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Biomedical subjects

N F Boyd

Publications and source records attributed to N F Boyd.

At least 109 records · Page 6Linked to original sources
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

The development of a method for assessing the quality of life of cancer patients.

Although the need for a method of measuring the quality of life of patients undergoing therapy for cancer has been widely recognised, no adequately evaluated or feasible method has been established. We describe a method in which 31 items were assessed by patient self report using linear analogue scales. Eighteen items inquiring about general health problems were derived from the Sickness Impact Profile, an established method of assessing the effect of health upon behaviour and function. Thirteen items inquiring about major problems associated with breast cancer were derived from clinical experience and the opinions of patients with this disease. Each item of the measurement method (instrument) has been evaluated for content, feasibility, reliability and validity by methods that are widely used in psychometry but less familiar in medicine. It appeared easy to use, acceptable and reliable in these assessment. Validity was evaluated indirectly since no standard measurements of quality of life exist for comparison. Most items appeared valid when compared to alternative measurement methods including the Sickness Impact Profile and evaluation by a physician in a structured interview. The correlations between items in the instrument were analysed by factor analysis and seemed to fit with the clinical features of breast cancer. The method distinguished between clinically distinct groups of patients and detected changes with time. The study illustrates the possible approaches to the scientific evaluation of methods for measuring subjective features of patients lives. This method appears suitable for some purposes to measure quality of life in breast cancer and is intended to be flexible enough to be modified for other diseases. However, further evaluation, development and refinement will be needed before routine clinical application can be recommended.

Attitude to Health↗
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

Mammographic patterns and breast cancer risk: methodologic standards and contradictory results.

The claim that classification of the pattern of the breast parenchyma upon mammography can distinguish groups at different risks for breast cancer has been examined by 17 other studies published in the English language literature with contradictory results; this controversy was assessed by us in examination of these studies for their adherence to commonly accepted methodologic standards for the investigation of causal relationships. The nine standards for the examination of the studies included a description of the way the study population had been assembled and followed up and descriptions of the methods of mammographic pattern classification and breast cancer risk analysis. A strong association was found between the standards adopted by a study and the obtained results. Among nine cohort and case-control studies that found a statistically significant association between mammographic pattern and breast cancer risk, all met at least four standards, whereas only two of six "negative" cohort or case-control studies met as many as four standards. Among prevalence surveys, the association between methods and results was less striking, but several negative prevalence surveys were associated with "positive" cohort studies employing the same group of patients. These results indicate that methodologic differences among studies contribute substantially to the controversy surrounding this subject. Studies that follow the usual scientific methods employed in the epidemiologic investigation of risk generally have confirmed an association between mammographic pattern and breast cancer risk.

Age Factors↗
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

Measurement of values for states of health with linear analog scales.

Medical decisions may be greatly influenced by the values that patients place on different states of health. Previous attempts to obtain quantitative estimates of such values have assumed the numerical values assigned to different levels of health will remain constant regardless of the context in which the measurement is made. To examine this assumption, 64 ambulatory patients ranked five scenarios describing different states of health in order of preference. One of the scenarios was ranked as worse than death by 22 percent of raters, and two scenarios were ranked as worse than death by 31 percent of raters. The states were then rated using linear analog scales, first with the anchors or endpoints of perfect health and death, then with the anchor of perfect health replaced by each of the other health states, in descending order of preference, and finally with the anchor of death replaced by each of the other health states, in ascending order of preference. The numerical values assigned to scenarios were substantially and systematically influenced by the anchors on the scale. Relative to the values assigned to health states when anchors of perfect health and death were employed, the same states were assigned systematically higher values when the anchor of death was replaced by other health states, and systematically lower values when the anchor of perfect health was replaced. These findings persisted when states considered worse than death were excluded from the rating process. These results indicate that the quantitative values assigned health states are strongly influenced by the context in which the measurement is made, and that health cannot be regarded as a continuum with death as its lower boundary.

Analysis of Variance↗
PubMed1982

Observer variation in the assessment of patients with rectal cancer.

To examine the reliability of clinical features as possible components of a clinical method of prognostic staging for patients with rectal cancer, the results obtained when two pairs of physicians interviewed and examined a consecutive series of 60 patients with unresected rectal cancer were compared. High levels of agreement between physicians were found for most items of the patient's history, on whether the lesion was palpable, on the distance of the tumor from the anus, on the location and circumferential extent of the tumor, and on whether the tumor was fixed or mobile. Although physicians elicited similar physical signs, their use of terms to describe the rectal lesions varied widely unless agreed-upon criteria were used. There was 63 per cent agreement on the use of descriptive terms among physicians using criteria and only 13 per cent agreement among physicians not using criteria. These results show that prognostically important clinical features in patients with rectal cancer can be reliably identified and are thus suitable for inclusion in methods of clinical prognostic staging for this disease.

Humans↗
PubMed1982

Bias and the association of mammographic parenchymal patterns with breast cancer.

We have carried out a case-control study to evaluate the association between Wolfe's mammographic patterns and the risk of breast cancer, and to examine the influence of control selection and the radiologist who read the films upon the results obtained. Mammograms of the non-cancerous breast of 183 women with unilateral breast cancer were compared with mammograms from two age-matched control groups: a group of asymptomatic women attending a screening centre, and a group of symptomatic women referred for the diagnostic evaluation of suspected breast disease. Films were arranged in random sequence and independently classified by 3 radiologists. A strong and statistically significant association was found between mammographic dysplasia and breast cancer when controls from the screening centre were compared to cases, but not when cases were compared to women referred for the diagnostic evaluation of breast disease. This result appears to arise in part because of an association between symptoms of benign breast disease and mammographic dysplasia, and suggests that some previous negative studies of the association of mammographic patterns with breast cancer may have arisen from the inclusion of symptomatic subjects as controls.

Adult↗
PubMed1982

Mammographic signs as risk factors for breast cancer.

We have carried out a case-control study to examine the relationship between mammographic signs and breast cancer. The mammographic signs assessed were prominent ducts and dysplasia. The cases were a group of 183 women with histologically verified unilateral breast cancer. The controls were a group of women attending a screening centre. Cases and controls were individually age-matched. Mammograms from the non-cancerous breast of the cases were randomly assembled with those of the controls and classified by 3 radiologists without knowledge of which films were from cases and which from controls. Mammographic dysplasia was found to be strongly associated with breast cancer, particularly in women aged less than 50. Prominent ducts were only weakly associated with breast cancer. Multivariate analysis showed that the association between dysplasia and breast cancer could not be explained on the basis of other risk factors for breast cancer, and that classification of dysplasia discriminated more strongly between cases and controls than did classification of Wolfe's mammographic patterns. These results show that mammograms contain information about risk of breast cancer. Mammographic dysplasia is strongly associated with breast cancer, is present in a substantial proportion of patients with the disease, and may offer opportunities for prevention.

Adult↗
PubMed1982

Mammographic patterns and bias in breast cancer detection.

Wolfe's finding that some mammographic patterns (P2 and DY) are associated with an increased risk of breast cancer has been challenged by some authors who suggest that this is due to denser patterns concealing cancers present on the first examination: these cancers, it is argued, are diagnosed in later years, creating the spurious impression of increased cancer incidence. The authors examined this hypothesis in a series of patients with breast cancer but failed to find any evidence that the diagnosis was subject to systematic delay in patients with the P2 or DY pattern. Moreover, studies of a hypothetical model showed that bias in the detection of breast cancer was unlikely to account for more than a small increase in apparent cancer incidence. Thus it appears unlikely that such a bias is responsible for the risk of breast cancer observed in patients with these mammographic patterns.

Adult↗
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

Observer variation in the interpretation of xeromammograms.

We have examined variation in the interpretation of xeromammograms among radiologists designated to take part in a Canadian multicenter randomized controlled trial of screening for breast cancer. Radiologists read 100 xeromammograms comprising 10 histologically proved cancers, 40 benign abnormalities, and 50 normal films. Radiologists' opinions differed widely on the frequency of suspected or identified cancer. The diagnostic category "suspicion of cancer" or "cancer" was selected by radiologists for 10-55% of the films, and biopsy or aspiration was recommended for 21 to 53% of patients whose films were examined. Agreement on specific diagnostic categories was greatest for the diagnosis of cancer; agreement was least for the diagnosis of benign abnormalities and intermediate for the diagnosis of normality. Known cancers were in general correctly identified. These results indicate a need for development of methods to reduce observer variation in a interpretation of xeromammograms while preserving diagnostic sensitivity and validity. Results also emphasize the importance of developing strategies to ensure quality control in multicenter trials.

Breast Neoplasms↗
PubMed1981

Clinical estimation of the growth rate of breast cancer.

To test the ability of the patient's history to provide prognostically important information in breast cancer the authors used information prospectively collected by interview from 756 patients enrolled in a randomized controlled trial of adjuvant therapy. Classification of this information according to the principles of rate of growth created groups with substantial and statistically significant differences in survival. The survival differences created by classifying growth rate were comparable to those created by other prognostic factors, and independent of those created by stage, lymph node status or tumor grade. The patient's history in breast cancer is capable of providing reproducible prognostic information when it is suitable classified, and this information represents a useful addition to current methods of estimating prognosis in breast cancer.

Adult↗
PubMed1981

Prospective evaluation of physical examination of the breast.

The reliability of physical examination of the breast was evaluated by determining the extent of agreement among four experienced breast surgeons who examined the same 100 patients. The consequences of disagreements among surgeons were assessed by determining the diagnostic accuracy of each examiner. Despite differences in the frequency with which each surgeon found abnormalities or masses, or recommended mammography or biopsy, the diagnostic accuracy of the surgeons was very similar, and most disagreements concerned the findings in patients who did not have breast cancer. Breast examination carried out by more than one surgeon may reduce the frequency with which biopsy is performed in patients who do not have breast cancer.

Biopsy↗
PubMed1981

Body weight and prognosis in breast cancer.

We have examined the relationship between risk factors for breast cancer incidence and the subsequent prognosis of breast cancer among patients in a randomized controlled trial of adjuvant ovarian ablation. Body weight was the only risk factor found to be associated with statistically significant differences in survival. This finding could not be explained by a disproportionate number of anatomically more advanced tumors in the heavier women. In premenopausal women aged 45 years or more, the only group to benefit from adjuvant ovarian ablation, there was an interaction of treatment and weight, suggesting that weight exerts its influence on prognosis by a hormonal mechanism. The prognostic effect of weight was generally most marked in patients with tumors whose prognostic characteristics were favorable, and in these patients weight loss as an adjuvant treatment may reduce the frequency of disease recurrence.

Adult↗