Comparison of sulfasalazine and placebo in the treatment of psoriatic arthritis. A Department of Veterans Affairs Cooperative Study

OBJECTIVE

To determine whether sulfasalazine (SSZ) at a dosage of 2,000 mg/day is effective for the treatment of active psoriatic arthritis (PsA) resistant to nonsteroidal antiinflammatory drug therapy.

METHODS

Two hundred twenty-one patients with PsA were recruited from 15 clinics, randomized (double-blind) to SSZ or placebo treatment, and followed up for 36 weeks. Treatment response was based on joint pain/ tenderness and swelling scores and physician and patient global assessments.

RESULTS

Longitudinal analysis revealed a trend favoring SSZ treatment (P = 0.13). At the end of treatment, response rates were 57.8% for SSZ compared with 44.6% for placebo (P = 0.05). The Westergren erythrocyte sedimentation rate declined more in the PsA patients taking SSZ than in those taking placebo (P < 0.0001). Adverse reactions were fewer than expected and were mainly due to nonspecific gastrointestinal complaints, including dyspepsia, nausea, vomiting, and diarrhea.

CONCLUSION

SSZ at a dosage of 2,000 mg/day is well tolerated and may be more effective than placebo in the treatment of patients with PsA.

Comparison of sulfasalazine and placebo in the treatment of reactive arthritis (Reiter's syndrome). A Department of Veterans Affairs Cooperative Study

OBJECTIVE

To determine whether sulfasalazine (SSZ) at a dosage of 2,000 mg/day is effective in the treatment of reactive arthritis (ReA) that has been unresponsive to nonsteroidal antiinflammatory drug (NSAID) therapy.

METHODS

One hundred thirty-four patients with ReA who had failed to respond to NSAIDs were recruited from 19 clinics, randomized (double-blind) to receive either SSZ or placebo, and followed up for 36 weeks. The definition of treatment response was based on joint pain/tenderness and swelling scores and physician and patient global assessments.

RESULTS

Longitudinal analysis revealed improvement in the patients taking SSZ compared with those taking placebo, which appeared at 4 weeks and continued through the trial (P = 0.02). At the end of treatment, response rates were 62.3% for SSZ treatment compared with 47.7% for placebo treatment. The Westergren erythrocyte sedimentation rate declined more with SSZ treatment than with placebo (P < 0.0001). Adverse reactions were fewer than expected and were mainly due to nonspecific gastrointestinal complaints.

CONCLUSION

SSZ at a dosage of 2,000 mg/day is well tolerated and effective in patients with chronically active ReA.

Implantable insulin pump vs multiple-dose insulin for non-insulin-dependent diabetes mellitus: a randomized clinical trial. Department of Veterans Affairs Implantable Insulin Pump Study Group

OBJECTIVE

To determine whether implantable insulin pump (IIP) therapy and multiple daily insulin (MDI) injections could equally attain improved blood glucose control, and to compare the 2 treatments with respect to reducing daily blood glucose fluctuations, reducing serious hypoglycemic insulin reactions, and improving patients' quality of life.

DESIGN

Randomized clinical trial.

SETTING

Seven Veterans Affairs medical centers.

PATIENTS

One hundred twenty-one male type II diabetic patients between the ages of 40 and 69 years, receiving at least 1 injection of insulin per day and having hemoglobin A1c (HbA1c) levels of 8% or above.

INTERVENTION

Intensive therapy (IIP or MDI) for 1 year.

MAIN OUTCOME MEASURES

Hemoglobin A1c and blood glucose levels.

RESULTS

Blood glucose levels declined to 7.96+/-1.08 mmol/L (143.4+/-19.5 mg/dL) and 8.30+/-1.52 mmol/L (149.6+/-27.4 mg/dL) (mean +/- SD) for IIP and MDI, respectively (P=.57). Hemoglobin A1c levels improved in both groups (time effect P<.001), to means of 7.54%+/-0.83% (MDI) vs 7.34%+/-0.79% (IIP). IIP reduced blood glucose fluctuations compared with MDI (P<.001), and reduced the incidence of mild clinical hypoglycemia by 68% (P<.001); IIP also eliminated the weight gain associated with MDI therapy and yielded better overall quality-of-life (P=.03) and impact-of-disease subscale scores (P=.05). Adverse events included 25% of subjects with episodes of insulin underdelivery due to microprecipitates of insulin within the pump.

CONCLUSIONS

Intensive insulin therapy with IIP and MDI is effective in controlling non-insulin-dependent diabetes mellitus. IIP has significant advantages in reducing glycemic variability, clinical hypoglycemia, and weight gain, while improving aspects of quality of life.

Does increased access to primary care reduce hospital readmissions? Veterans Affairs Cooperative Study Group on Primary Care and Hospital Readmission

BACKGROUND

For chronically ill patients, readmission to the hospital can be frequent and costly. We studied the effect of an intervention designed to increase access to primary care after discharge from the hospital, with the goals of reducing readmissions and emergency department visits and increasing patients' quality of life and satisfaction with care.

METHODS

In a multicenter randomized, controlled trial at nine Veterans Affairs Medical Centers, we randomly assigned 1396 veterans hospitalized with diabetes, chronic obstructive pulmonary disease, or congestive heart failure to receive either usual care or an intensive primary care intervention. The intervention involved close follow-up by a nurse and a primary care physician, beginning before discharge and continuing for the next six months.

RESULTS

The patients were severely ill. Half of those with congestive heart failure (504 patients) had disease in New York Heart Association class III or IV; 30 percent of those with diabetes (751 patients) had end-organ damage; and a quarter of those with chronic obstructive pulmonary disease (583 patients) required home oxygen treatment or oral corticosteroids. The patients had extremely poor quality-of-life scores. Although they received more intensive primary care than the controls, the patients in the intervention group had significantly higher rates of readmission (0.19 vs 0.14 per month, P = 0.005) and more days of rehospitalization (10.2 vs 8.8, P = 0.041). The patients in the intervention group were more satisfied with their care (P < 0.001), but there was no difference between the study groups in quality-of-life scores, which remained very low (P = 0.53).

CONCLUSIONS

For veterans discharged from Veterans Affairs hospitals, the primary care intervention we studied increased rather than decreased the rate of rehospitalization, although patients in the intervention group were more satisfied with their care.

Univariate analysis of dichotomous or ordinal data from twin pairs: a simulation study comparing structural equation modeling and logistic regression

The univariate analysis of categorical twin data can be performed using either structural equation modeling (SEM) or logistic regression. This paper presents a comparison between these two methods using a simulation study. Dichotomous and ordinal (three category) twin data are simulated under two different sample sizes (1,000 and 2,000 twin pairs) and according to different additive genetic and common environmental models of phenotypic variation. The two methods are found to be generally comparable in their ability to detect a "correct" model under the specifications of the simulation. Both methods lack power to detect the right model for dichotomous data when the additive genetic effect is low (between 10 and 20%) or medium (between 30 and 40%); the ordinal data simulations produce similar results except for the additive genetic model with medium or high heritability. Neither method could adequately detect a correct model that included a modest common environmental effect (20%) even when the additive genetic effect was large and the sample size included 2,000 twin pairs. The SEM method was found to have better power than logistic regression when there is a medium (30%) or high (50%) additive genetic effect and a modest common environmental effect. Conversely, logistic regression performed better than SEM in correctly detecting additive genetic effects with simulated ordinal data (for both 1,000 and 2,000 pairs) that did not contain modest common environmental effects; in this case the SEM method incorrectly detected a common environmental effect that was not present.

Statistical methods and strategies for working with large data bases

This article describes the statistical methods and strategies to be used in establishing the linkages between processes and structures of care with risk-adjusted outcomes in a large multicenter Veterans Affairs cooperative study in health services of patients undergoing cardiac surgery. The statistical analyses consist of test involving nine specific hypotheses related to the effect of processes and structures of care on risk-adjusted outcomes. From the statistical point of view, the major obstacles of this study are the need for data reduction and imputation of missing data. The former obstacle is addressed through the use of data-reduction techniques, such as principal components and cluster of variables. The latter is addressed through the use of classic and new techniques for imputation of missing data, such as MISSGEN, principal components for qualitative data, and the expectation and maximization algorithm. Data reduction and imputation of missing data are done with clinically derived variable groups called "dimensions" or "subdimensions." The effect of processes and structures of care is assessed by a two-step process. First, outcomes are modeled using only patient risk factors. The selection of risk factors in the modeling process is discussed in detail. Second, these risk-adjusted outcomes are modeled using one of the nine process or structure subhypotheses. The relationship of the processes and structures of care dimensions and/or subdimensions that are linked to risk-adjusted outcomes are identified.

An analysis of interobserver reliability and representativeness of data from the Veterans Affairs Cooperative Study on Processes, Structures, and Outcomes in Cardiac Surgery

The authors made some preliminary judgments regarding the reliability and representativeness of the data in the early stages of the Veterans Affairs Cooperative Study entitled Processes, Structures, and Outcomes of Care in Cardiac Surgery (PSOCS). Preliminary PSOCS interobserver reliability and potential patient and site selection bias reported were based on comparisons with identical risk, procedure, and outcome data items collected independently in the Continuous Improvement in Cardiac Surgery Study. PSOCS interobserver reliability for this limited set of variables was good to excellent. At the six pilot centers, there were few important differences between patients entered into PSOCS and those not entered. The 14 Veterans Affairs medical centers that will participate in the full-scale PSOCS study and the 29 nonparticipating centers exhibited similar patient populations. will be valuable.

Use of cumulative meta-analysis in the design, monitoring, and final analysis of a clinical trial: a case study

From 1983 to 1987, the Department of Veterans Affairs (DVA) Cooperative Studies Program (CSP) conducted a multicenter clinical trial (CSP #207) to determine whether four different antiplatelet regimens compared to placebo could prevent the occlusion of grafts following coronary artery bypass surgery. The study showed that all of the active regimens tended to be better than placebo and that the three regimens containing aspirin were statistically significantly better. A cumulative meta-analysis of 12 trials performed shortly before the end of CSP #207 raised the issue as to whether the meta-analysis, if done earlier, would have changed the conduct of the trial. At the start of the planning period, one trail of size n = 37 had been published with a nonsignificant odds ratio (OR) of 0.74 (95% CI: 0.18, 3.12). At the time that CSP # 207 was approved by the DVA Cooperative Studies Evaluation Committee, two trials had been published (cumulative n = 150, OR = 0.44, 95% CI 0.19, 0.99). At the time patient intake started, five trials showed cumulative n = 769, OR = 0.42, 95% CI = 0.26, 0.68. Although the first 6-month CSP #207 progress report showed no treatment effect, by the time of the 12-month review by the Data Monitoring Board (DMB) a trend was developing in favor of active treatment. If the results of the meta-analysis had been available to the DMB at that time, conceivably the Board would have recommended stopping the placebo arm because of a convincing treatment effect based on the totality of the evidence. Cumulative meta-analysis could be useful as an adjunct in the planning, conduct, and final analysis of a clinical trial. It could also be used as one piece of evidence in the monitoring of the ongoing phase of a trial.

The Processes, Structures, and Outcomes of Care in Cardiac Surgery study protocol

Recently, a growing interest has arisen in defining and measuring health care outcomes. Although outcome measures may be used as potential quality-of-care screens, outcomes cannot indicate directly how care might be improved. Thus, the Processes, Structures, and Outcomes of Care in Cardiac Surgery (PSOCS) study was designed to investigate the linkages between the processes and structures of care with risk-adjusted outcomes for cardiac surgery care. Data are being collected on a comprehensive array of risk factors, processes, structures, and outcomes of care at 14 Veterans Affairs Medical Centers for this prospective, observational study. Approximately 6,000 cardiac surgery patients will be enrolled in this study over a 4.5-year period. Patient selection is based on a 6 workday rotating sampling frame with an oversampling of emergent patients. During the study, a register of all patients undergoing cardiac surgery at these centers is being maintained to assess the overall context of patient recruitment. The study will continue to enroll patients through December 1996. Major study end points extend beyond traditional measures of 30-day mortality and morbidity to encompass more innovative intermediate outcome measures, including changes in physical functional status and health-related quality of life.

Variations in processes and structures of cardiac surgery practice

It is hypothesized that variations in the processes and structures of the selection of patients and the conduct of the surgical procedure may influence risk-adjusted outcome in patients undergoing cardiac surgery. For this reason, the results of the pilot phase of this Veterans Affairs cooperative study were reviewed to determine the variation in the operative practices at six pilot institutions. There were large variations in the percentage of elective, urgent, and emergent cases at each institution, ranging from 58% to 96% elective, 3% to 31% urgent, and 1% to 8% emergent. There was also a tenfold increase in the preoperative use of intra-aortic balloon pump for control of unstable angina, varying from 0.8% to 10.6%. Five of the six centers had accredited thoracic surgical residency programs. There was large variation in the preoperative participation of attending surgeons, from 100% participation at three centers to less than 5% in one. The operation was performed by the attending surgeon in 28% of cases, but this varied from 0% to 100%, depending on the hospital. Cold cardioplegia was used almost uniformly (99%) for myocardial protection; the use of retrograde cardioplegia varied from 2% to 89% among hospitals, and the use of blood cardioplegia ranged from 0% to 100%, with an average of 54% of cases. The use of myocardial temperature monitoring varied between hospitals, from 25% to 99%. The use of the cell saving devices to scavenge shed blood varied from 5% to 99%, and the frequency of the use of banked blood varied from 25% to 65%, depending on the institution. The internal mammary artery was used for 67% patients undergoing coronary artery bypass graft, with a variation between hospitals of 39% to 83%. One hospital used a single cross-clamping technique for the performance of proximal anastomoses in 95% of cases, as opposed to all other hospitals, who used this technique in less than 10% of cases. Aortic venting varied from 58% to 98% and left ventricular venting from 1% to 38%. The use of porcine valves varied approximately 15% in three hospitals to 30% to 40% in the other three hospitals. There were tremendous variations in the duration of operative procedure (5.2-7.3 hours), actual operating time (4.0-5.6 hours), total cardiopulmonary bypass duration (102-146 minutes), and ischemic time (50-87 minutes). The use of inotropic support varied from 41% to 91% between hospitals.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluating anesthesia health care delivery for cardiac surgery. The role of process and structure variables

Anesthesia care is an integral component of cardiac surgery. Emphasis on cost-effectiveness and decreased hospital stay has prompted reevaluation of anesthesia practice. However, the role of anesthesia process and structure variables in relation to patient outcomes is largely unknown. Processes, Structures and Outcomes of Care in Cardiac Surgery is the first epidemiologic study to collect data on anesthesia processes, such as the pharmacologic components of anesthesia and types of cardiovascular monitors used. Structures of care, such as resident staffing, supervision, completeness of documentation, and training and experience of care providers, are also being assessed. Pilot data collected from September 1992 to September 1993 demonstrate substantial variation between the six study sites in selected processes and structures. Despite the near-universal use of narcotic anesthesia as the primary anesthetic technique, variation in the type of opioid and adjuvant benzodiazepine used was observed. Regarding invasive hemodynamic monitoring, most centers used only one type of catheter. Intraoperative transesophageal echocardiography was used commonly at several centers for valve surgery, whereas other centers did not use it at all. Its use during coronary artery bypass grafting was less common. Assessment of the preoperative anesthesia note revealed that coronary anatomy and ventricular function were noted in nearly all instances. However, a clear notation that risks and benefits of anesthesia were discussed was less frequent. Structures related to anesthesia attending staffing, board certification, and experience revealed variation. Some sites had smaller and/or more experienced attending staffs, whereas others had larger and/or less experienced staffs. These pilot findings appear to validate the authors' hypotheses that variations in anesthesia practice are present within the Veterans Affairs system. They suggest that the variable set is robust enough to relate processes and structures of anesthesia care to patient outcome.

Results of combination anti-hypertensive therapy after failure of each of the components. Department of Veterans Affairs Cooperative Study Group on Anti-hypertensive Agents

We randomised ambulatory men with diastolic blood pressure (BP) 95-109 mmHg without anti-hypertensive medication to single drug treatment with either hydrochlorothiazide 12.5-50 mg/day, atenolol 25-100 mg/day, captopril 25-100 mg/day, clonidine 0.2-0.6 mg/day, diltiazem-SR 120-360 mg/day, prazosin 4-20 mg/day or placebo in a double-blind prospective trial. The assigned drug was titrated to a goal BP of < 90 mm Hg. Patients not achieving goal BP were rerandomised to an alternative single active drug. Non-responders to the second drug received the first drug in combination with the second. Of the 102 non-responders to both drugs who qualified for the combination, 59 (57.8%) responded. The combination pairs that included a diuretic achieved diastolic goal BP in 69% and < 140 mm Hg systolic in 77% compared with 51% and 46%, respectively, for those combinations without a diuretic (P = 0.067; P = 0.002). Six of the eight terminations due to adverse drug reactions were in combinations containing prazosin; three of these six were hypotensive reactions. We conclude that two single drugs of insufficient efficacy to control BP individually have a high probability of achieving goal BP when combined, especially if the combination contains a diuretic.

Development of an interactive data base management system for capturing large volumes of data

Accurate collection and successful management of data are problems common to all scientific studies. For studies in which large quantities of data are collected by means of questionnaires and/or forms, data base management becomes quite laborious and time consuming. Data base management comprises data collection, data entry, data editing, and data base maintenance. In this article, the authors describe the development of an interactive data base management (IDM) system for the collection of more than 1,400 variables from a targeted population of 6,000 patients undergoing heart surgery requiring cardiopulmonary bypass. The goals of the IDM system are to increase the accuracy and efficiency with which this large amount of data is collected and processed, to reduce research nurse work load through automation of certain administrative and clerical activities, and to improve the process for implementing a uniform study protocol, standardized forms, and definitions across sites.

Self-report measures for assessing treatment outcomes in cardiac surgery patients

Patient self-report measures are increasingly valued as outcome variables in health services research studies. In this article, the authors describe the Functional Status, Health Related Quality of Life, Life Satisfaction, and Patient Satisfaction scales included in the Processes, Structures, and Outcomes of Cardiac Surgery (PSOCS) cooperative study underway within the Department of Veterans Affairs health care system. In addition to reporting on the baseline psychometric characteristics of these instruments, the authors compared preoperative Medical Outcomes Study SF-36 data from the study patients with survey data from a probability sample of the US population and with preoperative data on cardiac surgery patients from a high volume private sector surgical practice. Descriptive analyses indicate that the SF-36 profiles for all of the cardiac patients are highly similar. The Veterans Affairs and private sector patients report diminished physical functioning, physical role functioning, and emotional role functioning as well as reduced energy relative to an age-matched comparison sample. At the same time, however, the Veterans Affairs patients evidenced lower levels of capacity on most of the SF-36 dimensions relative to the private sector patients.

A comparison of transurethral surgery with watchful waiting for moderate symptoms of benign prostatic hyperplasia. The Veterans Affairs Cooperative Study Group on Transurethral Resection of the Prostate

BACKGROUND

Transurethral resection of the prostate is the most common surgical treatment for benign prostatic hyperplasia. We conducted a multicenter randomized trial to compare this surgery with watchful waiting in men with moderate symptoms of benign prostatic hyperplasia.

METHODS

Of 800 men over the age of 54 years who were screened between July 1986 and July 1989, 556 (mean [+/- SD] age, 66 +/- 5 years) were studied (280 in the surgery group and 276 in the watchful-waiting group). Patients' symptoms and the degree to which they were bothered by urinary difficulties were measured with standardized questionnaires and medical evaluations. The primary outcome measure was treatment failure, which was defined as the occurrence of any of the following: death, repeated or intractable urinary retention, a residual urinary volume over 350 ml, the development of bladder calculus, new and persistent incontinence, a high symptom score, or a doubling of the serum creatinine concentration. Patients were followed for three years.

RESULTS

Of the men randomly assigned to the surgery group, 249 underwent surgery within two weeks after the assignment. Surgery was not associated with impotence or urinary incontinence. The average follow-up period was 2.8 years. In an intention-to-treat analysis, there were 23 treatment failures in the surgery group, as compared with 47 in the watchful-waiting group (relative risk, 0.48; 95 percent confidence interval, 0.30 to 0.77). Of the men assigned to the watchful-waiting group, 65 (24 percent) underwent surgery within three years after the assignment. Surgery was associated with improvement in symptoms and in scores for urinary difficulties and interference with activities of daily living (P < 0.001 for all comparisons). The outcomes of surgery were best for the men who were most bothered by urinary symptoms at base line.

CONCLUSIONS

For men with moderate symptoms of benign prostatic hyperplasia, surgery is more effective than watchful waiting in reducing the rate of treatment failure and improving genitourinary symptoms. Watchful waiting is usually a safe alternative for men who are less bothered by urinary difficulty or who wish to delay surgery.

A twin study of the association of post-traumatic stress disorder and combat exposure with long-term socioeconomic status in Vietnam veterans

This study examines the association between post-traumatic stress disorder (PTSD) and combat exposure with the socioeconomic status of 2210 male monozygotic veteran twin pairs in 1987. In the unadjusted analysis on individuals, modest correlations indicated that those with PTSD were more likely to have been divorced, and less likely to be currently employed or to achieve high status in income, education or occupation. In the crude analysis of veterans not suffering from PTSD, there were small positive correlations between combat level experienced and the likelihood of ever being married, ever being divorced, and the number of years employed at the current job. However, when we examined identical twins discordant for PTSD, and adjusted for pre-military and military service factors, only unemployment remained significant. Likewise, in combat-discordant twins, no significant effects on the socioeconomic indicators were seen. We conclude that PTSD and combat experience in Southeast Asia have not had a major impact on the socioeconomic status of veterans.

Importance of obesity, race and age to the cardiac structural and functional effects of hypertension. The Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents

OBJECTIVES

The purpose of this study was to determine the effects of obesity and its interaction with age, race and the magnitude of blood pressure elevation in a large cohort of patients with mild to moderate hypertension and a high prevalence of left ventricular hypertrophy.

BACKGROUND

Obesity, race and age each have important effects on the incidence and severity of hypertension and may contribute to the effects of blood pressure elevation on the cardiac manifestations of hypertension.

METHODS

Left ventricular structure and function were assessed with two-dimensional targeted M-mode echocardiography in 692 men with mild to moderate hypertension (average blood pressure 153/100 mm Hg), and the data were compared in relation to obesity (determined from body mass index), age, race, blood pressure, physical activity, plasma renin activity, urinary sodium excretion, hematocrit, heart rate and serum lipids.

RESULTS

Left ventricular hypertrophy was common (63% with increased left ventricular mass, 22% with left ventricular hypertrophy on the electrocardiogram [ECG]). On multivariable regression analysis, body mass index was the strongest predictor of left ventricular mass and magnified the slope relation of blood pressure to left ventricular mass. Despite a greater prevalence of ECG left ventricular hypertrophy in blacks (31%) than in whites (10%), left ventricular mass and echocardiographic prevalence of left ventricular hypertrophy did not differ by race. However, septal, posterior left ventricular and relative wall thickness were greater in black than in white men.

CONCLUSIONS

Obesity is the strongest clinical predictor of left ventricular mass and left ventricular hypertrophy in men, even in those with mild to moderate hypertension of sufficient severity to be associated with a high prevalence of left ventricular hypertrophy. Moreover, independent effects of systolic blood pressure on left ventricular mass are amplified by obesity. Although race does not affect left ventricular mass or the prevalence of left ventricular hypertrophy, black race is associated with greater relative wall thickness, itself a predictor of unfavorable cardiovascular outcome.

Meta-analysis of phenobarbital usage for prevention of intraventricular hemorrhage in premature infants: factors related to variation in outcome

PURPOSE

To assess the efficacy of phenobarbital for the prevention of intraventricular hemorrhage (IVH) in premature infants and to identify study characteristics that were associated with beneficial or adverse effects.

DATA IDENTIFICATION

Studies published from 1981 to 1994 were identified through a computerized search, and by searching the bibliographies of all identified articles.

STUDY SELECTION

Ten randomized, controlled clinical trials were selected.

DATA EXTRACTION

Data were extracted from each article, including the percentage of patients in the control and treatment groups with IVH, and key patient and study characteristics.

RESULTS OF DATA ANALYSIS

Seven studies showed no statistically significant effects, two studies showed a beneficial effect of phenobarbital, and one study showed an adverse effect. The meta-analysis showed no significant difference in the percentage of IVH in treated and untreated infants when treatment effects were combined across all studies. However, prenatal administration of phenobarbital in two studies was associated with a beneficial effect.

CONCLUSIONS

Overall, we did not find a significant beneficial effect of postnatal phenobarbital administration. The data suggests that prenatal phenobarbital is beneficial. Further evaluations of the efficacy of prenatal phenobarbital are warranted.

Assessment of predictive models for binary outcomes: an empirical approach using operative death from cardiac surgery

Predictive models in medical research have gained popularity among physicians as an important tool in medical decision making. Eight methodological strategies for creating predictive models are compared in a large, complex data base consisting of preoperative risk and operative outcome data on 12,712 patients undergoing coronary artery bypass grafting and entered into the Department of Veterans Affairs Cardiac Surgery Risk Assessment Program between April 1987 and March 1990. The models under consideration were developed to predict operative death (any death within 30 days following the surgical procedure or later if the result of a perioperative complication). The two strategies with the best predictive power among the eight examined were stepwise logistic regression alone and data reduction by cluster analysis combined with clinical judgement followed by a logistic regression model. The additive model based on unadjusted relative risks, the model based on Bayes' Theorem, and the logistic model using all candidate variables were good alternatives. Whether or not we imputed values did not have a significant impact on the predictive power of the models.

Determinants of the occurrence of and survival from prosthetic valve endocarditis. Experience of the Veterans Affairs Cooperative Study on Valvular Heart Disease

For the determination of the risk factors associated with the development of and death caused by prosthetic valve endocarditis, data were reviewed from 66 patients who were prospectively entered into the Veterans Affairs Cooperative Study on Valvular Heart Disease and in whom prosthetic valve endocarditis subsequently developed. Data were recorded at 13 medical centers between October 1977 and September 1982 in patients randomized to receive a mechanical valve (Bjork-Shiley spherical disc, n = 510 patients) or a bioprosthetic valve (Hancock porcine heterograft, n = 522 patients). The average rate of prosthetic valve endocarditis development was 0.8% per year over an average follow-up period of 7.7 years. Of the 66 patients in whom prosthetic valve endocarditis developed (5.8%), 15 cases occurred within 2 months of operation (early) and 51 occurred after operation (late). The most significant preoperative predictor of prosthetic valve endocarditis was active endocarditis at the time of operation (7.4% versus 0.9%) (p = 0.001). Early prosthetic valve endocarditis occurred more frequently in patients who underwent operation for multivalvular disease (p = 0.023). Significantly related perioperative variables were coma, prolonged mechanical ventilation, deep postoperative wound infection, postoperative jaundice, ventricular tachycardia, ventricular fibrillation, and replacement of more than one valve (p < 0.05). Multivariate predictors were hypoxia (p = 0.001), preoperative endocarditis (p = 0.003), preoperative valve lesion (p = 0.020), and resident surgeon (p = 0.05). Significant preoperative variables predictive of late prosthetic valve endocarditis were mitral stenosis and mixed mitral stenosis-regurgitation. The only multivariate predictor of late prosthetic valve endocarditis was superficial wound infection (p = 0.004). Of deaths attributable to prosthetic valve endocarditis, 41% occurred in patients treated with antibiotics alone, 48% occurred in patients treated with surgical intervention and antibiotics, and death resulted in both patients who received no treatment. No difference was found in the risk of early or late postoperative prosthetic valve endocarditis developing in patients receiving the mechanical valve versus those receiving the bioprosthetic valve.

Mutagenicity of ethanolic extracts of used acrylic dentures

The in vivo physicochemical sorption of mutagenic substances onto acrylic polymers was investigated in worn acrylic dentures. Thus, ethanolic extracts of acrylic dentures from 41 of a total of 69 human donors (60%), were found mutagenic in the standard plate incorporation Salmonella mutagenicity test against either TA98 or TA100 strains. Denture extracts from smokers produced mutagenicity more often than the ones from non-smokers (75% vs. 45%, P 0.01). Mutagenicity was preferentially directed against TA98 (TA98:TA100 = 2.9:1, P < 0.0005). Predilection for TA98 was more pronounced in denture extracts from non-smokers (4.7:1) than from smokers (2.0:1). When direct mutagenicity was observed, it was reduced by the rat-liver S9. Induced mutant yields were 6.1 +/- 3.9 and 7.0 +/- 8.9 times higher than the spontaneous for TA98 and TA100 respectively (smokers, 50-cm2 denture surface area eq./plate+S9). Denture extracts from smokers induced higher levels of mutation than the ones from non-smokers (TA98 + S9, smoker:non-smoker = 2:1, P < 0.01). Mutagenicity was associated with longer periods of denture usage (P 0.007). Thus, denture poly(methyl methacrylate) base material can adsorb mutagenic substances, possibly from diet and tobacco, which are extractable by ethanol. Theoretically, the in situ alcoholic desorption and recirculation of carcinogenic mutagens may have a contributory role in certain cases of intra-oral and upper alimentary tract carcinogenesis.

Comparison of the causes of late death following aortic and mitral valve replacement. VA Co-operative Study on Valvular Heart Disease

This report examines and compares the causes of late non-surgical death in 146 of 690 (21%) patients undergoing isolated aortic valve replacement (AVR) and in 79 of 273 (29%) patients undergoing mitral valve replacement (MVR) over a five year follow up period. The distribution of valve related, cardiac but not valve-related and non-cardiac deaths was 43%, 23% and 34% respectively for AVR and 65%, 29% and 6% respectively for MVR; the difference between these distributions was statistically significant. The specific causes of valve related deaths included bleeding (11% vs. 5% for MVR vs. AVR), systemic embolization (6% vs. 4% for MVR vs. AVR), endocarditis (14% vs. 8% for MVR vs. AVR), valve regurgitation (8% vs. 5% for MVR vs. AVR) and valve obstruction (3% vs. 5% for MVR vs. AVR). Sudden death (less than one hour from the onset of acute symptoms) accounted for 23% of deaths for MVR and 16% for AVR. The deaths due to congestive heart failure with normal prosthetic valve function were 13% and 8% for MVR and AVR respectively. Non-cardiac causes accounted for only 6% of MVR deaths but 34% of AVR deaths (p < 0.001). There was no significant difference in the late mortality between mechanical and bioprosthetic valves in the aortic position (24% vs. 22%), but the cumulative rate of late deaths was higher in patients with the Björk-Shiley than with the Hancock valve in the mitral position (41% vs. 25%, p < 0.02). In conclusion, about one quarter of patients surviving either aortic or mitral valve replacement died within five years.(ABSTRACT TRUNCATED AT 250 WORDS)

A strategy for assembling samples of adult twin pairs in the United States

In this paper we develop a methodology for the identification of large numbers of U.S. adult twin pairs. Data for this study derive from the U.S. Department of Defense and the Vietnam Era Twin (VET) Registry. The Department of Defense identified potential male twins (n = 10,002) using a computerized record linkage algorithm based on the same last name, same date of birth, and the same first five digits of the Social Security number. Twinship was confirmed by comparison with the Vietnam Era Twin Registry. We developed a logistic regression model that predicts the probability that a paired record identifies twins based on the absolute difference in the last four digits in the Social Security number, the age of issuance of the Social Security number, and the frequency of occurrence of the last name. We used the estimated coefficients derived from this regression model to assign predicted probabilities of being a twin to each matched record. There is a close correspondence between the observed and expected number of twins when evaluated across deciles of predicted probabilities of being a twin; the value of the Harrell's c index (c = 0.68 +/- 0.0004) indicates the overall predictive accuracy of the regression equation. The results from this study demonstrate the feasibility of identifying adult male-male twin pairs from any large computerized database that contains name, date of birth and Social Security number. However, the selection criteria used in the creation of the computer database must be clearly specified to avoid constructing a biased sample of twins.

Racial comparison of outcomes of male Department of Veterans Affairs patients with lung and colon cancer

BACKGROUND

A study was performed to distinguish between genetic vs socioeconomic factors or artifacts inherent in retrospective studies to discover explanations for the apparent shorter survival of blacks than whites with lung and colon cancer.

METHODS

Detailed biological and socioeconomic data were collected prospectively from a large cohort of patients with advanced lung and colon cancer who had not previously received chemotherapy and who consented to be entered in the clinical trial. Twelve medical centers within the Department of Veterans Affairs hospital system (Veterans Affairs Cooperative Study 188) entered patients between May 1981 and May 1986. These patients were evaluated and treated in a uniform manner within this hospital system and followed up to death. Outcome measures included time to tumor progression, tumor response, and survival.

RESULTS

A total of 719 patients were entered in the study, 704 of whom were either black or white men. Blacks were found to have a significantly lower socioeconomic status than whites as measured by marital and educational status, occupation, income, housing, and number of individuals residing in household. Blacks had a significantly lower frequency of prior tumor resection and a significantly increased frequency of mediastinal lymph node involvement and of metastasis than whites. Trends existed toward a shorter time interval from original diagnosis to entry and a lower frequency of prior radiation therapy among blacks in comparison with whites at the time of entry to the study. However, no differences in intensity of treatment or follow-up, time to progression, response to treatment, or overall survival (measured from entry to the study to death) were observed for blacks vs whites.

CONCLUSIONS

Lung and colon cancer are not necessarily more aggressive diseases in blacks than in whites. Based on a comparison of these data with those reported from other practice settings, we postulate that lung and colon cancer outcomes may be similar among black and white patients who receive equal access to comparable medical care in spite of socioeconomic differences. Findings suggest that future studies might focus profitably on racial factors that may exist at the time of patient entry to the health care system.

A comparison of outcomes in men 11 years after heart-valve replacement with a mechanical valve or bioprosthesis. Veterans Affairs Cooperative Study on Valvular Heart Disease

BACKGROUND

Mechanical heart valves are durable but thrombogenic, and their use requires that the patient receive anticoagulants. In contrast, bioprosthetic valves are less thrombogenic, but they have limited durability because of tissue deterioration.

METHODS

To compare the outcomes of patients who receive these two types of valves, we randomly assigned 575 men scheduled to undergo aortic-valve or mitral-valve replacement to receive either a mechanical or a bioprosthetic valve. The primary end points were death from any cause and any valve-related complication.

RESULTS

During an average follow-up of 11 years, there was no difference between the two groups in the probability of death from any cause (11-year probability for mechanical valves, 0.57; for bioprostheses, 0.62; P = 0.57) or in the probability of any valve-related complication (0.65 and 0.69, respectively; P = 0.39). There was a much higher rate of structural valve failure among patients who received bioprosthetic valves (11-year probability, 0.15 for the aortic valves and 0.36 for the mitral valves) than among those who received mechanical valves (no valve failures; P < 0.001). However, this difference was offset by a higher rate of bleeding complications among patients with mechanical valves than among those with bioprosthetic valves (11-year probability, 0.42 and 0.26, respectively; P < 0.001) and by a greater frequency of peri-prosthetic valvular regurgitation among patients with mechanical mitral valves than among those with mitral bioprostheses (11-year probability, 0.17 and 0.09, respectively; P = 0.05).

CONCLUSIONS

After 11 years, the rates of survival and freedom from all valve-related complications were similar for patients who received mechanical heart valves and those who received bioprosthetic heart valves. However, structural failure was observed only with the bioprosthetic valves, whereas bleeding complications were more frequent among patients who received mechanical valves.