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PubMed1996

An expert system based on causal knowledge: validation on post-cardiosurgical patients.

A new expert system for the analysis of post-cardiosurgical patients in Intensive Care Units is described, and a preliminary validation performed. The inference engine employs a hybrid reasoning method which integrates quantitative and qualitative simulation techniques in an original manner. The long-term knowledge consists of a causal network which reproduces the main relationships between physiological quantities involved in the course after cardiac surgery. Emphasis has been given to respiratory and metabolic, as well as cardiovascular quantities both in the systemic and pulmonary circulations. Preliminary system validation has been performed on a set of 40 cardiosurgical patients, previously classified either at normal-risk (17 patients) or at high-risk (23 patients) by means of statistical classification techniques. In most cases, predictions of the expert system substantially agree with those provided by the more traditional statistical method. The system, however, is also able to furnish detailed explanations on the possible physiological causes responsible for the patient status. In particular, simulation results indicate that a reduction in the cardiac index (19 cases) and an increase in the oxygen utilization coefficient (19 cases) are the most critical alterations in the high-risk patients. The system imputes the reduced cardiac index to a rise in total systemic resistance (15 high-risk patients), a decrease in cardiac strength (2 high-risk patients) or an insufficient filling volume of the systemic circulation (4 high-risk patients). Furthermore, in 6 high-risk patients the depressed cardiac outflow occurs with a reduction in the arterial oxygen content, mainly imputable to an insufficiency of blood hemoglobin content. Finally, two examples of the complete expert system explanatory capabilities are shown with reference to a pair of high-risk patients and discussed.

Blood Circulation↗

PubMed1983

The surgeon general's "epidemiologic criteria for causality." A critique.

The methodology of the 1982 Report of the Surgeon General is examined with special reference to smoking and lung cancer. Part II of the Report describes the five criteria for causality that have guided the judgment of committees since 1964. I show that not one of the criteria, plausibly interpreted, is satisfied by the epidemiologic evidence for lung cancer. A weakness underlying all the Reports is a prior failure to recognize all the logical possibilities inherent in an association between smoking and a disease. The five criteria and the subjective method of "judgment" are inappropriate to a scientific analysis; they should be replaced by the objective testing of hypotheses. Limitations in the evidence and in concepts about tobacco carcinogenesis preclude definitive conclusions. Nevertheless, the entire association between cigarette smoking and lung cancer--at least in male Caucasoid populations--is unlikely to be explained by causation.

Adult↗

PubMed1983

The surgeon general's "epidemiologic criteria for causality": a criticism of Burch's critique.

In this paper, it has not been possible to critically and objectively assess each of the points made by Burch, since it would be time-consuming both for this author as well as for the reader. However, the major areas of concern expressed by Burch have been reviewed and evaluated. This has in many instances required going back to the original reports of studies to which Burch refers. In doing so, it came as a complete surprise to note that Burch has incompletely presented the findings of several studies or has omitted discussing others more fully. This is, needless to say, most disturbing. In viewing the issue of the causal interpretation of the cigarette smoking--lung cancer relationship, it would appear that Burch would not be satisfied unless there is a randomized controlled experiment in humans. However, since such an experiment seems hardly feasible, one must depend upon a synthesis of findings of epidemiologic observations, experimental work on animals and studies of chemical constituents of tobacco and cigarette smoke. However, these do not seem to satisfy Burch, who has developed a theoretical conceptual framework for the etiology of cancer and many other diseases, based upon statistical models and equations. Such an approach is extremely limited. Scientific information and inferences are in the public domain, thereby allowing criticism and evaluation. It is customary, in the experimental sciences, for a scientist who is dissatisfied with the findings of another scientist, to attempt to repeat the experiment to see if his findings are the same or different. This should also be expected in the cigarette smoking-lung cancer issue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Metamemory, memory performance, and causal attributions in gifted and average children.

Fifth and seventh graders who had been teacher-selected as high- or average-achieving were tested on the Kognitiver Fähigkeits Test, a standardized test of intellectual abilities for German children. Children who met preestablished criteria as gifted or average were then tested on measures of metacognitive knowledge, attributional beliefs, and performance on a sort recall task. Results indicated ability-related differences in metamemory and sort recall performances. Responses to the attributional questionnaires also varied systematically according to ability: gifted children were more likely to attribute their academic successes to high ability than were average children, who showed a stronger belief in the importance of effort in determining task outcomes. Causal modeling analyses illustrated the strength of metacognitive knowledge as a performance predictor on the memory task, especially for average children. Results are discussed in terms of the value of metacognitive theory in understanding individual performance differences.

Achievement↗

PubMed1994

Can we predict solar ultraviolet radiation as the causal event in human tumours by analysing the mutation spectra of the p53 gene?

The tumour suppressor gene, p53, has proved to be one of the genes most often modified in human cancers. These alterations consist mainly of point mutations located in the evolutionarily conserved sequences which render the protein inactive for its normal biological functions. In fact the p53 gene presents nearly 300 potential mutation sites whose analysis should enable the correlation of specific mutation spectra with different causal agents in cancer development. In this study we have analysed the mutation spectrum of the p53 gene in skin tumours from normal individuals and repair-deficient xeroderma pigmentosum (XP) patients in comparison with mutations found in internal cancers. Point mutations are mainly GC-->AT transitions in skin tumours (74% in non-XP, 87% in XP), and also to a lesser extent in internal tumours (47%) where, however, they are mainly located at CpG (63%) sequences probably due to the deamination of the unstable 5-MeC. Moreover, mutations are targeted at py-py sequences in over 90% of skin tumours whereas the distribution of mutations in internal malignancies is proportional to the frequency of py-py sites (61%) and other sequences (39%) at mutable sites. Indeed, in XP skin tumours 100% of the mutations are targeted at py-py sequences and 55% of these are tandem CC-->TT transitions considered as a signature of UV-induced lesions. In skin tumours from normal individuals, 14% of the p53 mutations are double mutations and as in XP skin tumours all these are CC-->TT transitions. In contrast, internal tumours rarely contain tandem mutations (0.8%), and of these only 2/14 were CC-->TT transitions. Finally, nearly all (95%) of the mutations in XP are located on the non-transcribed strand while internal or non-XP skin tumours do not show this strand bias. Hence, the mutation spectrum analysed in XP skin tumours also demonstrates for the first time the existence of preferential repair in humans. In conclusion, the specificity of UV-induced p53 mutation spectra in skin tumours shows that this gene is a particularly appropriate candidate for the correlation of mutation spectra with specific damaging agents.

DNA↗

PubMed1986

The role of carpal instability in scaphoid nonunion: casual or causal?

We studied twenty consecutive scaphoid nonunions in twenty patients between the ages of eighteen and thirty-eight years. There were nineteen males and one female. The mean age was 25.2 years. Factors evaluated were fracture displacement, delay in treatment, and carpal instability. Fracture displacement and carpal instability were documented in patients by abnormal x-rays showing fragment displacement, abnormal scapholunate and radiolunate angles, etc., or by fluoroscopically controlled arthrography. We concluded that intercarpal ligamentous instability is consistently present and, therefore, the critical factor in wrists with ununited scaphoid fractures. Thirteen patients have been treated surgically; ligamentous disruption was confirmed at surgical exploration. In twelve patients, treatment of the nonunion included intercarpal ligamentous reconstruction. A satisfactory outcome was achieved in all twelve of these patients. One patient's treatment did not include ligament reconstruction. Although the scaphoid fracture united after a Russe bone graft, he remains symptomatic with persistent intercarpal instability. The remaining seven patients are being evaluated or awaiting surgery. Since ligamentous injury is so common in nonunion, we believe it is causal and that surgical care of nonunion involves ligamentous repair or other stabilization procedure. Prevention of nonunion involves early attention to the therapy of carpal instability when associated with scaphoid fracture.

Adolescent↗

PubMed1992

A review of the likely causal pathways relating the reduced density of breeding dippers Cinclus cinclus to the acidification of upland streams.

Previous work has shown that the breeding density of a bird characteristic of upland streams, the dipper Cinclus cinclus, is markedly reduced at low pH in both Wales and Scotland. Populations also declined when streams became more acidic. Evidence of causal explanation for these relationships is that: (1) Food quantity is reduced in acidic streams, and important prey, including those rich in calcium, are scarce; (2) Blood chemistry in pre-breeding birds differs between acid and circumneutral streams, with plasma calcium reduced in those breeding at low pH. Skeletal sources of calcium are probably limited; (3) The time spent foraging by pre-breeding birds on acidic streams is markedly increased, even though overall energy costs on acidic and circumneutral streams are similar. Body condition is inferior to birds on circumneutral streams; (4) Egg laying is significantly delayed on acidic streams irrespective of an effect on laying of altitude, and clutch and brood sizes are significantly reduced; (5) Eggs are lighter and shells thinner at low pH; (6) Chick growth is reduced at low pH; (7) Contamination by heavy metals and persistent organochlorines is low in the populations on acidic streams and cannot explain the impaired breeding performance. None of these features can exclude the possibilities that acidic streams either hold populations of poor quality birds, which show the above features, or that acidity affects the breeding ecology of all dippers that attempt to breed at low pH. The qualitative outcome of these two alternatives is identical.

Journal Article↗

PubMed1984

Chronic kidney disease and organic chemical exposures: evaluations of causal relationships in humans and experimental animals.

Chronic renal failure is a serious health problem in the United States and other developed countries, and large amounts of public funds are being expended for what is essentially palliative treatment of this disease. Historical data also indicate increasing trends for urinary tract cancers of both sexes in the United States. Although the data on humans are not definitive, causal associations appear to exist between occupational exposures to some hydrocarbon solvents and chronic kidney disease, and there is preliminary evidence that suggests an association between organic chemical exposures and cancers of the urinary tract in humans. A review of more than 230 chemicals tested in two-year chronic toxicity studies by the National Toxicology Program (NTP)/National Cancer Institute (NCI) has identified two chemical classes that commonly produced nonneoplastic chronic renal disease in rodents: aromatic amines and organohalides. Tumors of the kidney were most frequently produced by alkyl or alkenyl halide compounds, while tumors of the bladder were caused by aromatic amines. Consistent with many literature reports, short-chain halogenated hydrocarbons appeared to have a propensity for causing a low incidence of renal tubular carcinoma in exposed rodents. Comparative analyses of the NTP/NCI studies did not indicate consistent sex or species differences in the nonneoplastic chronic toxic response, but chemically induced urinary tract cancers occurred more commonly in rats than in mice, and chemically induced cancers of the kidney occurred more commonly in males than in females. Viewed collectively, these data indicate a potential for organic chemicals, especially halogenated hydrocarbons and aromatic amines, to produce chronic kidney injury in humans and other mammalian species.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Infant mortality in Sri Lankan households: a causal model.

The infant mortality rate in Sri Lanka has fallen precipitiously since World War II, to 44 per 1000 births, a rate that is similar to a number of Western Countries. Yet the aggregated country rate masks wide variations across districts, from a low 21 per 1000 in Jaffna District to a high of 100 per 1000 in Nuwara Eliya District. Such regional variations in infant mortality rates have been shown to be related to a number of social, demographic and intitutional characteristics of each area. To specify such linkages we move, in this paper, from the aggregate level of analysis to the level of individual households in order to look for social, economic and other characteristics associated with infant deaths. Data are derived from a systematic interview of 480 household heads in 12 villages of Sri Lanka, collected in 1980. The most proximate factors, public health or medical variables, that predict infant death in particular households include quality of family nutrition, supervised childbirth, immunization of children and, most significant, whether the family has a sanitary latrine. Yet these medical variables are strongly associated with educational and economic characteristics of the family which, in turn, are predictive of infant mortality. Poor families and poorly educated mothers are less likely to go to hospital for childbirth, have a latrine, etc., and more likely to have had an infant die. Underlying the variations in education and economic status are variations in ethnic group; families with poor sanitation, least education and few economic resources are most likely to be members of the minority communities, Ceylon or Indian Tamils and Muslims. Minority group membership is significantly associated with infant mortality as well. When a set of medical, educational, economic and cultural variables are examined simultaneously within a path model we show that the best causal explanation of infant death in Sri Lankan households says, "Minority group status results in poverty which prevents families from having safe sanitary facilities which causes infant death". Infant mortality in Sri Lanka is thus not simply a medical problem to be dealt with by public health programs, nor is it solely an economic problem that can be solved with creation of jobs, but it is better seen as a problem of the structure of the whole society.

Adult↗

PubMed1989

Three conflicts as a result of causal attributions.

There is a difference between the causal attributions of cancer (Ca)-patients and those of myocardial infarction (MI)-patients. MI-patients go through and check their autobiographies looking for the possible causes suggested by the medical world. Ca-patients on the contrary search for possible explanations. This is probably due to the lack of medical knowledge on the cause and course of their disease. They search through their autobiographies and the result is idiosyncratic, very personal attributions with which they create an explanation which is often not in accordance with the physicians' view. These attributions of Ca-patients are a source of conflicts, both within themselves (doubt), with their physicians and with their partners or other close relatives. Nevertheless they stick to their own explanations, although often secretly and with ambivalence, and despite the conflicts which they produce.

Myocardial Infarction↗

PubMed1996

Promoting the organ donor card: a causal model of persuasion effects.

Due to the present critical shortage of donor organs available for transplantation, effective communication strategies are necessary to heighten public commitment to donation. The promotion of organ donor card-signing may be a successful vehicle in the achievement of this goal. Based on the Elaboration Likelihood Model of persuasion effects, evidence of the motivation for organ donor card-signing, and examination of previous donation message tests, this study proposes and tests a causal model of response to organ donor card appeals. The inter-relationship of values, empathy arousal, and issue involvement was found to be a significant driving force in the persuasive process for the behavioral intention to sign an organ donor card. Implications of these findings for future research are addressed.

Adolescent↗

PubMed1980

Extent of skin tumour initiation in mice by 7,12-dimethylbenz[alpha]anthracene and induction of arylhydrocarbon monooxygenase are not causally related.

In order to clarify further the relation between extent of arylhydrocarbon monooxygenase (AHM) induction and tumour initiation by polycyclic aromatic hydrocarbons, AHM activity and concentration of 7,12-dimethyl-benz[alpha]anthracene (DMBA) equivalents in dorsal epidermis were determined after both intragastric and topical administration of DMBA. Although in each case the dose applied caused comparable tumor incidences, both the extent of AHM induction and the concentration of DMBA equivalents were remarkably different: while topically applied DMBA stimulated AHM several-fold, intragastric instillation led to only a slight increase, if any. The concentration of DMBA equivalents in epidermis was about 100-fold higher after topical DMBA application than after intragastric administration. These data provide further evidence that extent of tumour initiation by DMBA and of AHM induction are not causally related; positive correlations found in certain cases appear to be fortuitous. Induction of AHM seems to be rather a function of DMBA concentration adjustment in epidermis and to indicate, if anything, elevated detoxification.

Administration, Oral↗

PubMed1989

Could Borrelia burgdorferi be a causal agent of sarcoidosis?

Sarcoidosis is a multisystem granulomatous disorder of unknown etiology, most commonly affecting young adults presenting most frequently with bilateral hilar lymphadenopathy, pulmonary infiltrations, skin or eye lesions (1). Borrelia burgdorferi, the causal agent of Lyme disease, could also be responsible for sarcoidosis. Domestic animals may play a major role in transmitting the disease to humans. The modes of transmission to such animals and possible contact transmission to humans are still obscure and should be more fully investigated. Small rodents have been found to play a role as reservoirs for Borrelia burgdorferi. They are suspected to constitute an important source of contamination for domestic animals. The author explains in this paper how geographic distribution and familial occurrence of sarcoidosis as well as racial differences in the incidence of this disease, could be related to such findings.

Animals↗

PubMed1981

Attributions of causality for drinking behavior made by alcoholics and by normal drinkers.

Alcoholic individuals often are assumed to deny personal responsibility for their alcholism and to assign causation to external situational factors. To evaluate this assumption, 20 alchololics and 14 nonalcoholics made causal attributions for a recent personal drinking episode and for the drinking behavior of three target individuals (an abstinent alcoholic, a nonabstinent alcololic, and a nonalcoholic). Results showed that both alcoholic and non-alcoholic subjects tended to make external attributions for their own drinking behavior. Subjects' attributons for the target individuals depended on bot the targest' and subjects' drinking histories. The results are discussed in terms of their relevance to models of alcoholism and to actor-observer differences in casual attribution processes.

Alcohol Drinking↗

PubMed1994

Behavior in cocaine-exposed infants and children: association versus causality.

The effects of prenatal cocaine exposure on infant and child development and behavior are uncertain. This ambiguity has been enhanced by the early nature of human research and suboptimal study designs. Methodological difficulty in this research, particularly in the consideration of confounding effects, has made it difficult to ascribe causal relationships. Future research must consider more precise measures of confounding.

Child Behavior Disorders↗

PubMed1992

Refinement of diagnostic assays for a probable causal mutation for porcine and human malignant hyperthermia.

The substitutions of T for C1843 in the porcine ryanodine receptor (RYR1) gene, which deletes a HinPI restriction endonuclease site and creates a HgiAI site, and of T for C1840 in human RYR1, which deletes a RsaI site, lead to Cys for Arg substitutions in the ryanodine receptors and are probable causal mutations for malignant hyperthermia (MH). To improve the restriction endonuclease assay of these sites, thereby providing an accurate, reliable diagnosis for MH, introns flanking the exon containing the mutation were sequenced, permitting identification and PCR amplification of a 659-bp porcine gene sequence that contains both constant and variant HgiAI sites and a 922-bp human gene sequence that contains both constant and variant RsaI sites. As a result, these PCR-amplified sequences contain constant internal controls for the reliable differentiation by restriction endonuclease digestion of normal, heterozygous, and MH genotypes.

Animals↗

PubMed1995

Causal inference from indirect experiments.

An indirect experiment is a study in which randomized control is replaced by randomized encouragement, that is, subjects are encouraged, rather than forced, to receive a given treatment program. The purpose of this paper is to bring to the attention of experimental researchers simple mathematical results that enable us to assess, from indirect experiments, the strength with which causal influences operate among variables of interest. The results reveal that despite the laxity of the encouraging instrument, data from indirect experimentation can yield significant and sometimes accurate information on the impact of a program on the population as a whole, as well as on the particular individuals who participated in the program.

Humans↗

PubMed1994

Causal and emotional factors related to work stress in ICU nursing staff. The importance of accurate measurement.

This study was designed to determine the degree of intervention of causal and emotional factors in work stress in intensive care unit (ICU) nursing staff. A questionnaire to assess stress causes (27) and associated emotions (33) was given to 123 people (85 registered nurses and 38 auxiliary nurses) aged 22-56, working in ICUs in different hospitals in Palma de Mallorca. Descriptive and factorial analyses were carried out. Respondents gave most stress causes a medium score (3.5-6.5 points), the highest values corresponding to staff shortage (mean = 6.71), bad management organisation (mean = 6.65) and little free time (mean = 6.5). These causes are grouped in seven factors which account for 65.51% of variance and are particularly related to organisational problems, training and personal relationships, work demands and physical and emotional overload. The most important emotions for this sample are: responsibility (mean = 6.61), impotence (mean = 6.23) and desire to excel (mean = 6.080). Such emotions are divided into seven factors which explain 65.31% of the variance and define states of personal satisfaction, depersonalisation, anxiety, low self-esteem, helplessness and arrogance. Surprisingly, the main factor with the value 5.08 and a variance of 15.42%, corresponds to positive or pleasant emotions. The results corroborate previous research findings on work stress, provide a simplified tool for assessing this and show the need to quantify the degree of such manifestations in the assessments.

Adult↗