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C H Schmid

Publications and source records attributed to C H Schmid.

70 records · Page 4Linked to original sources
PubMed1995

Cumulative meta-analysis of clinical trials builds evidence for exemplary medical care.

Cumulative meta-analysis of clinical trials (a Bayesian interpretation for accumulating evidence) will profoundly affect medical care by summarizing evidence in the assessment of technology innovations. Application of the technique to the randomized control trials (RCTs) of streptokinase treatment of acute myocardial infarction, reduction of peri-operative mortality by antibiotic prophylaxis, and prevention of death from bleeding peptic ulcers has revealed efficacy years before it was suspected by any other means. Arrangement of the trials according to event rate in the controls, effect sizes, quality of the trials or according to covariables of interest has supplied unique information. If carried out prospectively the technique supplies invaluable information regarding indications for another trial, the number of patients necessary to determine the validity of past trends, and the type of patients who might be benefitted. Careful examination in a cumulative manner of the prior trials can reduce the need for future large trials.

Bayes Theorem↗
PubMed1995

A model to assess severity and impact of fibromyalgia.

OBJECTIVE: To establish a model for the detection of specific factors associated with the severity of symptoms and the impact of fibromyalgia (FM). METHODS: We evaluated 332 consecutive new patients with FM for factors that may be associated with disease severity, assessed by patient global assessment, and function, evaluated by the Fibromyalgia Impact Questionnaire (FIQ). Fifteen potential explanatory factors were evaluated in a multiple linear regression model on data taken from an extensive group of standardized instruments. RESULTS: Of the 15 factors, pain levels, self-assessed inability to work, psychological distress, pending litigation, helplessness, level of education, and coping ability had a significant association with patients' global assessment and with scores on the total FIQ as well as on the activities of daily living subcomponent of the FIQ. CONCLUSION: Disease related factors such as pain and psychological factors such as work status, helplessness, education, and coping ability had an independent and significant relationship to FM symptom severity and function.

Adult↗
PubMed1994

Treatment of Lyme arthritis.

OBJECTIVE: To test treatment regimens for Lyme arthritis. METHODS: Patients were randomly assigned to treatment with doxycycline or amoxicillin plus probenecid for 30 days. Patients who had persistent arthritis for at least 3 months after treatment with oral antibiotics or parenteral penicillin were given intravenous ceftriaxone for 2 weeks. RESULTS: Eighteen of the 20 patients treated with doxycycline and 16 of the 18 patients who completed the amoxicillin regimen had resolution of the arthritis within 1-3 months after study entry. However, neuroborreliosis later developed in 5 patients, 4 of whom had received the amoxicillin regimen. Of 16 patients (2 from the oral antibiotic study and 14 additional patients) who had persistent arthritis despite previous oral antibiotics or parenteral penicillin, none had resolution of the arthritis within 3 months after ceftriaxone therapy. The HLA-DR4 specificity and OspA reactivity were associated with a lack of response. CONCLUSION: Lyme arthritis can usually be treated successfully with oral antibiotics, but patients may still develop neuroborreliosis. Patients with certain genetic and immune markers may have persistent arthritis despite treatment with oral or intravenous antibiotics.

Adolescent↗
PubMed1994

A decision aid for referring patients with systolic murmurs for echocardiography.

OBJECTIVE: To describe the practice pattern of a group of primary care providers in ordering echocardiography for healthy patients and to derive a decision aid to identify patients with systolic murmurs who have significant cardiac lesions. DESIGN: Retrospective case review of clinical variables, including the demographic, historical, and physical examination features obtained from chart review of the physician evaluation prior to referral for echocardiography and the echocardiographic results, with both univariate and multivariate regression analyses used to identify variables predictive of positive echocardiographic outcomes and to derive a regression model. SETTING: General internal medicine clinic in an urban major teaching hospital. PATIENTS/PARTICIPANTS: 169 patients between the ages of 18 and 55 years selected retrospectively from medical records. MEASUREMENTS AND MAIN RESULTS: Symptoms and auscultatory findings were not predictive of positive echocardiographic outcomes among the patients referred for the test. For the patients who had systolic murmurs, a logistic regression model had three significant predictors of positive echocardiographic results: additional year of age (odds ratio: 1.08, 95% CI: 1.02-1.13; p = 0.007); male gender (odds ratio: 5.87, 95% CI: 1.99-17.3; p = 0.002); and murmur grade > or = 3 (odds ratio: 4.99, 95% CI: 1.27-19.6; p = 0.02). The receiver-operating characteristic (ROC) curve area for this model was 0.741. If women aged 35 years and less with murmur grades < or = 2 had not been referred, 47% of the echocardiographies could have been avoided while retaining a sensitivity of 90%. CONCLUSIONS: The study suggested that healthy patients with systolic murmurs are least likely to have positive echocardiographic results when they are young and female and have murmur grades < or = 2. More careful screening of this group might make unnecessary almost half of the echocardiographies yielding negative results ordered for healthy patients with systolic murmurs.

Adolescent↗
PubMed1994

An assessment of the positive predictive value and cost-effectiveness of dipyridamole myocardial scintigraphy in patients undergoing vascular surgery.

PURPOSE: The approach to cardiac risk stratification of patients undergoing vascular surgery continues to be controversial. The success of algorithms that use clinical risk factors to determine cardiac risk have been inconsistent. Dipyridamole myocardial scintigraphy (DMS) has been accepted as a sensitive, noninvasive approach to risk stratification with excellent negative predictive value. Low positive predictive value (PPV) of abnormal DMS scans is a shortcoming that contributes to extensive preoperative cardiac evaluation and intervention with associated morbidity, mortality, and cost in most patients who undergo uncomplicated vascular procedures, regardless of DMS results. METHODS: Over 6 years, 237 patients underwent DMS before surgical management of infrarenal aortic aneurysm, aortoiliac, or infrainguinal occlusive disease. The value of multiple clinical factors and DMS were assessed retrospectively for the prediction of perioperative myocardial infarction (MI), heart-related death, or preoperative selection for myocardial revascularization. Only congestive heart failure and two or more reversible defects on DMS were statistically significant on logistic regression analysis. RESULTS: The PPV of DMS was 19% for all patients with reversible defects, 12% for patients with one reversible defect, and 36.7% for patients with two or more reversible defects. The rates of cardiac death and MI were 1.3% and 5.9%, respectively. Perioperative echocardiography revealed unchanged postinfarction ejection fraction in most patients who experienced MI. Cost-effectiveness of DMS screening was evaluated. CONCLUSIONS: The costs per MI and cardiac death averted suggest a decline in cost-effectiveness of screening with DMS over time, assuming improving cardioprotective strategies of patient care. Clinical risk factors were minimally useful in the prediction of perioperative MI, heart-related death, or need for myocardial revascularization. The PPV of DMS is low, and the majority of MIs may be clinically insignificant. The cost-effectiveness of cardiac screening with DMS may not be justifiable given current trends of health care reform.

Aged↗
PubMed1994

Screening and confirmatory testing of cadaver organ donors for hepatitis C virus infection: a U.S. National Collaborative Study.

Hepatitis C virus (HCV) can be transmitted by organ transplantation. Cadaver organ donors are screened for HCV infection by testing for antibodies to HCV (anti-HCV). The prevalence of HCV infection and performance of anti-HCV tests in detecting HCV infection in organ donors are unknown. Sera from 3078 cadaver organ donors were tested for anti-HCV by a first generation enzyme-linked immunosorbent assay (ELISA1). Sera from all 137 ELISA1 positive donors and a random sample of 92 ELISA1 negative donors were tested for anti-HCV by a second generation ELISA (ELISA2) and for HCV RNA by the polymerase chain reaction. Organ bank records were reviewed for risk factors associated with HCV infection. Follow-up was available on 70 recipients of organs from 42 ELISA2 positive donors. The prevalence of HCV RNA, extrapolated to all 3078 donors, was 2.4%. Liver disease, anti-HCV and HCV RNA were detected more frequently among recipients of organs from ELISA2 positive donors with HCV RNA than from ELISA2 positive donors without HCV RNA. Among donors, the sensitivity and negative predictive value of the ELISA2 for HCV RNA were 100%. However, despite a specificity of 98.1%, the positive predictive value was only 55.1%. Clinical and laboratory characteristics did not distinguish ELISA2 positive donors with and without HCV RNA. The presence of serum HCV RNA in organ donors predicts the risk of transmission of HCV infection. Discarding organs from ELISA2 positive donors would eliminate transmission, but organs from 1.88 percent of donors would be wasted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Presenting pulse pressure predicts thrombolytic therapy-related intracranial hemorrhage. Thrombolytic Predictive Instrument (TPI) Project results.

BACKGROUND: In selecting patients with acute myocardial infarction for thrombolytic therapy, it is important to identify patients who are at high risk for intracranial hemorrhage, for whom thrombolytic therapy is ill advised. We hypothesized that presenting pulse blood pressure, representing the "hammer" effect on cerebral vessels and the effects of age on arterial compliance, might predict thrombolysis-related intracranial hemorrhage better than systolic, diastolic, or mean arterial blood pressures. METHODS AND RESULTS: Of 3483 Thrombolytic Predictive Instrument (TPI) Project subjects receiving thrombolytic therapy for acute infarction, we identified and obtained detailed clinical data on the 19 with treatment-related intracranial hemorrhages confirmed by computed tomography and on 175 matched controls. Systolic, diastolic, mean arterial, and pulse blood pressures were each significantly related to the occurrence of intracranial hemorrhage, with pulse pressure most highly related. The mean pulse pressure in patients who developed intracranial hemorrhage was 63 mm Hg, 34% higher than the 47 mm Hg mean value for those not developing hemorrhage (P = .0001). Excess pulse pressure, defined as the extent to which a patient's pulse pressure exceeded 40 mm Hg for systolic blood pressures of at least 120 mm Hg, was even more strongly related: its mean value of 23 mm Hg for patients was 130% higher than its mean value of 10 mm Hg for controls (P < .0001). With logistic regression models to estimate the relative risks (odds ratios) for intracranial hemorrhage conferred by each form of blood pressure, the relative risk for hemorrhage was greatest for excess pulse pressure: for each 10-point pulse pressure excess, the relative risk for intracranial hemorrhage was increased by 1.85 (P = .0002; 95% confidence interval [CI], 1.34 to 2.55) by itself and 1.76 (P = .001; 95% CI, 1.26 to 2.46) when adjusted for age. In this sample, excess pulse pressure by itself predicted hemorrhage as well as systolic pressure and age together. When excess pulse pressure was combined with age to make a logistic regression model predicting intracranial hemorrhage, age contributed less to the prediction than when combined with the other blood pressure forms, even though this model predicted better than any other combination of age and pressure (receiver-operating characteristic curve area, 0.82 versus 0.77 with systolic pressure and age, 0.75 with mean arterial pressure, 0.71 with diastolic pressure, and 0.81 with both systolic and diastolic pressures). CONCLUSIONS: We found that excess pulse blood pressure predicted thrombolysis-related intracranial hemorrhage better than other forms of pretreatment blood pressure, perhaps better describing the pathophysiology of intracranial hemorrhage, including the effect of age. These findings will need confirmation in larger studies with comparable clinical detail.

Aged↗
PubMed1994

The efficacy of specimen radiography in evaluating the surgical margins of impalpable breast carcinoma.

OBJECTIVE: The purpose of this study was to determine if the presence or absence of tumor at the surgical margin in cases of impalpable breast carcinoma could be predicted accurately with specimen radiography. MATERIALS AND METHODS: We obtained single-view radiographs of 119 consecutive surgical biopsy specimens of impalpable invasive or in situ ductal carcinoma. Radiographic lesions were classified as a mass with moderately well defined margins, a mass with poorly defined margins, or microcalcifications without an associated mass. The radiographic appearance of the impalpable cancer, the margin as judged from the specimen radiograph, the tumor's histologic appearance, and the histologic appearance of the tumor margin were then correlated. RESULTS: Specimen radiographs showed tumor at the surgical margin in 63 cases; 62 of these were confirmed histologically (positive predictive value, 98%). Specimen radiographs showed tumor-free surgical margins in 56 cases; 18 of these were confirmed histologically (negative predictive value, 32%). These results were independent of the radiographic appearance of the lesion or the tumor's histologic appearance. CONCLUSION: Decisions based on findings on specimen radiographs were valid only if the radiographs showed tumor at the margin of the specimen.

Biopsy↗
PubMed1994

Safety, accuracy, and diagnostic yield of needle localization biopsy of the breast performed using local anesthesia.

BACKGROUND: In changing our technique to performing needle localization breast biopsies (NLBB) using local anesthesia in an outpatient setting, we investigated whether or not our complication rates with local anesthesia were acceptable when compared with complications from a cohort of biopsies of the breast performed for palpable masses. We were also interested in determining whether or not our rate of missed biopsies was within acceptable ranges. STUDY DESIGN: Complications occurring in 283 patients who underwent 301 NLBB using local anesthesia between 1983 and 1991 were compared with complications occurring after excision of 249 palpable masses of the breast excised using local anesthesia during this period. RESULTS: Complications associated with NLBB were missed lesions, six (1.99 percent) of 301; hematoma, 12 (3.99 percent) of 301; abscess, three (0.99 percent) of 301; seroma, one (0.33 percent) of 301, and wound separation, two (0.66 percent) of 301, for a total of 24 complications (7.96 percent). These rates were not statistically different from the rates of complication after biopsies of palpable lesions using local anesthesia (p < 0.49). The 301 NLBB revealed 87 carcinomas (28.9 percent); 50 invasive and 37 in situ. Of the nonpalpable carcinomas, 43 percent were in situ. Only 11 percent carcinomas, 43 percent were in situ. Only 11 percent of the palpable lesions were in situ (p < 0.001). Forty-four patients with nonpalpable invasive carcinoma had a 25 percent rate of positive axillary lymph nodes. CONCLUSIONS: Needle localization breast biopsies can be performed using local anesthesia exclusively with less than a 2 percent chance of missed lesions and complication rates similar to those associated with biopsies of palpable lesions. The biology of these lesions varies. Although there is a high rate of in situ carcinoma, there is a significant rate of node positivity in the patients with nonpalpable invasive carcinoma.

Adolescent↗
PubMed1993

A Bayesian approach to logistic regression models having measurement error following a mixture distribution.

To estimate the parameters in a logistic regression model when the predictors are subject to random or systematic measurement error, we take a Bayesian approach and average the true logistic probability over the conditional posterior distribution of the true value of the predictor given its observed value. We allow this posterior distribution to consist of a mixture when the measurement error distribution changes form with observed exposure. We apply the method to study the risk of alcohol consumption on breast cancer using the Nurses Health Study data. We estimate measurement error from a small subsample where we compare true with reported consumption. Some of the self-reported non-drinkers truly do not drink. The resulting risk estimates differ sharply from those computed by standard logistic regression that ignores measurement error.

Age Factors↗
PubMed1993

A new noninvasive method for the estimation of peak dP/dt.

BACKGROUND: Peak dP/dt is a good index of ventricular performance that is not influenced by afterload, wall motion abnormalities, or the variations in ventricular anatomy and morphology commonly encountered among patients with congenital heart disease. Unfortunately, the clinical utility of peak dP/dt has been limited by the fact that its measurement generally requires an intraventricular catheter. However, peak dP/dt occurs during isovolumetric contraction, and the pressure rise during isovolumetric contraction is almost linear. Therefore, the mean dP/dt during isovolumetric contraction (mean dP/dtic), ie, the ratio of the rise in pressure during isovolumetric contraction (aortic diastolic pressure minus the systemic ventricular end-diastolic pressure [VEDP]) over the isovolumetric contraction time, should provide a good estimate of peak dP/dt that could be generated noninvasively. METHODS AND RESULTS: Echo/phonocardiography was used to measure the isovolumetric contraction time and a blood pressure cuff to estimate aortic diastolic pressure of 27 patients (age, 1 day to 77 years) with congenital or acquired heart disease. VEDP was determined by three methods: (1) intraventricular catheter, (2) assumed VEDP of 10 mm Hg, and (3) assignment of a normal or elevated value on the basis of clinical history. The three estimates of mean dP/dtic thus generated were compared with simultaneous measurements of peak dP/dt obtained during cardiac catheterization. Invasively measured peak dP/dt correlated well with the indirect determinations (r = .95, .89, and .92 for methods 1, 2, and 3, respectively; P < .0001). CONCLUSIONS: Echo/phonocardiography can be used in conjunction with a blood pressure cuff and indirect estimates of VEDP to generate mean dP/dtic, an index of ventricular function that approximates and closely correlates with peak dP/dt. This noninvasive measurement can be obtained in almost any patient and may be useful in the assessment of ventricular performance in a variety of cardiovascular disorders.

Adolescent↗
PubMedDate not supplied

Lansoprazole compared with histamine2-receptor antagonists in healing gastric ulcers: a meta-analysis.

To compare the gastric ulcer healing rates of lansoprazole with histamine2-receptor antagonists (H2RAs) (ranitidine, famotidine, cimetidine, and roxatidine), a meta-analysis was performed using data from five published and eight unpublished randomized controlled trials. Analyses were performed using (1) both evaluable patients (n = 1527) and all randomized patients (n = 1655) (assuming that patients lost to follow-up were treatment failures); (2) all studies and a subset of studies that received high methodologic quality scores; and (3) fixed-effects, random-effects, and Bayesian statistical models. In all cases, lansoprazole was associated with a significantly higher rate of endoscopic healing at both 4 and 8 weeks compared with the H2RAs. When the most conservative Bayesian statistical model and intent-to-treat analysis were used, lansoprazole was associated with a 33% higher healing rate at 4 weeks (risk ratio = 1.33; 95% confidence interval [CI] = 1.19 to 1.49) and a 12% higher healing rate at 8 weeks (risk ratio = 1.12; 95% CI = 1.06 to 1.19) than were the H2RA agents. Similar results were obtained when the meta-analysis was performed on evaluable rather than all randomized patients and using the three different analytical techniques noted above. Slightly lower, though still highly significant, improvement in ulcer healing rates was obtained when the meta-analysis was performed using a subset of six studies that received high methodologic quality scores. These results support the conclusion that lansoprazole heals ulcers more quickly than do the H2RAs and also achieves higher overall rates of healing. The eradication of Helicobacter pylori associated with gastric ulcers was not assessed in individual studies.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMedDate not supplied

Comorbidity assessment in hemodialysis and peritoneal dialysis using the index of coexistent disease.

The purpose of this paper is to describe the ICED, summarize outcomes of prior studies in which it was used, and describe the adaptations that have lead to the present instrument. We will then demonstrate its use in quantifying the burden of comorbid conditions in a sample of hemodialysis and peritoneal dialysis patients from our center, and show the relationship between ICED levels and outcomes in peritoneal dialysis patients.

Comorbidity↗
PubMedDate not supplied

The exclusion of women from clinical trials of thrombolytic therapy: implications for developing the thrombolytic predictive instrument database.

The thrombolytic predictive instrument (TPI) was developed to identify those patients most likely to benefit from thrombolytic therapy for acute myocardial infarction as well as to facilitate the earliest possible administration of this treatment. The TPI consists of predictive models derived from clinical data obtained from both clinical trials and data registries. These models are subject to potential bias due to combinations of primary data from different sources. The purpose of this investigation was to assess the influence of gender in developing the TPI database. In this database, there were 1,096 (22%) women and 3,826 (78%) men; only 38% of the women were enrolled in clinical trials, whereas 46% of the men were (p < 0.0001). Within clinical trials, there were few significant eligibility differences between women and men, as the vast majority of patients met eligibility standards for entry in these trials. However, within clinical registries, the women were older (p < 0.0001) and more often had elevated blood pressure on admission (p = 0.002). Multivariate logistic regression indicated that after adjustment for significant predictors of trial inclusion, women were 25% less likely to be included in clinical trials (odds ratio = 0.76, 95% confidence interval = 0.60, 0.96). In order to counter bias introduced by the exclusion of women from clinical trials, the TPI database included patients from non-trial settings. Carefully including patients from clinical registries or non-trial settings may be an important strategy in constructing generally applicable predictive instruments.

Aged↗
PubMedDate not supplied

Large trials vs meta-analysis of smaller trials: how do their results compare?

OBJECTIVE: To evaluate the results of large clinical trials vs the pooled results of smaller trials. DATA IDENTIFICATION: Meta-analyses with at least 1 "large" study were identified from the Cochrane Pregnancy and Childbirth Database and from MEDLINE (1966-1995). STUDY SELECTION: We used a sample size approach to select 79 meta-analyses with at least 1 large study of 1000 or more patients. We used a statistical power approach to select 61 meta-analyses with at least 1 large study based on statistical power considerations. DATA EXTRACTION: The outcome of interest for each meta-analysis was the primary one stated in the original publication or, when not clearly specified, was decided on clinically. DATA SYNTHESIS: By random effects calculations, we found agreement between large and smaller trials in 90% of the meta-analyses selected by the sample size approach and in 82% of the meta-analyses selected by the statistical power approach. Twice as many disagreements appeared when the variability among large studies and among smaller studies was not considered (ie, fixed effects calculations). Of the 15 disagreements between results of large and smaller trials using the random effects model, plausible explanations were identified in 10 meta-analyses: 5 with differences in the control rate of events between large and smaller trials, 4 with specific protocol or study differences, and 1 with potential publication bias. Two other disagreements were not clinically important, and tentative reasons could be identified for 2 of the remaining 3 disagreements. CONCLUSIONS: Results of smaller studies are usually compatible with the results of large studies, but discrepancies do occur even when the diversity among both large studies and smaller studies is considered. Clinically important differences without a potential explanation are extremely uncommon. Future research should further examine sources of heterogeneity between the results of large and smaller trials.

Bias↗