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PubMed2001

ROC optimization may improve risk stratification of prostate cancer patients.

OBJECTIVES: Rational treatment decision requires accurate projection of the clinical course of a patient. Current methods in clinical outcome analysis mostly focus on population data. We investigated the applicability and optimization of the widely used actuarial method to project individual clinical outcomes. METHODS: We designed and implemented a Clinical Outcome Prediction Expert (COPE) that performs, assesses, and optimizes actuarial prediction on individual cases. We analyzed a post-prostatectomy database, consisting of 1043 patients. Sixty percent of the database was used for training and 40% for validation. Stratified actuarial curves are used to project individual outcomes. The prostate-specific antigen (PSA) level, the Gleason score, and the clinical American Joint Commission on Cancer Staging T-stage before treatment were used as predictors. The area under the receiver operator characteristic (ROC) curve was used to measure predictive performance. RESULTS: We obtained simple optimized stratification of pretreatment PSA level of 10 ng/mL or less, or more than 10 ng/mL; Gleason score of 6 or lower, or higher than 6; and clinical AJCC T-stage of T2a or lower, or higher. The optimized univariate risk scores were used to generate a multivariate score. After optimization, we found the higher risk group consisted of patients with PSA more than 10 ng/mL, or with PSA of 10 ng/mL or less and Gleason score higher than 6 and clinical AJCC T-stage higher than T2a. The optimized multivariate risk score has the highest ROC area of 0.77 among all predictors. CONCLUSIONS: The best conditions to perform actuarial prediction on individual cases are not known a priori and require optimization. This study shows that ROC optimization simplifies risk stratification and may improve the accuracy of clinical outcome prediction.

Data Interpretation, Statistical↗

PubMed1994

Prospective risk stratification in renal transplant candidates for cardiac death.

In previous studies to predict future cardiac death of patients undergoing evaluation for renal transplantation, noninvasive or invasive testing of all, or nearly all, patients has been used. In an attempt to decrease the cost of cardiac risk assessment, we prospectively used a two-tiered cardiac risk assessment algorithm on 189 consecutive patients referred for renal transplant evaluation. First, patients were stratified by clinical characteristics of age > or = 50 years, history of angina, insulin-dependent diabetes, congestive heart failure, or abnormal electrocardiogram (excluding left ventricular hypertrophy). Patients having none of these risk factors (n = 94) were considered at low risk for cardiac events and underwent no further cardiac evaluation. Patients with one or more of the cardiac risk factors (n = 95) were considered to be in a high-risk group and were required to undergo further evaluation with thallium myocardial scintigraphy. Follow-up of patients was for 46 +/- 16 months. Cardiac mortality was significantly higher in the clinical high-risk group compared with the clinical low-risk group (17% v 1%, respectively; P < 0.001). Further cardiac risk stratification was evident by thallium myocardial scintigraphy. Patients with reversible thallium defects had significantly higher cardiac mortality rates than patients with no thallium defects (23% v 5%, respectively; P < 0.05). Fixed thallium defects also had predictive value for cardiac mortality (29%,; P < 0.05), but deaths in this fixed defect group tended to occur later in the follow-up period. The initial clinical stratification obviated the need for further noninvasive or invasive testing in nearly half of the renal transplant candidates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2000

Risk stratification in unstable coronary artery disease--exercise test and troponin T from a gender perspective. FRISC-Study Group. Fragmin during InStability in Coronary artery disease.

OBJECTIVES: The study was done to determine the prognostic yield of an early symptom-limited exercise test (ET) and measurement of troponin T (TnT) in men and women with unstable coronary artery disease (CAD), with special reference to gender differences. BACKGROUND: Early risk assessment is essential for the application of appropriate treatment and further management in patients with unstable CAD. The early symptom-limited ET together with specific biochemical marker determination is an inexpensive, widely applicable method for early risk stratification. In women, however, the ET is considered less reliable, and there are few data on biochemical markers for risk stratification in women. METHODS: In a substudy of the Fragmin during InStability in Coronary artery disease (FRISC I) trial, 395 women and 778 men with unstable CAD who performed an early ET were followed for six months. Blood samples for TnT determination were taken in 342 women and 621 men at inclusion. RESULTS: Based on the ET results, low-, intermediate-, and high-risk response groups were identified with event rates of cardiac death or myocardial infarction (MI) of 1%, 9%, and 19%, respectively, among women and 8%, 14%, and 20%, respectively, among men. Patients who could not perform the ET had an event rate similar to the high-risk group. The TnT levels were divided into three groups: <0.06, 0.06-0.19, and > or = 0.20 microg/liter with event rates of 1%, 10%, and 18%, respectively, among women and 9%, 14%, and 18%, respectively, among men. Combining the ET results with TnT levels identified a low-risk group with an event rate of 3% in the male population and no events in the female population. CONCLUSIONS: Direct comparison between men and women from the same population with a high pretest likelihood of disease suggests that both TnT and the early symptom-limited ET are at least as useful as prognostic risk indicators in women as they are in men.

Aged↗

PubMed2000

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification.

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.

Aged↗

PubMed2001

Prognostic stratification of diabetic patients by exercise echocardiography.

OBJECTIVES: The aim of this study was to assess the incremental value of exercise echocardiography for the risk stratification of diabetic patients. BACKGROUND: There are currently insufficient outcome data in diabetic patients to define the role of stress echocardiography as a prognostic tool. METHODS: We studied the prognostic value of exercise echocardiography in 563 patients with diabetes mellitus (mean age 64 +/- 11 years, 336 men) and known or suspected ischemic heart disease (IHD). RESULTS: Cardiac events occurred in 50 patients (cardiac death in 23 and nonfatal myocardial infarction [MI] in 27) during a median follow-up period of three years. Event rate was lower in patients with normal as compared to those with abnormal exercise echocardiography at one year (0% vs. 1.9%), three years (1.8% vs. 11.9%), and five years (7.6% vs. 23.3%), respectively (p = 0.0001). Patients with multivessel distribution of echocardiographic abnormalities had the highest event rate (2.9% at one year, 15.2% at three years, and 32.8% at five years). In an incremental multivariate analysis model, exercise echocardiography increased the chi-square of the clinical and exercise ECG model from 29 to 44.8 (p = 0.0001). CONCLUSIONS: Exercise echocardiography provides incremental data for risk stratification of diabetic patients with known or suspected IHD. Patients with a normal exercise echocardiogram have a low event rate. Patients with multivessel distribution of exercise echocardiographic abnormalities are at the highest risk of cardiac events, as one-third of these patients experience cardiac death or nonfatal MI during the five years following exercise echocardiography.

Aged↗

PubMed2001

Clinical risk stratification correlates with the angiographic extent of coronary artery disease in unstable angina.

OBJECTIVES: We sought to determine whether clinical risk stratification correlates with the angiographic extent of coronary artery disease (CAD) in patient with unstable angina. BACKGROUND: The Agency for Health Care Policy and Research (AHCPR) guidelines stratify patients with unstable angina according to short-term risk of myocardial infarction or death. Whether these guidelines are useful in predicting the extent of CAD is unknown. METHODS: All residents of Olmsted County, Minnesota, undergoing emergency department evaluation from January 1, 1985 through December 31, 1992 for unstable angina without a history of prior coronary artery bypass grafting, and who underwent early angiography (within seven days of presentation) were classified into low, intermediate and high risk subgroups based on AHCPR criteria. RESULTS: Seven hundred ninety-five patients underwent early angiography: 159 high risk, 572 intermediate risk and 64 low risk patients. Logistic regression analysis demonstrated that low risk patients had a greater likelihood of normal or mild CAD relative to intermediate risk (odds ratio [OR], 4.67; 95% confidence interval [CI], 2.70-8.06; p < 0.001) and high risk (OR, 11.1; 95% CI, 5.71-22.2; p < 0.001). Significant 1-, 2-, 3-vessel coronary disease or left main coronary disease was more likely in high relative to low risk (OR, 8.09; 95% CI, 4.22-15.5; p < 0.001), intermediate relative to low risk (OR, 4.11; 95% CI, 2.34-7.22; p < 0.001), and high relative to intermediate risk (OR, 1.97; 95% CI, 1.31-2.96; p = 0.0012). CONCLUSIONS: Among patients with unstable angina undergoing early coronary angiography, risk stratification according to the AHCPR guidelines correlates with the angiographic extent of CAD.

Adult↗

PubMed2001

Aortic stenosis with severe left ventricular dysfunction and low transvalvular pressure gradients: risk stratification by low-dose dobutamine echocardiography.

OBJECTIVES: We sought to assess risk stratification by using dobutamine stress echocardiography (DSE) in patients with aortic stenosis (AS) and severe left ventricular (LV) dysfunction. BACKGROUND: Few data are available on risk stratification for valve replacement in patients with AS, LV dysfunction and low transvalvular gradients. METHODS: Low-dose DSE was performed in 45 patients (16 women and 29 men; median [quartile range] age in years: 75 [69 to 79]; left ventricular ejection fraction: 0.29 [0.23 to 0.32]; aortic valve area [cm2]: 0.7 [0.5 to 0.8]; mean transaortic gradient [mm Hg]: 26 [21 to 33]). Patients were classified into two groups: group I (n = 32, LV contractile reserve on DSE) and group II (n = 13, no contractile reserve). Valve replacement was performed in 24 and 6 patients in groups I and II, respectively. RESULTS: Perioperative mortality was 8% in group I and 50% in group II (p = 0.014). Survival at five years after the operation was 88% in group I. Compared with medical therapy, valve surgery was associated with better long-term survival in group I (hazard ratio for death [HR-D] 0.13, 95% confidence interval [CI] 0.002 to 0.49) and reduced survival in group II (HR-D 19.6, 95% CI 2.7 to 142). The effect of valve surgery on survival remained significant in both groups after adjustment for age, diabetes, respiratory disease and hypertension. Medical therapy had the same effect in both groups. CONCLUSIONS: In patients with AS, LV dysfunction and low transvalvular gradients, contractile reserve on DSE is associated with a low operative risk and good long-term prognosis after valve surgery. In contrast, operative mortality remains high in the absence of contractile reserve.

Aged↗

PubMed2001

Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population.

OBJECTIVES: This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population. BACKGROUND: In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses. METHODS: We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996. RESULTS: During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively. CONCLUSIONS: Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.

Aged↗

PubMed2001

Utility of current risk stratification tests for predicting major arrhythmic events after myocardial infarction.

OBJECTIVES: We surveyed the literature to estimate prediction values for five common tests for risk of major arrhythmic events (MAEs) after myocardial infarction. We then determined feasibility of a staged risk stratification using combinations of noninvasive tests, reserving an electrophysiologic study (EPS) as the final test. BACKGROUND: Improved approaches are needed for identifying those patients at highest risk for subsequent MAE and candidates for implantable cardioverter-defibrillators. METHODS: We located 44 reports for which values of MAE incidence and predictive accuracy could be inferred: signal-averaged electrocardiography; heart rate variability; severe ventricular arrhythmia on ambulatory electrocardiography; left ventricular ejection fraction; and EPS. A meta-analysis of reports used receiver-operating characteristic curves to estimate mean values for sensitivity and specificity for each test and 95% confidence limits. We then simulated a clinical situation in which risk was estimated by combining tests in three stages. RESULTS: Test sensitivities ranged from 42.8% to 62.4%; specificities from 77.4% to 85.8%. A three-stage stratification yielded a low-risk group (80.0% with a two-year MAE risk of 2.9%), a high-risk group (11.8% with a 41.4% risk) and an unstratified group (8.2% with an 8.9% risk equivalent to a two-year incidence of 7.9%). CONCLUSIONS: Sensitivities and specificities for the five tests were relatively similar. No one test was satisfactory alone for predicting risk. Combinations of tests in stages allowed us to stratify 91.8% of patients as either high-risk or low-risk. These data suggest that a large prospective study to develop a robust prediction model is feasible and desirable.

Death, Sudden, Cardiac↗

PubMed2001

Role of brain natriuretic peptide in risk stratification of patients with congestive heart failure.

OBJECTIVES: Using a prospective study design, we assessed the value of brain natriuretic peptide (BNP) to identify patients with heart failure who have an increased risk of deterioration of their functional status. Furthermore, we examined the relationship between BNP and various clinical characteristics incorporated into an established survival model used for risk stratification. BACKGROUND: Prediction of the clinical course is a crucial part of the decision-making process about the adequate treatment strategy for patients with advanced congestive heart failure (CHF). Although laborious, multivariable indexes have been established for risk stratification, simple plasma BNP measurements may be as useful as prognostic indicators. METHODS: In 78 patients referred to our heart failure clinic, plasma BNP levels were compared with the results of a multivariable prognostic model. To assess the prognostic power of BNP, the clinical course of this cohort was monitored for a median follow-up period of 398 days. RESULTS: At study entry, plasma BNP and the heart failure survival score (HFSS) showed a significant correlation (r = -0.706). During follow-up, Kaplan-Meier estimates of freedom from clinical events differed significantly for patients above and below the 75th percentile concentrations of plasma BNP (p < 0.0001). Changes in plasma BNP were significantly related to changes in limitations of physical activity, as demonstrated by logistic regression analysis (chi-square statistic = 24.9, p < 0.0001). Proportional hazards analysis confirmed BNP as a powerful predictor of functional status deterioration (p < 0.0001). This prognostic information was as powerful as that derived from the multivariable HFSS. CONCLUSIONS: Measurement of plasma BNP concentrations might provide a useful and cost-effective screening tool that helps reduce the need and frequency for more expensive cardiac tests.

Activities of Daily Living↗

PubMed2003

Troponin: an important prognostic marker and risk-stratification tool in non-ST-segment elevation acute coronary syndromes.

Over the past decade, there has been a progressive evolution of cardiac marker testing in patients with acute coronary syndromes (ACS). This has not only resulted in a dramatic shift in how we view the diagnosis of myocardial infarction (MI), but it has also extended the role of cardiac marker testing into risk stratification and guidance of treatment decisions. By the year 2000, the development of highly sensitive and cardiac-specific troponin assays had resulted in a consensus change in the definition of MI, placing increased emphasis on cardiac-marker testing with troponins as the new gold standard. Furthermore, and perhaps more importantly, the role of the troponins as superior markers of subsequent cardiac risk in ACS patients became firmly established. Most recently, the supportive role of these markers in identifying patients with ACS who may derive particular benefit from potent anti-thrombotic and anti-platelet therapy or early invasive treatment strategies has been demonstrated. This paper will review the evolution of these important roles of troponin testing for risk stratification in ACS.

Biomarkers↗

PubMed1998

Value of pharmacologic stress echocardiography in risk stratification of patients with single-vessel disease: a report from the Echo-Persantine and Echo-Dobutamine International Cooperative Studies.

OBJECTIVES: This study sought to verify the effectiveness of pharmacologic stress echocardiography in risk stratification of patients with single-vessel disease. BACKGROUND: Noninvasive prognostic assessment of single-vessel disease is an unresolved issue to date. METHODS: The study evaluated prospectively collected data from 754 patients with angiographic single-vessel disease who underwent either dipyridamole (n = 576) or dobutamine (n = 178) stress echocardiography. Invasive treatment (coronary revascularization within 3 months of stress testing) was performed in 260 patients and medical treatment in 494. RESULTS: Echocardiographic positivity was observed in 421 patients (56%). Patients treated invasively had a higher incidence of stress test positivity (69% vs. 49%, p < 0.001) and left anterior descending coronary artery involvement (60% vs. 46%, p < 0.001) than patients maintained with medical therapy. During a mean follow-up of 37 months, 54 hard cardiac events occurred (14 deaths, 40 nonfatal infarctions): 37 in medically and 17 in invasively treated patients (7.5% vs. 6.5%, p = NS). On Cox analysis, a positive result on stress testing was the only independent prognostic predictor in medically treated patients (relative risk 2.92, 95% confidence interval 1.29 to 6.59). The 4-year infarction-free survival rate was higher for a negative than a positive stress test result in medically (93.9% vs. 87.3%, p = 0.009) but not invasively treated patients (92.7% vs. 97.1%, p = 0.545). Moreover, a significantly higher 4-year infarction-free survival rate was found in invasively versus medically treated patients with a positive (p = 0.012), but not in those with a negative, stress test result (p = 0.853). CONCLUSIONS: Pharmacologic stress echocardiography is effective in risk stratification of single-vessel disease and can accurately discriminate patients in whom coronary revascularization can have the maximal beneficial effect. These findings have a potential favorable impact on the cost-effectiveness of invasive procedures.

Coronary Artery Bypass↗

PubMed2003

Mechanistic stratification of antineuralgic agents.

Current treatment options in neuropathic pain include antidepressants, antiepileptics, antiarrhythmics, and analgesics. However, stratification of treatments based on their original therapeutic class is inadequate, as drugs belonging to a particular class may have distinct antineuralgic modes of action. It is therefore useful to review the mechanisms of action of these drugs and determine which of these mechanisms is most likely responsible for the drugs' efficacy in the symptomatic treatment of neuropathic pain. Switching from the traditional therapeutic class stratification to one based on putative antineuralgic mechanisms of action will allow more rational selection of therapies, and aid evaluation of the additive or synergistic effects of drugs when used in combination.

Analgesics↗

PubMed2000

Risk stratification in hypertension: new insights from the Framingham Study.

Five decades of epidemiologic research have established that blood pressure elevation is a common and powerful contributor to all of the major cardiovascular diseases, including coronary disease, stroke, peripheral artery disease, renal disease, and heart failure. The common variety of hypertension designated benign essential hypertension was not shown to be either benign or essential. Although clinicians favor the diagnosis and treatment of hypertension in terms of diastolic blood pressure elevation and categoric cut points, epidemiologic data show a more important influence of systolic blood pressure, and a continuous, graded influence of blood pressure even within what is regarded as the normotensive range. An important revelation in epidemiologic hypertension research is that hypertension usually occurs in conjunction with other metabolically linked risk factors; therefore, less than 20% occurs in isolation. The other risk factors that tend to accompany hypertension include glucose intolerance, obesity, left ventricular hypertrophy, and dislipidemia (elevated total, LDL, and small dense LDL cholesterol levels, raised triglyceride, and reduced HDL cholesterol levels). Clusters of three or more of these additional risk factors occur at four times the rate expected by chance. This clustering is attributed to an insulin resistance syndrome promoted by abdominal obesity. The amount of risk factor clustering accompanying elevated blood pressure was observed to increase with weight gain. Based on Framingham Study data the prevalence of insulin resistance syndrome in the general population could be as high as 22% in men and 27% in women. Risk of coronary disease, the most common and most lethal sequel to hypertension, increased stepwise with the extent of risk factor clustering. Among persons with hypertension, about 40% of coronary events in men and 68% in women are attributable to the presence of two or more additional risk factors. Only 14% of coronary events in hypertensive men and 5% of those in hypertensive women occurred in the absence of additional risk factors. Other important features of risk stratification of hypertension are the presence of an elevated heart rate and left ventricular hypertrophy, and an elevated fibrinogen that often accompany hypertension. Recent population-based data reported suggest that elevated renin accompanying hypertension may independently enhance the risk of coronary events. Because clustering of other major risk factors with hypertension is the rule, the prudent physician should routinely screen for the presence of these other factors. Multivariate risk assessment profiles are now available for coronary disease, stroke, peripheral artery disease, and heart failure, to enable physicians to pool all the relevant risk factor information so as to arrive at a composite risk estimate. Hypertensive patients are more appropriately targeted for therapy by such risk stratification and the goal of the therapy should be to improve the multivariate risk profile.

Adolescent↗

PubMed1993

Cardiac risk stratification using dipyridamole myocardial perfusion imaging and ambulatory ECG monitoring prior to vascular surgery.

Both dipyridamole myocardial perfusion imaging (cardiolite) and ambulatory ECG monitoring (Holter) for silent ischaemia have been found to be useful for stratification of cardiac risk in patients undergoing vascular surgery. The purpose of this study was to compare the diagnostic accuracy of these two non-invasive tests for prediction of perioperative cardiac events. One hundred patients (86 males, 14 females; mean age 67 +/- 8 years) underwent out-patient 48 h Holter monitoring and cardiolite imaging prior to vascular surgery (70 abdominal aortic aneurysm, 21 aortobifemoral, nine femoralpopliteal grafts). Ischaemia on Holter was defined as one or more episodes of ST segment depression 1 mm or greater, lasting 1 min or longer. Myocardial perfusion imaging was carried out with the high dose dipyridamole protocol (0.84 mg/kg), cardiolite and planar imaging. Ischaemia was defined as a segmental perfusion abnormality following dipyridamole with improved perfusion on rest imaging. Holter was positive for ischaemia in 34/100 patients (34%). Cardiolite scans were positive for ischaemia in 30/100 patients (30%). Perioperative myocardial infarction occurred in nine patients (two cardiac deaths). [table: see text] The diagnostic accuracy of the two tests was similar, with a low positive predictive value of 15-20%, and an extremely high negative predictive value of 94-96%. The event rate in patients with both tests negative was 2/48 (4.2%), with only one test positive 3/40 (7.5%) and with both tests positive 4/12 (33%). A reasonable approach to risk stratification would be to obtain either a Holter or cardiolite scan initially.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1999

Pharmaceutically-based severity stratification of an asthmatic population.

Algorithms designed to precisely identify disease severity for a given patient within a managed care population are helpful in organizing targeted interventions. These algorithms are also attracting considerable attention within the medical research community. Several health risk screening instruments have been developed; however, these involve survey methodologies and have several shortcomings. We present a valid and efficient method for predicting healthcare resource utilization among asthmatics in an Health Maintenance Organization (HMO) population. First, various diagnosis, procedure and pharmacy billing codes were used to identify the asthmatics within the database. The screening algorithm awards points each time one of these codes is identified for an HMO member. By varying the number of points necessary to consider a patient asthmatic, the sensitivity, specificity, positive and negative predictive values of the algorithm can be adjusted. Once identified as asthmatic, subjects were then stratified into severity levels based on pharmacy data. Severity stratification was validated directly by measuring asthma-related bed days utilized during the 12 months following the date of stratification. Our identification algorithm estimated an asthma prevalence of 3.84% within the studied population, with age-specific prevalence estimates that closely mirrored previously published survey data. There was a monotonic relationship between pharmacy severity levels and inpatient resource utilization. For example, asthmatics in severity level 1 used only 92 hospital days per 1000 asthmatics in the year following characterization, while those in levels 2-5 used 133, 156, 277 and 1168 hospital days (P < 0.001), respectively. Results from this model can be used as adjusters in other predictive models or stand alone to represent a patient's severity of illness.

Adolescent↗

PubMed2002

Stratification of solids, nitrogen and phosphorus in swine manure in deep pits under slatted floors.

Manure slurries stored in pits under slatted floors of both finishing and nursery barns were sampled at four different depths to study stratifications of total solids (TS) and nutrients (nitrogen and phosphorus), and to determine the relationship between the stratification of TS and nutrients. The results obtained can be used to improve the management and handling of swine manure in the under-slat storage pits. A management scheme that can be adopted for both the finishing and the nursery barns' pits is the layer-by-layer harvesting of the manure. The thinner manure, which is lower in nutrients, can be spread on land near the production units in larger volumes or it may pumped to land remote from the production units without causing many clogging problems. The thicker manure, higher in nutrients, can be transported to land further away and spread in smaller volumes. The TS content of each stratum can be used to accurately estimate the nitrogen and phosphorus levels in the respective strata so that application rates can easily be adjusted accordingly during the time of land application.

Age Factors↗

PubMed2003

An evaluation of existing risk stratification models as a tool for comparison of surgical performances for coronary artery bypass grafting between institutions.

OBJECTIVE: Risk stratification systems are used in cardiac surgery to estimate mortality risk for individual patients and to compare surgical performance between institutions or surgeons. This study investigates the suitability of six existing risk stratification systems for these purposes. METHODS: Data on 5471 patients who underwent isolated coronary artery bypass grafting at two UK cardiac centres between 1993 and 1999 were extracted from a prospective computerised clinical data base. Of these patients, 184 (3.3%) died in hospital. In-hospital mortality risk scores were calculated for each patient using the Parsonnet score, the EuroSCORE, the ACC/AHA score and three UK Bayes models (old, new complex and new simple). The accuracy for predicting mortality at an institutional level was assessed by comparing total observed and predicted mortality. The accuracy of the risk scores for predicting mortality for a patient was assessed by the Hosmer-Lemeshow test. The receiver operating characteristic (ROC) curve was used to evaluate how well a system ranks the patient with respect to their risk of mortality and can be useful for patient management. RESULTS: Both EuroSCORE and the simple Bayes model were reasonably accurate at predicting overall mortality. However predictive accuracy at the patient level was poor for all systems, although EuroSCORE was accurate for low to medium risk patients. Discrimination was fair with the following ROC areas: Parsonnet 0.73, EuroSCORE 0.76, ACC/AHA system 0.76, old Bayes 0.77, complex Bayes 0.76, simple Bayes 0.76. CONCLUSIONS: This study suggests that two of the scores may be useful in comparing institutions. None of the risk scores provide accurate risk estimates for individual patients in the two hospitals studied although EuroSCORE may have some utility for certain patients. All six systems perform moderately at ranking the patients and so may be useful for patient management. More results are needed from other institutions to confirm that the EuroSCORE and the simple Bayes model are suitable for institutional risk-adjusted comparisons.

Bayes Theorem↗