Etiologic study vis-à-vis intervention study

Understanding of the logic-dictated essence of the etiologic study, and similarly that of the intervention-study, in the advancement of the knowledge-base of medicine, remains incomplete. Viewing experimental intervention-studies ('clinical trials') as paradigmatic for etiologic studies-necessarily non-experimental-has been wrongheaded. This misunderstanding continues to impede understanding of the essence of what logic dictates to be the etiologic study, adduced decades ago but still commonly confused with the essence of the (seriously malformed) 'case-control' study. Correct understanding of the essence of the etiologic study would pave the way to improved understanding of the intervention study, notably as to how prognostic probability functions could be derived from the data now routinely produced in clinical trials. This paradigm reversal, too, has been previously proposed, but its understanding has remained fogged by wanting understanding of the etiologic study.

Early lung cancer action project: annual screening using single-slice helical CT

The advent of helical CT imaging held promise for the early diagnosis, and thereby, for enhanced curability of lung cancer--a highly fatal disease. In 1993, the Early Lung Cancer Action Project (ELCAP) was initiated and experimentally screened a cohort of 1,000 high-risk persons. Here we summarize the results of the baseline and annual repeat CT screening of these 1,000 subjects. CT-based screening (compared to traditional radiology) was clearly shown to enhance the detection of lung cancer at earlier and more curable stages. A discussion follows of the meaning of the results and possible future screening protocols.

CT screening for lung cancer: coping with nihilistic recommendations

The practicing radiologist today is well persuaded that earlier diagnosis of lung cancer can be achieved with traditional-type radiography and especially with modern computed tomography. The practitioner also is confident that intervention in the context of earlier diagnosis is more effective in preventing death due to this otherwise fatal disease. The practitioner is thus inclined to consider such screening in a high-risk person with suitably long life expectancy, especially when asked to provide it. On the other hand, the practitioner is aware of official recommendations against lung cancer screening, said to be based on demonstrated lack of effectiveness of traditional radiographic screening. Some researchers have expressed concerns about screening-associated "overdiagnosis." Given this dilemma, the critically thinking practitioner is concerned to understand the foundation of the official nihilism in evidence and reasoning, as she or he suspects that something may be seriously wrong in this. This article is an attempt to help such a practitioner in this effort--an effort that in the end is rewarded by the comforting realization that the nihilistic recommendations and hesitation-provoking cautions are founded on pseudoevidence and specious reasoning.

Early lung cancer action project: a summary of the findings on baseline screening

PURPOSE

The Early Lung Cancer Action Project (ELCAP) is designed to evaluate baseline and annual repeat screening by low radiation dose computed tomography (low-dose CT) in persons at high-risk for lung cancer.

METHODS

Since starting in 1993, the ELCAP has enrolled 1,000 asymptomatic persons, 60 years of age or older, with at least 10 pack-years (1 pack per day for 10 years, or 2 packs per day for 5 years) of cigarette smoking, no prior cancer, and medically fit to undergo thoracic surgery. After a structured interview and informed consent, baseline chest radiographs and low-dose CT were obtained on each subject. The diagnostic work-up of screen-detected noncalcified pulmonary nodules (NCN) was guided by ELCAP recommendations which included short-term high-resolution CT follow-up for the smallest nodules. Baseline

RESULTS

On low-dose CT at baseline compared to chest radiography, NCN were detected three times as commonly (23% versus 7%), malignancies four times as commonly (2.7% versus 0.7%), and stage I malignancies six times as commonly (2.3% versus 0.4%). Of the 27 CT-detected cancers, 96% (26/27) were resectable; 85% (23/27) were stage I, and 83% (19 of the 23 stage I) were not seen on chest radiography. Following the ELCAP recommendations, biopsies were performed on 28 of the 233 subjects with NCN; 27 had a malignant and one a benign NCN. Another three individuals underwent biopsy outside of the ELCAP recommendations; all had benign NCNS: No one had thoracotomy for a benign nodule.

CONCLUSION

Baseline CT screening for lung cancer provides for detecting the disease at earlier and presumably more commonly curable stages in a cost-effective manner.

Early lung cancer action project: initial findings on repeat screenings

BACKGROUND

The Early Lung Cancer Action Project (ELCAP) was designed to evaluate the usefulness of annual computed tomography (CT) screening for lung carcinoma. With the baseline results having been reported previously, the focus of the current study was on the early results of the repeat screenings.

METHODS

A cohort of 1000 high-risk individuals was recruited for baseline and annual repeat CT screening. At last follow-up, a total of 1184 annual repeat screenings had been performed. A positive result from the screening test was defined as newly detected, one to six noncalcified pulmonary nodules with interim growth. The diagnostic workup of the individuals was guided by recommendations supplied by the ELCAP investigators to the collaborating clinicians.

RESULTS

Of the 1184 repeat CT screenings, the test result was positive in 30 (2.5%). In 2 of these 30 cases, the individual died (of an unrelated cause) before diagnostic workup and the nodule(s) resolved in another 12 individuals. In the remaining 16 individuals, the absence of further growth was documented by repeat CT in 8 individuals and further growth was documented in the remaining 8 individuals. All eight individuals with further nodular growth underwent biopsy and malignancy was diagnosed in seven. Six of these seven malignancies were nonsmall cell carcinomas (five of which were Stage IA and one of which was Stage IIIA) and the one small cell carcinoma was found to be of limited stage. The median size dimension of these malignancies was 8 mm. In another two subjects, symptoms prompted the interim diagnosis of lung carcinoma. Neither of these malignancies was nodule-associated but rather were endobronchial; one was a Stage IIB nonsmall cell carcinoma and the other was a small cell carcinoma of limited stage.

CONCLUSIONS

False-positive screening test results are uncommon and usually manageable without biopsy; compared with no screening, such screenings permit diagnosis at substantially earlier and thus more curable stages. Annual repetition of CT screening is sufficient to minimize symptom-prompted interim diagnoses of nodule-associated malignancies.

Early lung cancer action project: initial findings on repeat screenings

BACKGROUND

The Early Lung Cancer Action Project (ELCAP) was designed to evaluate the usefulness of annual computed tomography (CT) screening for lung carcinoma. With the baseline results having been reported previously, the focus of the current study was on the early results of the repeat screenings.

METHODS

A cohort of 1000 high-risk individuals was recruited for baseline and annual repeat CT screening. At last follow-up, a total of 1184 annual repeat screenings had been performed. A positive result from the screening test was defined as newly detected, one to six noncalcified pulmonary nodules with interim growth. The diagnostic workup of the individuals was guided by recommendations supplied by the ELCAP investigators to the collaborating clinicians.

RESULTS

Of the 1184 repeat CT screenings, the test result was positive in 30 (2.5%). In 2 of these 30 cases, the individual died (of an unrelated cause) before diagnostic workup and the nodule(s) resolved in another 12 individuals. In the remaining 16 individuals, the absence of further growth was documented by repeat CT in 8 individuals and further growth was documented in the remaining 8 individuals. All eight individuals with further nodular growth underwent biopsy and malignancy was diagnosed in seven. Six of these seven malignancies were nonsmall cell carcinomas (five of which were Stage IA and one of which was Stage IIIA) and the one small cell carcinoma was found to be of limited stage. The median size dimension of these malignancies was 8 mm. In another two subjects, symptoms prompted the interim diagnosis of lung carcinoma. Neither of these malignancies was nodule-associated but rather were endobronchial; one was a Stage IIB nonsmall cell carcinoma and the other was a small cell carcinoma of limited stage.

CONCLUSIONS

False-positive screening test results are uncommon and usually manageable without biopsy; compared with no screening, such screenings permit diagnosis at substantially earlier and thus more curable stages. Annual repetition of CT screening is sufficient to minimize symptom-prompted interim diagnoses of nodule-associated malignancies.

Screening for lung cancer: do we need randomized trials?

In a scientifically ideal randomized controlled trial (RCT) on the efficacy of screening for lung cancer, screening-detected cases would be allocated to immediate intervention or to no action until symptoms lead to diagnostics. The study would provide for learning about the extent to which earlier interventions (defined by disease stage and stage-conditional tumor size) enhance curability, and also about the distributions of disease stage and stage-conditional tumor size at the time of diagnosis under the particular regimen of screening and its associated diagnostics. Because ethics call for randomization to screening or no screening, this contrast no longer provides for studying the curability function of shared concern for all regimens of screening; it addresses only the overall curability advantage specific to the regimen deployed. The same information that is provided by the scientifically ideal RCT is obtainable from a noncomparative study in which each member of the study cohort is subject to both screening and early intervention, so long as the problem of "overdiagnosis" is avoided by documenting growth before biopsy for cytologic or histologic criteria of malignancy and so long as the outcome of intervention is documented by follow-up. The ethically feasible RCT, in addition to compromising the objects of study, involves validity problems of its own and is less efficient by an order of magnitude.

Screening for lung cancer: can it be cost-effective?

Last year, the Lancet reported on a study concerning a particular, avant-garde regimen of CT-based screening for lung cancer, showing its great superiority relative to the corresponding regimen based on traditional radiography (Lancet 1999;354:99-105). That report was met with great interest in the media, worldwide. It thereby also led to substantial public demand for the state-of-the-art screening, in the United States especially. I here argue that, despite the prevailing official recommendations against any and all screening for lung cancer in the United States and Canada, it actually already is knowable that modern screening, with suitable specifications of both the screening itself and its recipient, not only is effective but can be effective enough to amply justify its cost. It thus is time for authorities to formulate, ever more inclusively, those cost-justifying specifications--and to promote research providing for further expansions of and innovations in them. American authorities, however, have not reacted this way to the new situation and, I dare say, they have been tenaciously irrational (and thereby irresponsible) in their underlying ideas about the nature of the proper knowledge-base for screening practice and of the research serving to advance this. It remains to be seen how timely, and how compellingly rational, the Canadian official reactions will be; and this too matters greatly, as countless lives hang in the balance, within Canada and, especially, in the world at large. Ex Canada lux?

Screening for lung cancer

Screening for lung cancer serves to prevent deaths from this disease insofar as earlier resections are associated with higher rates of cure. There is good reason to believe that this is the case: in stage I, the 5-year survival rate with resection is 70%, whereas without resection the corresponding rate is only 10%. Before this evidence emerged, various authoritative organizations and agencies in North America advised against screening for lung cancer on the grounds of the results of several RCTs. As for CXR, I argue that the study results are consistent with up to 40% reduction in the fatality rate. Moreover, modern helical CT screening provides for detecting much smaller tumors than were detected in those studies. It is time to revoke the conclusion that screening for lung cancer does not serve to prevent deaths from this disease, and to quantify the usefulness of CT screening in particular. As for the requisite research, the prevailing orthodoxy has it that RCTs are to be used, but I argue that more meaningful results are obtainable, more rapidly and much less expensively, by the use of noncomparative (and hence unrandomized) studies.

Etiologic research: needed revisions of concepts and principles

Even though etiologic research has been the central concern in academic epidemiology, its concepts have remained confused or malformed, starting from that of etiology itself; and the same applies to its principles, starting from the notion that the principal variants of an etiologic study are the 'cohort' study and the 'case-control' study. This article suggests revisions of some central concepts pertaining to the object (and objective) of an etiologic study, and it posits an updated conception of the essence--singular--the study itself. This is supplemented by some novel, yet merely orientational, propositions in respect to quality-assurance in etiologic research.

Early Lung Cancer Action Project: overall design and findings from baseline screening

BACKGROUND

The Early Lung Cancer Action Project (ELCAP) is designed to evaluate baseline and annual repeat screening by low-radiation-dose computed tomography (low-dose CT) in people at high risk of lung cancer. We report the baseline experience.

METHODS

ELCAP has enrolled 1000 symptom-free volunteers, aged 60 years or older, with at least 10 pack-years of cigarette smoking and no previous cancer, who were medically fit to undergo thoracic surgery. After a structured interview and informed consent, chest radiographs and low-dose CT were done for each participant. The diagnostic investigation of screen-detected non-calcified pulmonary nodules was guided by ELCAP recommendations, which included short-term high-resolution CT follow-up for the smallest non-calcified nodules.

FINDINGS

Non-calcified nodules were detected in 233 (23% [95% CI 21-26]) participants by low-dose CT at baseline, compared with 68 (7% [5-9]) by chest radiography. Malignant disease was detected in 27 (2.7% [1.8-3.8]) by CT and seven (0.7% [0.3-1.3]) by chest radiography, and stage I malignant disease in 23 (2.3% [1.5-3.3]) and four (0.4% [0.1-0.9]), respectively. Of the 27 CT-detected cancers, 26 were resectable. Biopsies were done on 28 of the 233 participants with non-calcified nodules; 27 had malignant non-calcified nodules and one had a benign nodule. Another three individuals underwent biopsy against the ELCAP recommendations; all had benign non-calcified nodules. No participant had thoracotomy for a benign nodule.

INTERPRETATION

Low-dose CT can greatly improve the likelihood of detection of small non-calcified nodules, and thus of lung cancer at an earlier and potentially more curable stage. Although false-positive CT results are common, they can be managed with little use of invasive diagnostic procedures.

Ideas and ideals in medicine: fruits of reason or props of power?

Editors of medical journals play a central role in the promotion -- or suppression -- of ideas and ideals in medicine. Recently eminent among these have been the advocacies of the Evidence-based Medicine (EBM) movement and others concerned with evidence and guidelines for health care. With regard to these topics, it still remains for editors of journals either to advance or to retard even the consolidation of the associated core concepts, most notably those of evidence in medicine, scientific medicine, and rational medicine. I present, first, a case study on the conduct of the editors of three medical journals, specifically their assumption of the role of authority on the scholarly fundamentals of evidence in medicine and their responding to propositions on the topic with commentaries well below the intellectual standards that should prevail in the journals of a learned profession. Then, following a brief review of the Flexnerian and EBM ideas and ideals on the practice of medicine, supplemented by observations drawn from medical sociology and the precepts of the philosophy of science, I posit a way of understanding such behaviour by editors of medical journals. They can have a temptation, and apparently some propensity, to play a regressive role in the development of the fundamentals of medicine. This is prone to occur whenever reason constitutes a threat to power, whether solely to the editors' own or to that of the profession at large. A full realization of the dream of reason in medicine requires an immense integrity of its journal editors and of its other intellectual leaders.

Evaluation of diagnostic imaging tests: diagnostic probability estimation

In the evaluation of a diagnostic imaging test for the diagnosis of a particular illness in a particular category of patients, the test should be construed as leading to a test result in the sense of a set of descriptive readings from the image(s), not interpretation of these; and in the evaluation of the test, therefore, the first challenge is the translation of each test result (set of readings) into the corresponding probability that the illness is present. This interpretive translation should not be subjective, nor should it be based on an objective algorithm founded on clinical judgments. Instead, a suitable diagnostic probability function (of the elements in the test result) should be derived empirically by logistic regression analysis of suitable data. We illustrate this alternative outlook by reanalysis of the data from the Prospective Investigation of Pulmonary Embolism Diagnosis.

Endometrial cancer risk after discontinuing use of unopposed conjugated estrogens (California, United States)

To examine the decline in risk of endometrial cancer after discontinuation of use of conjugated estrogens, we conducted a case-control study in a prepaid health plan. We identified 318 patients who had endometrial cancer but had no history of bilateral oophorectomy and had been in the Southern California (United States) Kaiser Foundation Health Plan for more than 10 years. For each patient, one or two control members were selected, 599 in all, matched for age and duration of membership at the time of cancer detection and who had had neither hysterectomy nor bilateral oophorectomy. A history of prescriptions for conjugated estrogens and of potential confounders was obtained for each subject by reviewing outpatient medical records. Rate ratios (RR) contrasting users with nonusers were estimated by time of latest prescription. We found that estrogen-induced risk of endometrial cancer decreases rapidly as the estrogen-free interval increases. The RR estimates, adjusted for duration of use and potential confounding factors, declined from 5.0 for those receiving their latest prescription within 24 months (95 percent confidence limits [CL] = 2.6-9.8), to 1.8 for those receiving their latest prescription within 24 to 48 months (CL = 0.9-3.7), to values near one for each latest prescription interval earlier than 48 months ago (P for trend = 0.00004). For those who used conjugated estrogens extensively (five or more prescriptions, five to 10 years ago), the RR estimate declined from 5.1 for those whose latest prescription was within two years to 0.6 yr for those whose latest prescription was four to five years previously (P for trend = 0.05).

Foundations of medical diagnosis: what actually are the parameters involved in Bayes' theorem?

Three decades ago, the thesis was adduced that setting diagnostic probabilities requires, by the inherent nature of diagnosis-pertinent medical knowledge, the use of Bayes' theorem. That paper was both vague and inconsistent in its delineation of the nature of the parameters involved in this formulation, and subsequent authors have only added to the confusion. Nevertheless, that thesis has been, and continues to be, enthusiastically embraced by clinical scholars. We here posit what those parameters must be taken to represent in principle; and this explication reveals that their quantification poses generally unsurmountable epistemologic challenges. The implication of this is not that informed setting of diagnostic probabilities is generally infeasible. Our conclusion is, instead, that the seminal thesis was founded on an untenable pair of premises about the nature of scientifically attainable knowledge pertinent to diagnosis.

Radiographic screening for cancer. Proposed paradigm for requisite research

Computed tomography (CT) imaging as an excellent approach to the detection and characterization of small solitary pulmonary nodules (SSPN) raises three questions: (1) How often does CT imaging lead to detection of SSPN? (2) How often is such an SSPN malignant? (3) If malignant, how curable is it? The first question pertains to decisions about screening use of CT (clinical or mass screening), the second to decisions about screening for SSPN and diagnosis of malignancy given SSPN, and the third--in the context of known curability at ordinary clinical diagnosis--to decisions about screening for SSPN, diagnosis given SSPN and intervention given malignant SSPN. We present a three component study design that addresses these questions. The first is directed primarily to the first question. Some 1000 persons at high risk for lung cancer will be screened for SSPN using screening-type CT. The primary aim is to determine the prevalence of CT-detectable SSPN as a joint function of risk-relevant aspects of the person. The second component addresses the prevalence of malignancy among the detected cases of SSPN. To develop the prevalence function, a larger series of CT-detected SSPN will be obtained by developing a multi-center SSPN "registry." A subsequent, third component will focus on the registered cases of malignant SSPN screening incidentally detected and address their curability on the basis of long-term follow-up. This design, in lieu of a randomized trial, may represent a new paradigm for applied research on radiologic technologies in cancer screening, given its advantages in terms of research efficiency and implications to decisions about diagnostic workup and therapeutic intervention.

Regional differences in breast cancer survival are correlated with differences in differentiation and rate of proliferation

Patients with invasive ductal breast cancer and with 5 to 12 years of follow-up, identified from two pathology laboratories serving hospitals in two distinct but fairly close regions, were studied for differences in length of survival. In the years when the cases were diagnosed, population screening was not performed, adjuvant systemic therapy was not administered, and surgical treatment and irradiation protocols were similar in the hospitals served by the two laboratories. There was a significant difference in length of survival between the two regional groups (N1 = 160, N2 = 111; P = .006). Survival rate at 10 years in the two regions was 48% and 69%. Distribution of age, tumor size, and lymph node status (as negative or positive as well as number of positive nodes) were similar, but quantitative and qualitative microscopic features differed. Patients from the region in which the prognosis was less favorable had the higher median values for the mitotic activity index (14 v 4; P less than .0001) and for nuclear area (59.2 v 38.2; P less than .0001). Nuclear and histologic grade distributions were also different between the regions. Logistic regression analysis confirmed that the regional survival differences are correlated with the microscopic features, even after adjustment for age, tumor size, and lymph node status. Comparison of breast cancers from the periods 1970 to 1974 and 1988 to 1989 in one of the two regions revealed that the clinical and microscopic proliferation features were similar over time. These results, apart from indicating regional variation in breast cancer survival rate correlated to differences in the microscopic characteristics of the disease between regions, provide additional support to previous reports that qualitative and, especially, quantitative microscopic differentiation and proliferation features have significant bearing on the prognosis of breast cancer patients.

Man-made mineral fibers and lung cancer. Epidemiologic evidence regarding the causal hypothesis

Reviews of the epidemiologic literature point to a causal connection between lung cancer and exposure to airborne man-made mineral fibers. The present critical re-review starts with the requirements for epidemiologic evidence to be informative regarding a hypothesis on cancer etiology. The previous reviews relate lung cancer mortality to exposure that is too recent to be relevant. The relation to relevant (distant) exposure in the available data involves notable confounding by coexposure to other agents in the work environment, by the lower socioeconomic status of the exposed workers, and possibly by smoking. Moreover, analyses of trends in standardized mortality ratios according to timing and duration of exposure involve a lack of mutual comparability between the ratios. Given these problems, the available evidence is inadequate for testing the causal hypothesis. However, reanalyses of the available data, augmentation of the data with reanalyses, and new studies could eliminate the existing inadequacies.

Health care research: what is it about?

Interest in research on health care has become quite substantial, in part as a result of the recent emergence of public-policy concern for quality assurance and cost-containment. Yet, the essence of this novel line of research has remained, regrettably, a matter of confusion. In particular, the distinction between health care research on one side and health research on the other is being missed in some eminent writings. We emphasize that, properly, the former is to be viewed as having health care, rather than health, as its object, and as being largely descriptive fact-finding about the nature and occurrence of various processes of health care. In these terms it serves policy and administrative decisions in the context of whatever knowledge is available from health research--as to the health consequences of such processes of care. Health research (applied), in turn, addresses the nature and occurrence of phenomena of health (their frequency)--in relation to type of health care, inter alia. Using the example of the North Karelia project, we illustrate the negative consequences of including under health care research inquiries into the premises of health care--notably studies on the effects of care on health outcome.

Medical research on a complaint: orientation and priorities

Low back pain as a research topic has been treated in this symposium, as in other contexts, as though it were an illness. It is, however, a complaint - and as such, even, potentially not a genuine one. Appreciation of the true character of back pain is essential for the proper orientation and setting of priorities for medical research as these flow from general principles of medical research in the domain of a complaint.

The clinical trial as a paradigm for epidemiologic research

The extent to which the clinical trial serves, and fails, as a paradigm for epidemiologic research in general is examined. It is argued, first, that the traditional paradigms--investigating epidemic and endemic occurrence of illness in the context of public-health activities, inclusive of the deployment of census, vital and morbidity statistics and sample surveys--are misleading for scientific research. Major examples of the consequences of these paradigms are the preoccupations with time and place, and with "the general population" or some other "target population"--both alien from the vantage of clinical trials and, indeed, of science in general. Then it is shown, by the use of the clinical trial paradigm, that traditional epidemiologic thought and practice in cause-effect research are misguided in the context of such common contexts as the use of empirical contrasts between exposure and unspecified nonexposure, the employment of "representative" distributions of determinants, and, even, as to the belief that cohort and "case-control" studies constitute alternatives to each other. On the other hand, it is argued that for etiologic research the ordinary (parallel) clinical trial is misleading as a paradigm, especially as for learning about the essential temporal aspects of the cause-effect relation.

Principles of nonexperimental assessment of excess risk, with special reference to adverse drug reactions

The risk of a particular kind of adverse reaction to a particular agent must be thought of with reference to the contemplated type of exposure and the type of person potentially exposed, and critically important in the contemplated exposure is its duration. In the general case, a distinction has to be made between risk during exposure and that after its discontinuation. For both of these risks, modifications of their magnitudes especially by previous exposure to the same agent must be considered. These risks are studied by focusing on incidence densities specific to subintervals of the total periods of risk. Assessment of these densities is generally best accomplished by following a (very large) dynamic (open) population, not specified on the basis of exposure. Cases of the adverse event, without regard for their etiology, that occur in this source population over the period of follow-up need to be identified and classified, first as to whether they arose from the study population proper or from the extraneous segment of the source population. Those arising from the study population and characterized by "recent" exposure--implying potential causation by it--need to be classified according to the attained duration of exposure and, where applicable, time since its discontinuation at the time of the inception of the adverse event. An appropriate sample of the source population over its follow-up needs to be obtained and classified in like manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Striving to deconfound the fundamentals of epidemiologic study design

The fundamentals of epidemiologic study design have remained a matter of confusion. Most authors still see the main design options to consist of the "cohort" study and the "case-control" study, augmented by the "cross-sectional" study. Others regard these as options only with respect to the perceived "directionality" dimension of design decisions. Few have come to appreciate that, realistically, there are no options as to directionality in the usual sense of "following forward" vs "investigating backward", or in the related sense of "inferential reasoning" being "from cause to effect" vs "from effect to cause". Related to this, few appreciate that the perceived duality of options constituted by "sampling by exposure" and "sampling by outcome" is, similarly, but an illusion. Old illusions like these confound the discernment of even those who, today, strive to deconfound the fundamentals of epidemiologic study design.

Quality of life from the epidemiologic perspective

In summary, from the epidemiologic perspective, the conference made it clear that: In modern occurrence research in medicine, quality of life is an important aspect of health outcome, along with duration of life; and it is of interest as a determinant of outcome as well. The concept of quality of life remains ill-defined but is, in the medical sense, some aggregate representation of disability discomfort, and distress resulting from illness and/or medical action. In medicine, quality of life is, in concept, specific to various types of clinical situation; and empirical scales need to be similarly situation-specific. Whereas clinical research on quality of life is already being conducted successfully, further development of scales specific to particular types of clinical situation remains a challenge to theorists of quality of life, as well as to experts on clinimetrics who collaborate with clinical specialists.

Power calculation in matched case-referent studies. Application and accuracy of the asymptotic power function

Although the asymptotic power function for matched case-referent (case-control) studies has been given, it is not widely applied. One reason for this is that the parameters in the power function do not correspond directly to the usual description of the research situation. When designing a matched case-referent study, the potentially available relevant information concerns the joint distribution of the determinant and matching variate, and the illness rate in relation to those factors, in the study base. Application of the asymptotic power function using these inputs is described. The asymptotic power function is then assessed by use of the Monte Carlo method and is found to be accurate. An example of the application of the asymptotic power function is given.

Perinatal risk assessment for patent ductus arteriosus in premature infants

Data from 2107 inborn premature infants monitored for hemodynamically significant patent ductus arteriosus were used to develop means for clinically assessing at birth the risk of developing patent ductus arteriosus during the first 30 days of life. The overall 30-day incidence rates in birth weight categories 500 to 999, 1000 to 1499 g, and 1500 to 1750 g were 41, 17, and 7%, respectively. At-birth risk estimates obtainable from the derived multivariate functions ranged from 0 to 78% for the 500 to 999 and 1000- to 1499-g categories, and from 0 to 20% for the 1500- to 1750-g category. The derived risk functions provide for enhanced selectivity in the application of measures for the prevention of patent ductus arteriosus.

Electrocardiogram of the premature infant at 1 year of age

ECGs were examined from 461 premature infants at 1 year of age. Data from those without a history of bronchopulmonary dysplasia were generally similar to published norms for healthy 1-year old infants. History and persistence of residual lung disease were reflected in the ECG by a high prevalence of findings suggestive of right ventricular hypertrophy. Clinically significant patent ductus arteriosus during the neonatal period did not influence the 1-year ECG findings. The data expand the published experience with follow-up ECGs from premature infants and suggest that the ECG may be a useful tool in follow-up of chronic residual lung disease in this population.

Side effects of non-narcotic analgesics as a determinant of prescribing

In the prescription of non-narcotic analgesics the physician's main responsibility is to make sure that the quality-of-life improvement expected from the drug's use justifies the associated risk, low though it is, of fatal side effects. The range of acceptable risk depends, naturally, on the dosage and duration of the treatment and on those characteristics of the patient which bear on the drug's efficacy and safety. In the treatment of acute pain an additional, very important, factor is the patient's remaining life expectancy. Quantification of maximal acceptable risks is aided by formal decision-analytic considerations. Such analyses indicate that maximal acceptable risks vary by several orders of magnitude among various clinical situations and that they are more liberal than intuition might generally suggest.

Risk factors for retrolental fibroplasia: experience with 3,025 premature infants. National Collaborative Study on Patent Ductus Arteriosus in Premature Infants

The rate of retrolental fibroplasia in relation to prenatal and neonatal characteristics was explored on the basis of a cohort of 3,025 neonates with birth weight less than 1,750 g. The overall rate of retrolental fibroplasia of any degree at hospital discharge was 11%, varying from 43% for those with birth weight between 500 and 749 g to 3% for those in the 1,500- to 1,750-g category. Among the potential determinants, the main interest was in nonhyperoxic characteristics, conditional on measures of prematurity and oxygen supplementation. Maternal diabetes and antihistamine use during the last 2 weeks of pregnancy were associated with significantly higher rates of retrolental fibroplasia, whereas toxemia was associated with lower rates. Frequent apneic spells, bronchopulmonary dysplasia, and sepsis in the neonate were also associated with significantly higher rates. On the other hand, the data indicate no independent role of low Apgar score, intraventricular hemorrhage, exchange transfusion, patent ductus arteriosus, or certain other characteristics previously postulated as risk factors.

Post-marketing studies of drug efficacy: why?

In order to quantify the need for post-marketing studies of drug efficacy, the 100 drug uses (i.e., drug-indication pairs) that were most common in 1978 were reviewed. Of the 100 most common drug uses, 31 were not Food and Drug Administration (FDA)-approved at the time of initial marketing and 18 had not become FDA-approved, even subsequently. In 13, the use was based on the drug's secondary effect rather than on the primary effects investigated before marketing. The efficacy of all was subject to modification by incompletely explored factors, including other drugs, patient age, other illnesses, pregnancy, etc. Specific examples are provided of important modifiers of the efficacy of these drugs that were not investigated prior to marketing. Thus, despite the existence of sufficient data for the regulatory process to permit the marketing of these commonly used drugs, considerable gaps remain in the information needed for their optimal clinical use. Post-marketing studies of drug efficacy will be needed to fill these gaps.