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Biomedical subjects

P K Andersen

Publications and source records attributed to P K Andersen.

At least 19 recordsLinked to original sources
PubMed1992

Increasing incidence of early onset type 1 (insulin-dependent) diabetes mellitus: a study of Danish male birth cohorts.

To provide information of the incidence trends of Type 1 (insulin-dependent) diabetes mellitus we performed a cohort study of a series of Danish male birth cohorts. All male livebirths in Denmark between 1 January 1949 and 31 December 1964, were investigated regarding the development of Type 1 diabetes during the first 20 years of life using the files of the Danish Conscript Board, supplemented by a search in the Danish National Registry of Deaths. Diagnosis was verified and clinical information obtained from medical records. The material is estimated to be more than 95% complete. A total of 1705 diabetic subjects were identified of whom 23 were not representative of idiopathic Type 1 diabetes. The cumulative rate of Type 1 diabetes development during the first 20 years of life increased from 2.37 to 2.90 per 1000 for the first eight and last eight birth cohorts, respectively. A log-linear analysis of the incidence revealed significantly increasing incidence rates, independent of age effects, with a maximum in the late 1970's. About 75% of the cases presented short duration of symptoms prior to diagnosis, and only very few cases were diagnosed incidentally. Cases were diagnosed relatively less frequently during summer months than during winter months.

Adolescent↗
PubMed1992

Repeated assessment of risk factors in survival analysis.

Regression models for survival data with time-dependent covariates are considered. We review estimation in the Cox regression model and discuss problems in connection with data requirements for the analysis, with interpretation of results and with prediction based on such a model. In particular, we discuss how the latter problems may be approached within an extended (Markov process) model. A clinical trial in liver cirrhosis is used for illustration.

Clinical Trials as Topic↗
PubMed1992

Hypothermic patients admitted to an intensive care unit: a fifteen year survey.

In the period 1975-1989, 620 (4.5%) of 13,645 patients admitted to the intensive care unit of a Danish university hospital were diagnosed as suffering from hypothermia. The aim of the retrospective survey carried out is to describe this group of patients and to evaluate the methods used for rewarming. The degree of hypothermia was mild in 554 of the patients, moderate in 60, and severe in six. The rewarming method used was passive rewarming with the use of endogenous heat production. Rewarming was established with a median temperature increment of 0.1 to 2.5 degrees centigrade. The mortality rate showed no relationship to the hypothermia. With the exception of extracorporal circulation, the rewarming and mortality rates did not differ from the results shown in studies carried out using active and invasive rewarming procedures. In conclusion, with the exception of extracorporal circulation, rewarming of hypothermic patients by preservation of the endogenous heat production seems as effective as active and invasive rewarming methods.

Adolescent↗
PubMed1991

[Proved self-poisoning. A 10-year case load from an intensive care unit].

During the period 1.1.1979-31.12.1988, a total of 2.023 admissions (involving 1.511 patients) occurred on account of deliberate self-poisoning in the Intensive Care Unit of the Anaesthetic Department of Odense Hospital. No significant alterations were observed in the female/male ratio or in the average age, during this period. Duration of hospitalization in the Intensive Care Unit showed a decrease. The frequencies of cases of poisoning with barbiturates showed a decrease while poisonings with acetaminophen, alcohol and chemical-technical agents showed increasing frequencies. Poisoning with benzodiazepines, neuroleptics, polycyclic antidepressive drugs, dextropropoxyphen or acetylsalicylic acid occurred with unaltered frequency. Treatment consisted mainly of endotracheal intubation, artificial ventilation, circulatory therapy, forced alkaline diuresis, haemodialysis and antibiotic therapy. The frequency of forced alkaline diuresis decreased during the period while circulatory therapy, haemodialysis, antibiotic therapy and treatment with antidotes were employed increasingly frequently. The acute lethality was 1.6%. It is concluded that treatment was mainly symptomatic and concentrated on ensuring respiratory and circulatory functions and that the acute lethality is unchanged and will probably not be lowered further. The "Scandinavian method" is thus still the cornerstone in the treatment of poisoning and is responsible for the continued low acute lethality.

Adolescent↗
PubMed1991

Assessing the influence of reversible disease indicators on survival.

In a randomized clinical trial of the effect of prednisone versus placebo on survival in patients with liver cirrhosis, follow-up visits were scheduled after 3, 6 and 12 months of treatment and thereafter once a year. At each follow-up the prothrombin index, a measure of liver function, was recorded and scored as either low or normal. The interaction between treatment and prothrombin index was analysed using a three-state illness-death model with recovery. The continuous-time Markov process model with constant or piecewise constant intensities suggested by Kay allows inference to proceed even though the status of the disease indicator, here the prothrombin index, is only known at the time of each visit and not between visits. We compare the analysis with the theoretically incorrect, but practically rather common approximation, where the status of the disease indicator is assumed to remain constant from one visit until just before the next. Under this approximation both standard parametric methods and non-parametric approaches developed by Aalen and Johansen are available.

Clinical Trials as Topic↗
PubMed1991

Fibre-optic bronchoscopic evaluation of tracheal tube position.

Verification of tracheal tube position by fibre-optic bronchoscopy was evaluated in 20 critically ill adult patients. The distance between the carina and the tube was measured by direct visualization with a fibre-optic bronchoscope and compared with the corresponding measurement obtained from a concomitant chest radiograph. The measured values did not differ significantly and in 18 out of 20 patients the accuracy was within 2 cm. No adverse effects were observed. We conclude that verification of tracheal tube position by fibre-optic bronchoscopy is a safe alternative to chest X-ray.

Bronchoscopy↗
PubMed1990

Tumor cell concentration and tumor burden in relation to histopathologic subtype and other prognostic factors in early stage Hodgkin's disease. The Danish National Hodgkin Study Group.

Prognostic factors were examined by multivariate analysis after a recent follow-up of the 300 patients with Hodgkin's disease pathologic stage (PS) I or II treated with radiotherapy +/- adjuvant combination chemotherapy in the prospective randomized trial of the Danish National Hodgkin Study. Initial biopsy material was classified according to the Rye histopathologic classification, the grading and subclassification proposed by the British National Lymphoma Investigation (BNLI), and tumor cell concentration in sections. Tumor cell concentration as a prognostic factor turned out to be better than the other classifications. However, if macroscopic tumor burden was taken into account both tumor cell concentration and the other histopathologic classification systems lost their prognostic significance. Significantly, however, a combination of macroscopic tumor burden and tumor cell concentration, yielding an estimate of the total tumor cell burden, was even better than the macroscopic tumor burden as a prognostic factor. In conclusion, a simple tumor cell concentration count seems to be the most useful form of histopathologic subtyping for prognostic purposes in early stage Hodgkin's disease.

Hodgkin Disease↗
PubMed1990

pH in physiological salt solutions: direct measurements.

Calculations of pH in modified Krebs solutions by inserting PCO2 and total-CO2 in the Henderson-Hasselbalch (H.-H.) equation are obvious as the equation originally served for this purpose. An exact calculation of the relation between pH and PCO2 is complicated as the concentration of bicarbonate, the dissociation constant and the solubility of CO2 change. Furthermore, the dissociation constant in the H.-H. equation is constant only if activities are used in the equation instead of stoichiometric concentrations. We therefore investigated the influence of different carbon dioxide tensions and bicarbonate concentrations on directly measured pH of organ baths aerated with mass-spectrometric analyzed O2-CO2 gases. For reference precision buffers were used. The measured pH values differed distinctly from calculated pH values in the acidic and alkaline parts of the pH interval investigated (6.57-8.15). Measurements of actual pH with proper calibration standards therefore seem mandatory.

Bicarbonates↗
PubMed1989

Carbon dioxide tensions in physiological salt solutions: direct measurements.

Carbon dioxide tensions were measured directly in organ baths and a tonometer aerated in parallel with 6 different gas mixtures of O2 and CO2, 3 gas flows, 3 equilibration periods, and 3 bicarbonate concentrations. The measured partial pressure of carbon dioxide differed systematically from expected values, probably due to errors in the carbon dioxide measurement system. In conclusion, carbon dioxide equilibrates with the bubbling gas in the baths as well as in the tonometer to an almost perfect equilibration.

Bicarbonates↗
PubMed1989

Bootstrap investigation of the stability of a Cox regression model.

We describe a bootstrap investigation of the stability of a Cox proportional hazards regression model resulting from the analysis of a clinical trial of azathioprine versus placebo in patients with primary biliary cirrhosis. We have considered stability to refer both to the choice of variables included in the model and, more importantly, to the predictive ability of the model. In stepwise Cox regression analyses of 100 bootstrap samples using 17 candidate variables, the most frequently selected variables were those selected in the original analysis, and no other important variable was identified. Thus there was no reason to doubt the model obtained in the original analysis. For each patient in the trial, bootstrap confidence intervals were constructed for the estimated probability of surviving two years. It is shown graphically that these intervals are markedly wider than those obtained from the original model.

Azathioprine↗
PubMed1989

Carbon dioxide distribution in Mapleson A and D systems: an experimental study.

The distribution of CO2 in the Mapleson A and D rebreathing systems was investigated experimentally during controlled ventilation and with the expiratory valve closed during inspiration. Maximal and minimal levels of CO2-concentration obtained from capnograms along the tubing were used to construct "gas profiles". For both systems, high tidal volumes and low fresh gas flows resulted in a high degree of gas separation with a pool of alveolar gas near the expiratory valve, and longitudinal gas mixing was minimal. In this manner fresh gas loss was prevented and fresh gas utilization optimized. The end of the tubing nearest the patient was found to act as a reservoir for alveolar gas in the Mapleson A system and fresh gas in the Mapleson D system. Fresh gas utilization in the Mapleson D system was somewhat less efficient than in the Mapleson A system due to the fresh gas admixture to exhaled alveolar gas in the patient-near end of the tubing during expiration. The replacement of the usual expiratory valve of the Mapleson A system by a valve which is closed during inspiration makes the A system an alternative to the D system for controlled ventilation.

Anesthesia, Closed-Circuit↗
PubMed1989

Analysis of change over time.

A brief introduction is given to methods for analysis of epidemiological data where the exposure variable may change over time. The techniques discussed are related to both classical epidemiological methods for analysing the effect of a fixed, dichotomous exposure variable on a dichotomous response variable and to methods for analysis of life time data. Two examples are presented.

Adult↗
PubMed1989

Simple parametric and nonparametric models for excess and relative mortality.

This paper studies two classes of hazard-rate-based models for the mortality in a group of individuals taking normal life expectancy into account. In a multiplicative hazard model, the estimate for the relative mortality generalises the standardised mortality ratio, and the adequacy of a model with constant relative mortality can be tested using a type of total time on test statistic. In an additive hazard model, continuous-time generalisations of a "corrected" survival curve and a "normal" survival curve are obtained, and the adequacy of a model with constant excess mortality can again be tested using a type of total time on test statistic. A model including both the multiplicative hazard model and the additive hazard model is briefly considered. The use of the models is illustrated on a set of data concerning survival after operation for malignant melanoma.

Biometry↗
PubMed1988

Genetic and environmental influences on premature death in adult adoptees.

To assess genetic and environmental influences on adult mortality, we followed 960 families that included children born during the period 1924 through 1926 who were placed early in life with adoptive parents unrelated to them. We evaluated the risks of dying from all causes or from specific groups of causes between the ages of 16 and 58 years for adoptees with a biologic or adoptive parent who died of the same cause before the age of either 50 or 70. We compared these risks with the adoptees' risk of dying from the same causes between the ages of 16 and 58 when either the biologic or adoptive parents were still alive at the ages of 50 and 70. The death of a biologic parent before the age of 50 resulted in relative risks of death in the adoptees of 1.71 (95 percent confidence interval, 1.14 to 2.57) for all causes, 1.98 (1.25 to 3.12) for natural causes, 5.81 (2.47 to 13.7) for infections, 4.52 (1.32 to 15.4) for cardiovascular and cerebrovascular causes, and 1.19 (0.16 to 8.99) for cancers. The death of an adoptive parent resulted in relative risks of death in the adoptees that were close to unity for all causes, natural causes, and infections, 3.02 (0.72 to 12.8) for vascular causes, and 5.16 (1.20 to 22.2) for cancers. A similar but weaker pattern was observed when either a biologic or adoptive parent died before the age of 70. We conclude that premature death in adults has a strong genetic background--especially death due to infections and vascular causes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Multistate models in survival analysis: a study of nephropathy and mortality in diabetes.

How an analysis of a multistate model for survival data may compare with an ordinary survival analysis is discussed. A study of mortality and incidence of nephropathy in insulin dependent diabetes is used as illustration. Proportional hazards regression models with time-dependent covariates and regression models for relative mortality are used for the transition intensities. Alternative basic time scales are also considered.

Actuarial Analysis↗
PubMed1988

Cystic fibrosis in Denmark 1945 to 1985. An analysis of incidence, mortality and influence of centralized treatment on survival.

The entire population of cystic fibrosis (CF) patients in Denmark diagnosed in the period January 1, 1945, to June 30, 1985, comprised 514 persons of whom 62 were diagnosed at autopsy. Of the remaining 452 patients, 372 were probands and 80 were secondary cases. The effect of a centralized treatment on the prognosis was evaluated using a Cox's regression model. Furthermore an incidence analysis was performed using probands including autopsies. Centralized treatment had a significantly beneficial effect on the prognosis (p = 0.02), the death intensity (hazard rate) being decreased by a factor of 0.60. It was calculated that at present 1 out of 4,760 newborn Danes may be diagnosed as suffering from CF before the age of 15 years, and 3% of the Danish population are heterozygotes for CF.

Adolescent↗