Search PubMed⌕ Search

Biomedical subjects

J E Till

Publications and source records attributed to J E Till.

At least 73 records · Page 4Linked to original sources
PubMed1984

Linear analogue self-assessment of voice quality in laryngeal cancer.

This study evaluated the reliability and sensitivity of laryngeal cancer patients' linear analogue self-assessments (LASA) of voice quality. Thirty patients completed LASA scales for a number of voice-related symptoms and abilities several times during a standard treatment programme. The study design allowed evaluation of the scales' reliability, both early and late in treatment, and sensitivity to the changes expected during irradiation. Another 29 post-treatment patients completed the same scales in interviews separated by several weeks. Results indicate that LASA scores were generally reliable, sensitive to clinical change, yet stable when clinical status is unaltered. Though further demonstrations of the validity of these scales are required, their possible use as outcome measures in future clinical trials comparing treatments for laryngeal cancer is feasible.

Adult↗
PubMed1984

The assessment of values in laryngeal cancer: reliability of measurement methods.

Although quantitative estimates of patients' attitudes toward the relative importance of different aspects of health are of great potential usefulness in medical decision making, there is little information about the stability of such values over time, particularly in patients whose clinical state is changing. To examine these questions, we selected a group of patients with laryngeal cancer undergoing treatment with radiotherapy. In this group of patients clinical problems are relatively circumscribed and related to the voice, and a temporary deterioration in voice-related symptoms and abilities is expected during treatment. Thirty patients were interviewed at the start and completion of a month's course of treatment. At each interview patients rated the quality of their own voices using a number of visual analogue scales and also provided both holistic and decomposed quantitative values for the importance of different aspects of voice function and sound. Although the analogue scales demonstrated the anticipated deterioration in the quality of the patients' voices, these changes in clinical state were not accompanied by any changes in the values the patients assigned to each aspect of voice sound and function. These results indicate that at least in the short term the values expressed by patients appear to be stable and uninfluenced by changes in their own clinical state. Longer term studies involving more systemic illnesses should now be carried out.

Adult↗
PubMed1984

Do patients and physicians agree on the assessment of voice quality in laryngeal cancer?

Information is available regarding tumor control rate and survival for patients with cancer of the larynx. Less well known are the effects of treatment upon the patient's quality of voice and way of life because there is at present no suitable method for the routine clinical assessment of these effects. This paper reports some results of the evaluation of one assessment technique using linear analogue scales, and it examines the agreement between patients' and physicians' assessment of severity of voice related function and sound. Each of 20 patients taped a voice recording and subsequently rated his overall functional ability and the sound of his voice. Twenty physicians rated the sound of the 20 patients' voices from the recording and judged functional ability from a written description. Agreement between the scores of patients and physicians indicated that despite being strongly correlated, they were often not the same. Implications of this technique are discussed.

Adult↗
PubMed1984

Describing health states. Methodologic issues in obtaining values for health states.

In health status index construction quantitative values for different states of health are frequently obtained by presenting written descriptions to raters whose values are elicited using one or more methods. In this study the authors examined the influence of several aspects of this measurement process upon the quantitative results obtained. They prepared a set of written descriptions of health states, each state being described in both a standard point-form and a narrative format. The narrative format was written in the first person singular, and listed all symptoms or problems associated with the state, whereas the point-form description included only the most severe symptom or problem. Values for these states were elicited from a group of 64 patients using two commonly employed methods, the standard gamble of Von Neumann and Morgenstern and category rating. The results indicate that the type of scenario presented to the rater and the sequence in which the methods of assessment were used had a major influence on the results. This work indicates that there is a need to examine systematically the process of obtaining quantitative values before reliance can be placed upon the results.

Adult↗
PubMed1983

A stem cell model of human tumor growth: implications for tumor cell clonogenic assays.

A simple stem cell model of human tumor growth is presented. Three tumor cell populations are predicted: stem, transitional, and end cells. The properties of these cells are discussed in terms of their behavior in currently available technologies for investigation of cell kinetics and for their influence on clinical outcome. Stem cell renewal, transitional cell proliferation, and cell loss are analyzed mathematically to define their influence on the relative proportions of cell populations; it is demonstrated that stem cell renewal has a central role in determining the growth properties of tumors. The impact of a stem cell model on the use of tumor clonogenic assays as predictors of clinical outcome is discussed; opinions are expressed as to the definition of reasonable expectations for current experimental procedures.

Antineoplastic Agents↗
PubMed1982

Stem cells in differentiation and neoplasia.

The stem cell concept continues to be very useful both for studies on cellular differentiation and for studies on neoplasia. At present the concept is being enlarged to include consideration of a new aspect: stem cell genetics, at the molecular level. Some questions are still to be answered. What is the basis for genetic regulation of "commitment," that is, the transition from pluripotent stem cells to committed progenitor cells? Does neoplasia involve changes in the genetic material of hemopoietic stem cell? To illustrate the ways in which genetic approaches may be used to provide new answers to these important questions, a minimal model of commitment at the molecular level is presented. The model is based on the assumption that movable genetic elements may play a hitherto-unsuspected role in the early stages of stem cell differentiation. It provides a simple explanation for the apparent close association between loss of potential for stem cell renewal and commitment. The possibility that analogous movable genetic elements may be involved in both the development of neoplastic cells and the differentiation of normal cells is also discussed. The need for caution in interpreting evidence for apparent differences in the genetic material of normal and neoplastic cells is stressed.

Animals↗
PubMed1982

Attitudes toward quality of survival. The concept of "maximal endurable time".

The purpose of this study was to examine attitudes toward the duration of survival in different health states. Health professionals were asked to consider hypothetical situations in which a specified period of time would be spent in a defined health state. Preferences for these different situations were assessed using two methods--a Preference Questionnaire and a Certainty Equivalence method. The results obtained indicated that attitudes toward duration of survival depended strongly on the amount of time to be spent in a hypothetical health state, and on the quality of the state. As the duration of survival increased, or the state under consideration became more dysfunctional, a higher proportion of raters expressed a preference for immediate death over further survival in the dysfunctional state. These results contradict the view that time preference curves always increase monotonically, independent of the quality of survival. Instead, subjects appeared to identify a variable, the "maximal endurable time" in a given state. When this time was exceeded, attitudes toward additional increments of survival changed dramatically.

Attitude to Health↗
PubMed1982

The measurement of patients' values in medicine.

The standard gamble, derived from decision theory, is considered a criterion method for obtaining patients' values for different health states. In this method, a rater's value for a health state is obtained by determining, in a hypothetical setting, his readiness to remain in that state or take a risky choice with different outcomes of known value. According to the expected utility criterion, a rater's utility or value for a particular state should not be influenced by changes in the gamble outcomes. The standard gamble was used to obtain 64 patients' judgments of a set of health states, first with the outcomes of perfect health or death, and subsequently with other health states as outcomes. The changes in gamble outcomes significantly influenced reported values for health states, indicating that the standard gamble is internally inconsistent. This observation poses a major limitation to its use as a value measurement method in medicine.

Adult↗
PubMed1982

Measurement of individual preferences. The importance of "situation-specific" variables.

Women in two Ontario cities were asked to express their preferences about a medical decision: A fictitious patient with cancer was to be treated either conservatively without hope of cure, or radically, by a risky treatment having cure or immediate death as possible outcomes. Situation-specific variables were varied systematically across the sample by varying the levels of the fictitious patient's physical and psychosocial health and achievement motivation. The results obtained indicate that individual preferences shift in response to changes in the situation in which the decision is made. These findings raise questions about the uses to be made of measurements of preferences, especially in relation to what is meant by a "best decision."

Adult↗
PubMed1981

An approach to classifying prognostic factors related to survival experience for non-Hodgkin's lymphoma patients: based on a series of 982 patients: 1967-1975.

The survival experience of 982 non-Hodgkin's lymphoma patients registered at Princess Margaret Hospital, Toronto, between 1967 and 1975, was studied. Prognostic groups were obtained by means of a classification procedure based on standard statistical techniques; the variables utilized in the classification were ones of known reproducibility which could be measured with little inconvenience to the patient. The results show that these prognostic groups give better information than the Ann Arbor staging classification in the sense that the survival curves are clearly separated and "good prognosis" and "poor prognosis" groups are clearly identified. Implications for therapy planning are briefly discussed.

Aged↗
PubMed1981

Blast cells in acute myeloblastic leukemia: a model.

A model of the evolution of acute myeloblastic leukemia (AML) as a clonal hemopathy is presented and reviewed in light of the available data on the behavior of leukemic blast-stem cell colonies. The model postulates that determination of a pluripotent stem cell of a leukemic clone occurs abruptly with intermediate stem cell classes being rare. Transformations occurring in committed myelopoietic progenitors are not self-maintaining. Leukemic clones in AML originate by genetic transformation to a lineage independent of myelopoietic differentiation. The biological behavior of AML clones changes with time as a result, in the short term, of environmental changes, and in the long term, of genetic changes. Sensitivity of leukemic blast colonies to adriamycin and Ara-C, although variable from patient to patient, is relatively stable for one clone during a major portion of the course of the disease.

Animals↗
PubMed1980

The prognostic value of HLA phenotypes in Hodgkin's disease.

Analysis of a group of 79 patients with previously untreated Hodgkin's disease, whose HLA phenotypes were determined in 1972-73, shows that patients in a sub-group with the specificities collectively known as Aw19 have significantly poorer survival than patients without these specificities. The degree to which the serologically-detectable HLA antigens assist in determining the prognosis for survival has been analyzed using multiple regression analysis and retrospective stratification. Both approaches indicate that the association of HLA phenotype with survival is not accounted for by correlations between HLA antigens and other know prognostic factors, such as stage, histology, age, and sex. The greatest prognostic value of Aw19 appears to be for patients with relatively unfavorable age (greater than 40 years), stage (III and IV), or histology (lymphocyte depletion, mixed cellularity).

Adult↗
PubMed1980

The cellular basis of self renewal in culture by human acute myeloblastic leukemia blast cell progenitors.

Blast cells from patients with Acute Myeloblastic Leukemia (AML) were separated according to cell size using velocity sedimentation under unit gravity. Fractions obtained in this way were plated in methyl cellulose with a growth stimulator present in media conditioned by leukocytes in the presence of phytohemagglutinin (PHA-LCM). Colonies of blast cells form under these conditions. Pooled cell suspensions from such colonies were plated in microwells; the plating efficiency of such suspensions is a measure of blast progenitor self-renewal occurring in the original blast colonies. Self-renewal assays on each fraction indicated that self renewal among blast progenitors is heterogeneously distributed with subpopulations differing in renewal capacities. The results are consistent with the view that blast cell subpopulations in AML undergo a series of transitions associated with decreasing self renewal capacity, analogous to that observed in normal hemopoiesis, where proliferative capacity decreases with increasing differentiation.

Cell Count↗
PubMed1980

Null results in clinical trials: the need for a decision-theory approach.

A framework is developed to take explicitly into account the conflicting demands of ethics and scientific rigor in the design of clinical trials. The framework recognizes the part played by the clinical-scientific community in the weighing of a new result provided by a clinical trial. To illustrate the usefulness of the framework, a value system is adopted which gives relatively high weight to ethical considerations. The analysis based on this value system reveals some limitations of the present clinical-trials mechanism, especially if success is defined exclusively in terms of cure, and other dimensions of the health system, such as explanatory, care, cost or prevention variables are neglected. On the basis of this analysis, it is suggested that: (a) If randomized clinical trials are to be ethically acceptable, they will necessarily yield a large proportion of null results. (b) Positive results from ethically acceptable clinical trials would be expected to have less impact than null results; unless this is the case, there will be a tendency to encourage false hopes. (c) Trials need not yield entirely null results, provided that attention is not focused exclusively on a single outcome variable. A trial of chemotherapy for acute myeloid leukaemia in adults is used to illustrate the need for new approaches to the planning and design of clinical trials.

Adult↗
PubMed1980

Focus-forming ability and surface markers of hamster-human malignant lymphoma hybrids.

We have examined the properties of hybrid cells formed by polyethylene glycol-mediated fusion of the GRC+L-73 line of Chinese hamster ovary (CHO) cells with peripheral blood cells from patients with chronic lymphocytic leukemia (CLL) or with bone marrow cells from patients with malignant lymphoma. The results indicate that hybrid cells can be detected by their ability to form "foci" of characteristic morphology in the presence of a monolayer of parental CHO cells and that clones isolated from such foci express aspects of the differentiation status, as detected by immunologic markers, of the human parental cells.

Animals↗