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J Concato

Publications and source records attributed to J Concato.

47 records · Page 3Linked to original sources
PubMed1995

Importance of events per independent variable in proportional hazards analysis. I. Background, goals, and general strategy.

Multivariable methods of analysis can yield problematic results if methodological guidelines and mathematical assumptions are ignored. A problem arising from a too-small ratio of events per variable (EPV) can affect the accuracy and precision of regression coefficients and their tests of statistical significance. The problem occurs when a proportional hazards analysis contains too few "failure" events (e.g., deaths) in relation to the number of included independent variables. In the current research, the impact of EPV was assessed for results of proportional hazards analysis done with Monte Carlo simulations in an empirical data set of 673 subjects enrolled in a multicenter trial of coronary artery bypass surgery. The research is presented in two parts: Part I describes the data set and strategy used for the analyses, including the Monte Carlo simulation studies done to determine and compare the impact of various values of EPV in proportional hazards analytical results. Part II compares the output of regression models obtained from the simulations, and discusses the implication of the findings.

Computer Simulation↗
PubMed1995

Sex differences in the management of patients hospitalized with ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: Previous studies suggest that the management of coronary artery disease differs for women compared with men. We examined this issue for ischemic cerebrovascular disease. METHODS: We reviewed the use of angiography and carotid endarterectomy among patients discharged from Connecticut hospitals during 6 years over the past decade. Crude and age-adjusted rates of angiography and endarterectomy were determined for each sex. RESULTS: Among 22,582 female and 19,729 male patients discharged, the rate of cerebral angiography was 11.8% for men and 7.2% for women; the age-adjusted odds ratio was 0.77 (95% confidence interval [CI], 0.72 to 0.82). The rate of endarterectomy was 10.6% for men and 5.7% for women; the age-adjusted odds ratio was 0.67 (95% CI, 0.62 to 0.72). The distribution of cerebrovascular disease type differed by sex, however, with carotid artery disease representing a larger proportion of men (12.2% [2415/19,729]) than women (6.9% [1554/22,582]) (chi 2 = 355.8, P < .0001). When restricted to this diagnosis, no sex differences exist (odds ratio for angiography, 1.00 [95% CI, 0.87 to 1.14] and for endarterectomy, 0.93 [95% CI, 0.81 to 1.07]). CONCLUSIONS: Overall, women hospitalized for ischemic cerebrovascular disease undergo fewer angiograms and are less likely to have carotid endarterectomy than men. These differences are not found when analysis is restricted to subjects with carotid disease and suggest that part of the difference in management may be due to biological differences between men and women.

Aged↗
PubMed1994

Endemic tuberculosis among homeless men in New York City.

OBJECTIVES: The purpose of the study was to describe demographic and clinical characteristics of patients at the only long-term care facility for homeless men with tuberculosis in New York City, and to evaluate the outcome of a directly observed therapy program for these men. METHODS: The study population included residents at the "tuberculosis unit" for men in the New York City municipal shelter system. A cross-sectional survey described the characteristics of 76 men in the unit during November 1991. A retrospective cohort study evaluated 104 consecutive admissions to the facility from October 1, 1990, through March 30, 1991, and determined the outcome of directly observed therapy. RESULTS: Cross-sectional survey (n = 76). The median age was 43 years (range, 25 to 60 years); 67 patients (88%) had pulmonary tuberculosis. Among 58 isolates of Mycobacterium tuberculosis, eight were resistant to one drug (14%) and an additional nine were resistant to at least two drugs (16%). A history of previous treatment was associated with an odds ratio of 5.1 for having multiple drug-resistant tuberculosis (exact 95% confidence interval, 0.8 to 53.5). Retrospective cohort (n = 104). Excluding 21 men whose care was transferred to other agencies or institutions, 39 (47%) of 83 subjects completed or were still receiving treatment after 12 months and 44 (53%) of 83 subjects failed to complete the program. CONCLUSIONS: As expected, previous treatment for tuberculosis among homeless men is associated with an increased risk of having multiple-drug resistance. A directly observed therapy program successfully treated less than half of the enrolled subjects. Increased efforts are needed to control the spread of tuberculosis among homeless individuals.

Adult↗
PubMed1993

Granulocyte-colony stimulating factor therapy in drug-induced agranulocytosis.

Drug-induced agranulocytosis in the outpatient setting is a rare but potentially fatal adverse effect of many classes of medications. Five patients with this disorder presented to Yale-New Haven (Conn) Hospital during 1990 through 1992. Three patients treated with granulocyte-colony stimulating factor and two patients treated with routine care were studied for relevant clinical outcomes. Treatment with granulocyte-colony stimulating factor was associated with a shorter duration of neutropenia and a decreased length of hospital stay, consistent with recent case reports. Despite the high cost of the drug, treatment with granulocyte-colony stimulating factor was found to be cost-effective for patients with uncomplicated drug-induced agranulocytosis.

Adult↗
PubMed1993

The risk of determining risk with multivariable models.

PURPOSE: To review the principles of multivariable analysis and to examine the application of multivariable statistical methods in general medical literature. DATA SOURCES: A computer-assisted search of articles in The Lancet and The New England Journal of Medicine identified 451 publications containing multivariable methods from 1985 through 1989. A random sample of 60 articles that used the two most common methods--logistic regression or proportional hazards analysis--was selected for more intensive review. DATA EXTRACTION: During review of the 60 randomly selected articles, the focus was on generally accepted methodologic guidelines that can prevent problems affecting the accuracy and interpretation of multivariable analytic results. RESULTS: From 1985 to 1989, the relative frequency of multivariable statistical methods increased annually from about 10% to 18% among all articles in the two journals. In 44 (73%) of 60 articles using logistic or proportional hazards regression, risk estimates were quantified for individual variables ("risk factors"). Violations and omissions of methodologic guidelines in these 44 articles included overfitting of data; no test of conformity of variables to a linear gradient; no mention of pertinent checks for proportional hazards; no report of testing for interactions between independent variables; and unspecified coding or selection of independent variables. These problems would make the reported results potentially inaccurate, misleading, or difficult to interpret. CONCLUSIONS: The findings suggest a need for improvement in the reporting and perhaps conducting of multivariable analyses in medical research.

Humans↗
PubMed1992

Problems of comorbidity in mortality after prostatectomy.

OBJECTIVE: In recent studies of patients with benign prostatic hyperplasia (BPH), men undergoing transurethral resection of the prostate (TURP) had higher long-term mortality than men undergoing open prostatectomy. We tested the hypothesis that the higher mortality for patients undergoing TURP could have occurred if these patients were older and sicker at the time of surgery than patients undergoing open prostatectomy. DESIGN AND SETTING: Retrospective cohort study at Yale-New Haven (Conn) Hospital. PATIENTS: Two hundred fifty-two men who underwent TURP or open prostatectomy from 1979 through 1981 for the treatment of BPH. MAIN OUTCOME MEASURES: Five-year mortality adjusted for age and severity of comorbid illness at the time of surgery. RESULTS: The crude 5-year mortality rates were 17.5% (22 of 126 patients) for the TURP group and 13.5% (17 of 126 patients) for the open group. At the time of surgery, however, patients in the TURP group were sicker and older than patients in the open group. As the detail and quality of the assessment of comorbidity increased, the adjusted risk of TURP decreased. Improved classifications of comorbidity in three different forms of statistical analysis did not show an effect of type of prostatectomy on long-term mortality (Mantel-Haenszel relative risk, 1.03; 95% confidence interval, 0.57 to 1.87). CONCLUSIONS: These results suggest that TURP does not increase long-term mortality after surgery for the treatment of BPH. Inadequate accounting for severity of illness may also affect other statistical "adjustments" used in research concerned with patient outcomes.

Age Factors↗
PubMedDate not supplied

Comparison of dermatologic diagnoses by primary care practitioners and dermatologists. A review of the literature.

BACKGROUND: Cost-containment efforts in the United States have led to a greater emphasis on health care delivery by primary care physicians as opposed to specialists, who are assumed to be more costly. With this approach, it is incumbent on the primary care physician to be able to accurately diagnose and treat common maladies, including skin disease. OBJECTIVE: To ascertain whether differences in performance were detectable between groups of physicians when presented with color slides or high-quality transparencies. DESIGN: We performed a critical review of published studies. RESULTS: Overall, dermatologists (93% correct) performed better than nondermatologists (52% correct) (P < .001). No difference was appreciable between dermatology residents (91% correct) and practicing dermatologists (96% correct) or between internal medicine residents (45% correct) and family practice residents (48% correct). In addition, family medicine attending physicians (70% correct) performed better than internal medicine attending physicians (52% correct) (P < .001). CONCLUSION: Primary care physicians should receive more training in the diagnosis of skin disease.

Clinical Competence↗
PubMedDate not supplied

Informed consent for PSA screening: does it happen?

CONTEXT: Screening for prostate cancer with serum prostate-specific antigen (PSA) is controversial. Ideally, patients should be aware of the potential benefits and risks related to testing. PURPOSE: To assess whether patients remembered having PSA screening and to determine whether they recalled having a discussion with their primary care provider about the pros and cons of such testing. METHODS: A questionnaire was sent to patients who had PSA screening ordered by a primary care practitioner during a 2-month period at a university-affiliated Veterans Affairs medical center. Approximately 3 months after the PSA test was done, patients were asked about their baseline health as well as their knowledge of and attitudes toward screening with PSA and treatment for prostate cancer. RESULTS: The overall response rate was 197 out of 421 (46%) patients. Among 173 eligible respondents without prostate cancer, 53 (31%) were unaware that their physician had ordered a PSA test. Among the 120 patients who were aware of receiving the test, only 56 (47%) recalled having a discussion with their primary care provider about the risks and benefits of screening. Support for the test was more common among patients who recalled having PSA screening than those who did not recall having the test (91% vs. 70%, respectively; P = 0.003). CONCLUSIONS: Patients who have PSA screening often are unable to recall relevant facts about the test and may have no knowledge of its associated risks and benefits. The role and effectiveness of obtaining verbal informed consent for PSA screening should be re-evaluated.

Adult↗