient (m(opt)) should be approximately equal to [formula: see text] where rho is the within-patient correlation coefficient of the site-specific variable measured. When m(opt) is approximately equal to or in excess of the average number of sites available per patient, whole-mouth examinations are indicated. When m(opt) is considerably smaller than the average number of sites available, the sample of optimum size should be obtained by some random mechanism. Examination of a number of sites considerably different from m(opt) results in a waste of resources, regardless of the number of patients studied. Standard statistical analyses for determination of the patient sample size required to obtain a pre-specified precision or power are discussed.

Colony Count, Microbial↗
PubMed1991

Cromolyn versus triamcinolone acetonide for youngsters with moderate asthma.

Although both cromolyn (C) and inhaled corticosteroids are anti-inflammatory therapies for childhood asthma, there are few controlled comparisons of these medications for asthma therapy in children. None were conducted in the United States, and none specifically study triamcinolone acetonide (T) versus C. This 12-week evaluation followed 31 youths, aged 8 to 18 years, with moderate asthma who were assigned to receive C or T according to a prerandomized and blinded code. Patients were instructed to take two inhalations from the study metered-dose inhaler (active T or placebo) and to inhale the contents of one study-provided ampule (C, 20 mg, or placebo) from a compressor-driven home nebulizer three times per day. Patients also used albuterol, two inhalations from a metered-dose inhaler, three times a day (before study medication) and, additionally, if needed. Patients maintained a daily diary, recording extra medication use, adverse experiences, peak flow rates morning and night, and asthma symptom scores. Laboratory assessment of pulmonary function was done at 1, 4, 8, and 12 weeks. Cosyntropin challenge and methacholine bronchoprovocation challenge were performed at the beginning and end of the study. C and T provided similar, adequate asthma control. Symptoms of wheezing, cough, and chest tightness decreased, and daily peak expiratory flow rate increased with both regimens compared to during a 2-week baseline when patients received medication only as needed. There was no significant change in methacholine sensitivity and no change in endocrine function, as measured with fasting plasma control before and after administration of cosyntropin.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1991

Measures of dental disease occurrence.

The purpose of the paper is to relate standard epidemiologic and statistical methods for measures of disease occurrence to the description of prevalence proportions and incidence rates of dental diseases. No new concepts are introduced, but the choice of the unit of analysis of numerator and denominator is discussed, and the biological interpretation of the within-patient correlation coefficient is discussed.

Cluster Analysis↗
PubMed1990

Relationship between gingival crevicular fluid levels of aspartate aminotransferase and active tissue destruction in treated chronic periodontitis patients.

Data from several sources demonstrate that disease-active and disease-inactive periodontal pockets exist, and that disease progression occurs in bursts of activity. Currently used diagnostic procedures do not distinguish between disease-active and disease-inactive sites at any given point in time. We report the results of studies aimed at determining whether levels of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) are associated with disease activity as assessed by the level of gingival inflammation and probing attachment loss. 25 previously treated periodontitis patients participating in a quarterly recall maintenance program, who had experienced recurrent periodontal deterioration, served as experimental subjects. Patients were evaluated at 3-month intervals for 2 years. Values for plaque index, gingival index, and probing attachment level were recorded, and 30-second samples of gingival fluid harvested from the mesiobuccal aspect of the 4 first molars and the distal of the 4 lateral incisors. GCF volume was measured using a Periotron 6000, and AST activity was measured by a standard method. Sites were ranked in a hierarchy based on the degree of certainty of attachment loss as well as the severity of gingival inflammation, and the relationship of the values to AST levels was determined. Three models were used to analyze the resulting data, and all led to the same conclusion. Maximum enzyme level was significantly elevated at sites with confirmed disease activity as assessed by attachment loss, with maximum AST levels 725 units higher at these sites, on average, than at other sites (p less than 0.0001). Our data support the idea that an objective diagnostic test, based on levels of AST in GCF, that distinguishes between disease-active and disease-inactive sites may be possible.

Aspartate Aminotransferases↗
PubMed1990

Relationship between levels of aspartate aminotransferase in gingival crevicular fluid and gingival inflammation.

Data from several sources demonstrate that disease-active and disease-inactive periodontal pockets exist, but currently available diagnostic procedures do not permit identification of disease-active sites at any given point in time. Using the experimental gingivitis model, we have performed studies aimed at determining whether levels of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid correlate with the presence and extent of periodontal inflammation. Gingival inflammation was assessed using the Gingival Index and the Sulcular Bleeding Index, and enzyme activity was measured using a standard procedure. Our data reveal a statistically significant association between AST values and Gingival Index scores for spontaneously occurring lesions (p less than 0.02-0.04) and experimentally induced lesions (p less than 0.0001), as well as the extent of change in these values during developing experimental gingivitis (p less than 0.0001) and resolving experimental gingivitis (p less than 0.0001). The data demonstrate that AST levels can be used to assess the presence and extent of periodontal inflammation.

Adolescent↗
PubMed1990

Assessment of relationships between site-specific variables.

The assessment of relationships between site-specific variables has been a matter of controversy because of the claim that periodontal sites within individuals can be used as independent observations in statistical models. One problem with this approach is the unreliability of the calculated Type I and Type II error rates. Another problem is that such inappropriate analysis may prohibit a correct assessment of causal relationships between site-specific variables. The host-factor can act as an effect modifier and modulate the magnitude of the site-specific effects and/or the host-factor can act as a confounder by superimposing a patient-effect on the studied site-specific effects leading to bias. As a result, site-specific biological mechanisms of disease progression may be misinterpreted. Sites can be used as the experimental unit of analysis, but the sampling design from which the site-specific data originated should not be ignored.

Causality↗
PubMed1979

Effect of surgical versus medical therapy on return to work in patients with coronary artery disease.

The proportion of medically and surgically treated patients with coronary artery disease working full time 1 year after cardiac catheterization or surgery, respectively, was assessed by questionnaire in a registry of patients who had had coronary angiography. The proportion of medically and surgically treated patients working 3 months before catheterization or surgery was 74 percent (148 of 201) and 75 percent (899 of 1,198), respectively, whereas 62 percent (125 of 201) and 62 percent (747 of 1,198), respectively, were working full time 1 year after catheterization or surgery. Multivariate analysis identified five variables predictive of return to work. In order of significance these were: working status 3 months before surgery or catheterization, years of education, age, functional class before surgery or catheterization and period of not working before surgery or catheterization. Work status 3 months before surgery or catheterization was clearly the best predictor of continued employment 15 months later. Surgical therapy was not more effective than medical therapy in maintaining full-time employment in this registry of patients with coronary artery disease.

Age Factors↗
PubMed1979

Variables predictive of survival in patients with coronary disease. Selection by univariate and multivariate analyses from the clinical, electrocardiographic, exercise, arteriographic, and quantitative angiographic evaluations.

A progression of univariate followed by multivariate analyses was applied to 46 variables selected from the clinical examination, exercise test, coronary arteriography, and quantitative angiographic assessment of left ventricular function in patients with coronary disease to determine those variables most predictive of survival. For the 733 medically treated patients, the final Cox's regression analysis showed that the left ventricular ejection fraction was most predictive of survival, followed by age, number of vessels with stenosis(es) greater than or equal to 70%, and ventricular arrhythmia on the resting electrocardiogram. For the 1870 surgically treated patients, ventricular arrhythmia on the resting electrocardiogram was most predictive of survival followed by ejection fraction, heart murmur, left main coronary artery stenosis greater than or equal to 50%, and use of diuretic agents.

Adult↗
PubMed1979

Evidence from a nonrandomized study that coronary surgery prolongs survival in patients with two-vessel coronary disease.

Within the larger Seattle Heart Watch arteriography registry, surgically treated patients non randomly selected for direct myocardial revascularization were matched to medically treated patients such that each of the 287 pairs was identical in seven variables (ejection fraction, ventricular arrhythmia on resting electrocardiogram, age, heart murmur, stenosis of left main coronary artery greater than or equal to 50%, number of vessels with stenosis greater than or equal to 70%, and use of diuretics) previously demonstrated to be independently predictive of survival. Actuarial survival analyses based on cardiovascular deaths (average follow-up 3.5 years) indicate improved survival for the entire surgical matched pair cohort (p = 0.008) and for the surgically treated subgroup with two-vessel disease (p = 0.0002) when compared to the medical cohort. These results were confirmed by examination of the entire arteriography registry (n = 1524) in which these seven variables were known, using Cox's model for survival analysis. This multivariate, statistical technique indicated that the surgical mode of therapy was significantly predictive of improved survival in surgically treated patients for the entire registry (p = 0.008) and for the subgroup with two-vessel disease (p = 0.0005).

Adult↗
PubMed1979

Noninvasive screening criteria for enhanced 4-year survival after aortocoronary bypass surgery.

Two thousand one men with coronary heart disease (CHD) who were enrolled in the Exercise Testing Registry of the Seattle Heart Watch had symptom-limited maximal exercise tests at the initial clinical examination and follow-up surveillance of subsequent mortality for 4.1 +/- 1.6 years. When subdivided into three mutually exclusive subgroups, 636 patients did not have exertional myocardial ischemia, left ventricular dysfunction or cardiomegaly; 885 without cardiomegaly had only exertional ischemia; 480 had left ventricular dysfunction by either cardiomegaly and/or two noninvasive exertional criteria, with or without exertional myocardial ischemia. Three hundred thirty-one men had aortocoronary bypass surgery, while 1670 remained unopened for at least 4 years. Only 34% of the operated patients who had left ventricular dysfunction, as defined, showed a marked improvement in 4-year survival rates (p less than 0.01). Differences in the annual CHD mortality rates in relation to surgical treatment in the other two groups were not statistically significant. Restricting the analysis to a subset of patients who had invasive studies did not alter the conclusion. Accordingly, we suggest the use of noninvasive criteria to aid preliminary screening of patients for invasive studies and surgical treatment.

Adult↗
PubMed1978

Myocardial imaging with 201thallium: an analysis of clinical usefulness based on Bayes' theorem.

Rest-exercise thallium-201 (201Tl) myocardial imaging and rest-exercise electrocardiography were performed in 137 patients with suspected coronary artery disease (CAD). The final diagnosis of coronary disease was made by arteriography. Sensitivity and specificity for the ECG and thallium studies alone or combined were then determined. Based on these data, the posttest probability of CAD with a normal or abnormal test was calculated using Bayes' theorem for disease prevalences ranging from 1%--99%. The difference between the probability of disease with a normal test and the probability of disease with an abnormal test was also calculated for each prevalence range. The results demonstrate that 201Tl imaging discriminates between disease absence or presence better than does the ECG. However, both the ECG and thallium studies provide rather poor discrimination between disease and no disease when the disease prevalence is low (less than 0.20) or high (greater than 0.70). Because of this characteristic, it is unlikely that screening tests for CAD will prove useful unless the disease prevalence in the group under study is in the moderate (0.20--0.70) range.

Angiography↗
PubMed1978

Exercise testing as a predictor of heart disease and sudden death.

Analysis of data obtained from symptom-limited exercise testing and standard clinical evaluation has identified certain variables as having marked prognostic significance in coronary disease, making it possible to separate patients at highest risk of sudden death from the vast majority. The way is thus opened for focusing aggressive preventive efforts upon the group most likely to achieve the greatest benefit.

Age Factors↗