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PubMed2006

Objective quality evaluation of fluorescence images to optimize automatic image acquisition.

BACKGROUND: Because different spectral sensitivities of human eye and image sensor lead to different perception of fluorescence signals, data generation is an important step in image analysis, because following work steps depend on it. METHODS: We developed a method to determine image parameters allowing an objective appraisal of quality of image data as well as a separation of object and background. RESULTS: Calculated parameters can be used for an automated adjustment of camera parameters in image analysis systems. DISCUSSION: Our approach for objective adjusted data generation achieves an improvement of analysis quality.

Cell Line, Tumor↗
PubMed1975

Ragweed pollen generation and sampling methods for filtration studies.

The means of generating and measuring the concentration of ragweed pollen particles for air filtration studies is discussed. The development of an inexpensive in-line impaction type sampler which collects the sample on filter paper is described. The advantages of the total particle count method when using this sampler are also defined. The effect of sampling an air steam without using an isokinetic probe was investigated; a non isokinetic sampling train was found to give results with accuracy comparable to isokinetic data. Another part of the study was to examine the "shadowing" effect of one sampling probe. Means are given for adjusting data for this effect.

Filtration↗
PubMed1995

Ethanol-induced anesthesia in inbred strains of long-sleep and short-sleep mice: a genetic analysis of repeated measures using censored data.

We present a repeated-measures, genetic analysis of ethanol-induced anesthesia (sleep time) in mice from the inbred long-sleep (ILS) and short-sleep (ISS) strains of mice and their derived F1 and F2 generations. Mice (total N > 1300) were administered a 4.1 g/kg intraperitoneal dose of ethanol at two times, 7 to 10 days apart. A method suggested by Cohen was used to analyze the resulting data, which contained a known number of unmeasured observations. A genetic model that included both additive and epistatic parameters fitted the adjusted data well. A novel procedure for estimating heritability, based on a comparison of repeatability coefficients from the isogenic and genetically segregating populations, was also employed. Results of this analysis suggested that the heritability for individual measurements of sleep time is about .30, whereas the heritability of average scores is about .40. Results of this analysis also confirm that the ILS and ISS strains differ for genes at seven or more loci that influence sleep time. Since the ILS and ISS were derived by inbreeding the LS and SS lines, these results further suggest that almost all of the genetic variation present in the selected lines have been maintained in the ILS and ISS strains.

Animals↗
PubMed2001

Predicting admission rates to secure forensic psychiatry services.

BACKGROUND: The planning and development of secure forensic psychiatry services for mentally disordered offenders in England and Wales has proceeded independently within different regional areas. However, certain mental disorders, offenders, and offending behaviour are all more prevalent in geographical areas characterized by socio-economic deprivation and social disorganization. Failure to consider these factors has led to inadequate service provision in some areas and inequity in funding. A new model is required to predict admissions to these services as an aid to resource allocation. METHOD: Actual admissions (N = 3155) to high and medium secure psychiatric services for seven of 14 (pre-reorganization) Regional Health Authorities, 1988-94. Expected admissions were calculated for each district using 1991 census data adjusted for under-enumeration. Standardized psychiatric admission ratios were calculated and a range of social, health status, and service provision data were used as explanatory variables in a regression analysis to determine variation between districts. RESULTS: Actual psychiatric admissions varied from 160% above to 62% below expected for age, sex, and marital status, according to patients' catchment area of origin, measured according to deciles of the distribution of underprivileged area scores at ward level. The most powerful explanatory variables included a composite measure of social deprivation, ethnicity and availability of low secure beds at regional level. CONCLUSION: Admission rates to secure forensic psychiatry services demonstrate a linear correlation with measures of socio-economic deprivation in patients catchment area of origin. A model was developed to predict admissions from District Health Authorities and is recommended for future use in resource allocation. Identification of factors that explain higher admission rates of serious offenders with mental disorder from deprived areas is a priority for future research.

Adult↗
PubMed2004

The costs of decedents in the Medicare program: implications for payments to Medicare + Choice plans.

OBJECTIVE: To discuss and quantify the incentives that Medicare managed care plans have to avoid (through selective enrollment or disenrollment) people who are at risk for very high costs, focusing on Medicare beneficiaries in the last year of life-a group that accounts for more than one-quarter of Medicare's annual expenditures. DATA SOURCE: Medicare administrative claims for 1994 and 1995. STUDY DESIGN: We calculated the payment a plan would have received under three risk-adjustment systems for each beneficiary in our 1995 sample based on his or her age, gender, county of residence, original reason for Medicare entitlement, and principal inpatient diagnoses received during any hospital stays in 1994. We compared these amounts to the actual costs incurred by those beneficiaries. We then looked for clinical categories that were predictive of costs, including costs in a beneficiary's last year of life, not accounted for by the risk adjusters. DATA EXTRACTION METHODS: The analyses were conducted using claims for a 5 percent random sample of Medicare beneficiaries who died in 1995 and a matched group of survivors. PRINCIPAL FINDINGS: Medicare is currently implementing the Principal Inpatient Diagnostic Cost Groups (PIP-DCG) risk adjustment payment system to address the problem of risk selection in the Medicare+Choice program. We quantify the strong financial disincentives to enroll terminally ill beneficiaries that plans still have under this risk adjustment system. We also show that up to one-third of the selection observed between Medicare HMOs and the traditional fee-for-service system could be due to differential enrollment of decedents. A risk adjustment system that incorporated more of the available diagnostic information would attenuate this disincentive; however, plans could still use clinical information (not included in the risk adjustment scheme) to identify beneficiaries whose expected costs exceed expected payments. CONCLUSIONS: More disaggregated prospective risk adjustment methods and alternative payment systems that compensate plans for delivering care to certain classes of patients should be considered to ensure access to high-quality managed care for all beneficiaries.

Actuarial Analysis↗
PubMed2001

Thrombosis in Behçet's disease: a retrospective survey from a single UK centre.

OBJECTIVE: To contribute to knowledge of vascular occlusion in Behçet's disease (BD), prevalence and relative risk for thrombosis were ascertained retrospectively in a cohort of Caucasian patients with the disease. PATIENTS: The study included 73 BD patients (36 males, 37 females, mean age 45+/-11 yr) attending the Immunology/Rheumatology Department of Northwick Park Hospital. A group of 146 patients without BD, attending the same department, served as a control group. RESULTS: Thrombosis was more frequent in BD patients than in controls (23/73, 32% vs 7/146, 5%, P<0.001). This was accounted for by a higher prevalence of venous thrombosis in BD patients (18/73, 25% vs 4/146, 3%, P<0.001). Gender-adjusted data revealed an 11-fold risk of developing any thrombosis and a 14-fold risk of developing venous thrombosis in BD. After adjusting for differences in age at first symptoms, male BD patients showed a 6-fold higher risk of vein thrombosis. Males reported more often thrombophlebitis (13/36, 36% vs 0/0, P<0.001), folliculitis (8/36, 22% vs 1/37, 3%, P<0.01) and retinal vasculitis (13/36, 36%, vs 4/37, 11%, P=0.01) than females, in whom arthralgia prevailed (23/37, 62%, vs 12/36, 33%, P=0.01). CONCLUSION: In our population, BD confers a 14-fold risk of developing venous thrombosis. The risk is sixfold higher in male BD patients, who fare worse than females with regard to thrombophlebitis, folliculitis and retinal vasculitis.

Behcet Syndrome↗
PubMed1993

Effect of intravenous immunoglobulin (IVIG) on CD4+ lymphocyte decline in HIV-infected children in a clinical trial of IVIG infection prophylaxis. The National Institute of Child Health and Human Development Intravenous Immunoglobulin Clinical Trial Study Group.

Our objective was to evaluate the effect of intravenous immunoglobulin (IVIG) on absolute CD4+ lymphocyte count (CD4+ count) trends in human immunodeficiency virus- (HIV) infected children enrolled in a trial of IVIG for infection prophylaxis. To that end, we conducted a randomized, double-blind, outpatient trial comparing subjects treated with 400 mg per kilogram of IVIG every 28 days with those given 0.1% albumin placebo. CD4+ counts were measured at entry and every 12 weeks. Twenty-eight clinical centers in mainland United States and Puerto Rico participated. Previous reports showed IVIG efficacy for infection prophylaxis in 313 patients with entry CD4+ counts of > or = 0.20 x 10(9)/L (> or = 200/mm3). Two hundred and seventy-seven (89%) of these 313 children had three or more CD4+ counts measured during the trial and were included in evaluation of CD4+ count trends. Rates of CD4+ count decline, as measured by regression slopes, were compared between IVIG and placebo groups using generalized linear models, comparing unadjusted, age-adjusted, and standardized age-adjusted data. Potential covariate effects were assessed by modeling change in CD4+ count in terms of log change between successive measurements. Age-adjusted slope analysis showed slowing of CD4+ count decline by 13.5 cells/mm3 per month in IVIG compared with placebo recipients (95% confidence interval, 3.1-23.9, p = 0.012). Modeling log change between measurements documented a beneficial effect of IVIG that was cumulative over time and independent of other therapies. Occurrence of serious bacterial infection in the interval before CD4+ count measurement or death was independently associated with more rapid CD4+ count decline (p = 0.01 and p = 0.008, respectively). Zidovudine therapy was associated with a transient increase in CD4+ count. Benefits of IVIG include slowing of CD4+ count decline as well as previously reported reductions in serious and minor bacterial and viral infections in subjects with entry CD4+ counts of > or = 0.20 x 10(9)/L. This finding provides corroboration for the hypothesis that immunologic mechanisms contribute to the pathogenesis of CD4+ decline in HIV infection.

Age Factors↗
PubMed2005

Adjusting EEG coherence for inter-electrode distance effects: an exploration in normal children.

Electroencephalographic (EEG) coherence between two points is strongly related to the distance between them, being inflated by volume conduction effects at short distances and reduced by signal phase differences at larger distances. This precludes simple comparison of coherence estimates involving different inter-electrode distances. We investigated adjusting coherence measures to remove such distance effects. After subtracting the estimated effects of random coherence due to volume conduction, exponential regression of the reduced coherence values against measured inter-electrode distance was used to estimate the remaining effects of inter-electrode distance. Residuals from this procedure were taken as coherences corrected for the systematic distance effects. These were adjusted to the mean reduced coherence level to avoid complexities in conceptualising negative residual coherences. It was found that systematic inter-electrode distance effects accounted for more than 50% of the variance remaining after removal of random coherence estimates. After these were also removed, substantial effects of EEG frequency band, different regions of the brain, and interhemispheric versus intrahemispheric values, as well as laterality effects within the latter, were obtained. Regional and frequency differences in adjusted coherence appear to reflect patterns expected from normal cortical development, but detailed understanding of more complex interactive effects is limited by the lack of relevant developmental data. Adjusting coherence values to remove systematic variability due to inter-electrode distances better represents cortico-cortical coupling and allows more efficient statistical analysis. This may contribute towards a better integration of coherence data in the EEG exploration of both normal and atypical brain functioning.

Brain↗
PubMedDate not supplied

Mainstream Experiences for Learning Disabled students (Project MELD): preliminary report.

Mainstream Experiences for the Learning Disabled (MELD) was developed to accommodate students with learning disabilities in the mainstream. This article reports the progress of 13 students at the end of 1 year of planning and 1 year of implementing the MELD model in one urban elementary school. Observational and school adjustment data from the implementation year suggest that although the MELD model was not fully incorporated into the mainstream classes, students with learning disabilities adjusted well to a less individualized and more demanding mainstream program. They came to school regularly, did not present serious behavior problems, and spent as much of reading class and more of math class on task as they had in special education. These students in the mainstream were assigned more opportunities to work with text materials rather than workbooks in reading and spent significantly more reading time in teacher-directed lessions. Nevertheless, the students made no significant progress in reading or math and earned lower grades during the implementation year. The authors suggest that students with learning disabilities will not succeed in the mainstream if teachers continue "business as usual" in mainstream classes.

Achievement↗
PubMed2026

Risk prediction in patients with heart failure with preserved ejection fraction: the LIFE-Preserved model.

BACKGROUND AND AIMS: Heart failure (HF) with preserved ejection fraction (HFpEF) constitutes a heterogeneous disease with varying prognosis. Given the rising incidence of HFpEF, accurate risk prediction for these patients is needed to identify high-risk individuals, who may benefit the most from preventive treatments. The LIFE-Preserved model was developed and validated for the prediction of individual short-term and lifetime risk for HF hospitalization or cardiovascular (CV) death in patients with HFpEF. METHODS: LIFE-Preserved was derived in 20 332 patients aged 40-90 years with a left ventricular ejection fraction &#x2265; 50% from the Swedish HF Registry. Cause- and sex-specific Cox models were derived to predict the risk of HF hospitalization or CV death using 14 routinely available predictors. Use of age as the timescale allowed for predictions beyond the maximum follow-up duration in the derivation data, adjusted for competing risks. External validation was performed in two trials (EMPEROR-Preserved and TOPCAT-Americas) and three registries (NHS England Secure Data Environment, Veterans Affairs, and HF-Particles). Model performance was assessed by discrimination and calibration. RESULTS: During a median follow-up of 1.8 years (interquartile range .6-4.2, maximum 19 years), 9341 first HF hospitalizations or CV deaths (46%) were observed in Swedish HF Registry. External validation included data from 28 062 patients with HFpEF [9930 (35%) first HF hospitalizations or CV deaths]. Pooled C-statistics were .714 (95% confidence interval .652-.775) in trials and .658 (95% confidence interval .599-.717 in registries, with adequate calibration in all external validation sources. Performance was similar in men and women. An interactive calculator of the LIFE-Preserved model has been made available here. CONCLUSIONS: The LIFE-Preserved model enables prediction of short-term and lifetime risk of HF hospitalization or CV death in patients with HFpEF. The model could serve as a tool to identify high-risk HFpEF patients, guiding clinical management and shared decision-making.

Humans↗
PubMed1994

Sexuality and the older person with cancer.

PURPOSE/OBJECTIVES: To review the particular needs of older patients with cancer with respect to sexuality and to present appropriate nursing strategies to facilitate adjustment. DATA SOURCES: Books, journals, and American Cancer Society publications. DATA SYNTHESIS: Physical and emotional changes caused by diagnosis and treatment of cancer often are compounded in the older patient. Of particular concern is sexual adjustment, which already may be compromised by the effects of aging on normal sexual functioning, absence of a partner, or personal/societal prohibitions against sexuality in this population. CONCLUSIONS: Exercise, nutrition, and self-esteem intervention programs, coupled with strategies to facilitate sexual activity that take into account normal aging, can help older patients with cancer to reestablish usual sexual functioning. IMPLICATIONS FOR NURSING PRACTICE: Nurses must establish a comfort level with sexual assessment and patient intervention so that they can provide counseling and suggest appropriate interventions.

Adaptation, Psychological↗
PubMed2006

Unravelling in vitro variables of major importance for the outcome of mass spectrometry-based serum proteomics.

The use of mass spectrometry (MS) for analysing low-molecular weight proteins and peptides from biological fluids has a great, yet not fully realized, potential for biomarker discovery. To prune MS-data as much as possible for non-relevant non-biological variation the development of standardized protocols for handling and processing the samples before MS and adjusting data after MS to compensate for method-induced variability are warranted. This calls for knowledge about how different variables contribute to MS-based proteome analyses. In addition, identification of the peptides involved in pre-analytical variation will be helpful in evaluating the clinical significance of predictive models derived from MS data. Using human sera, extraction by weak cation-exchange magnetic beads, and analysis by MALDI-TOF MS we here evaluated pre-analytical variation and identify peptides involved in this. The influences of humidity, temperature, and time for preparation of sera on spectral changes were evaluated. Also, the reproducibility of the methods and the effect of a baseline correction procedure were examined. Low temperatures, short handling times, and a baseline correction procedure minimize the contribution of artifacts to sample variability as observed by MS. The complement split product C3f and fragments thereof appear to be sensitive indicators of sample handling induced modifications. Other peptides that are indicative of such variability are fibrin and kininogen fragments. Using strict experimental guidelines as well as standardized sample collection procedures it is possible to obtain reproducible peak intensities and positions in serum mass profiling using magnetic bead-based fractionation and MALDI-TOF MS.

Biomarkers↗
PubMed1998

Second metacarpal midshaft geometry in an historic cemetery sample.

Study of bone mass at the second metacarpal midshaft has contributed to our understanding of skeletal growth and aging within and between populations and has relied extensively on noninvasive techniques and in particular radiogrammetric data. This study reports age, sex, and side variation in size and shape data acquired from direct measurement of cross-sections obtained from a large (n = 356), homogeneous skeletal sample. Correlation analysis and three-way ANOVA of size-adjusted data confirm general impressions of patterned variation in this element: males have absolutely but not necessarily relatively larger bones than females; the right side is larger than the left, though a larger than expected proportion (approximately 25%) of left metacarpals exhibits greater values than the right; and bone mass but not strength (in males) declines with age. Contrary to the widely accepted assumption of circularity for this location, direct measurement of cross-sectional geometry confirms previous biplanar radiogrammetric conclusions regarding the noncircularity of the second metacarpal midshaft and identifies a significant difference between males and females, with the latter having a more cylindrical diaphysis. Deviation of the axes of maximum and minimum bending strength associated with noncircularity suggests a distribution of bone mass to resist bending moments perpendicular to the distal palmar arch, though this conclusion awaits more robust study of the functional anatomy of the metacarpal diaphysis.

Adult↗
PubMed2005

Physician supply, treatment, and amputation rates for peripheral arterial disease.

OBJECTIVE: To test whether the availability of vascular surgeons and interventional radiologists in a region affects revascularization and amputation rates for patients with peripheral arterial disease (PAD). METHODS: We identified all patients with PAD in the Medicare claims database in 1994 and tracked their claims through 1999. We aggregated risk-adjusted data on the 143,202 patients who survived through 1999 by Hospital Referral Region and merged this data with information on local physician supply and other regional characteristics. Instrumental variables analysis was used to account for unobserved illness severity. Main outcome measures were risk-adjusted rates of lower extremity bypass surgery, angioplasty, and amputation by region. RESULTS: Increasing vascular surgeon supply in a region by approximately one standard deviation (.30/10,000 Medicare beneficiaries) is associated with a 0.9 percentage point increase in bypass surgery rates and a 1.6 percentage point reduction in amputation rates. We find weaker evidence that greater availability of interventional radiologists increases angioplasty rates and reduces amputation rates. Factors reflecting regional attractiveness, such as the rating of a region based on climate, recreation, crime, and other attributes, were strong independent predictors of the number of vascular surgeons and interventional radiologists in an area. CONCLUSIONS: Availability of specialists affects outcomes for PAD patients. Regional variability in specialists who treat PAD is influenced by factors other than regional medical needs. Policies aimed at increasing the supply of vascular surgeons and interventional radiologists and their provision of bypass surgery in underserved areas may help to reduce regional disparities in amputation.

Aged↗
PubMed2005

Cholesterol tracking from childhood to adult mid-life in children from the Busselton study.

AIM: To determine if subjects' cholesterol levels tracked relative to their peers from early childhood to adult mid-life. METHODS: Longitudinal study using subjects from the Busselton Population Study. Data were available from 1967 on a triennial basis until 1983, and a re-survey held in 1994. The study included 1764 subjects aged 5-18 y at first measurement. Pearson's correlation coefficient, adjusted for age and survey year, was used to examine cholesterol tracking. The proportion of children who persisted with cholesterol measurements in the extreme high quartile was assessed over time before and after adjusting data for regression to the mean. The variability of the children's cholesterol level was examined by track width using the method of Porkka. RESULTS: The correlation coefficients for tracking were from 0.35 to 0.55. Stronger correlations coincided with shorter time periods between measurements. Before adjustment for regression to the mean, 55-60% of children from the highest quartile at first measurement remained in the same quartile 27 y later. After adjustment for regression to the mean, the number of children with levels in the extreme high quartile decreased, but 80% of these persisted in that quartile. CONCLUSION: Intra-individual variations in cholesterol levels have an important influence on population tracking levels and need to be considered when interpreting tracking results from early childhood to adult mid-life. However, removing the effect of regression to the mean by taking multiple measurements of cholesterol will probably improve prediction for individuals.

Adolescent↗
PubMed2001

Dietary assessment in Whitehall II: comparison of 7 d diet diary and food-frequency questionnaire and validity against biomarkers.

The aim of the present cross-sectional study was to examine the agreement and disagreement between a 7 d diet diary (7DD) and a self-administered machine-readable food-frequency questionnaire (FFQ) asking about diet in the previous year, and to validate both methods with biomarkers of nutrient intake. The subjects were an age- and employment-grade-stratified random subsample of London-based civil servants (457 men and 403 women), aged 39-61 years, who completed both a 7DD and a FFQ at phase 3 follow-up (1991-1993) of the Whitehall II study. Mean daily intakes of dietary energy, total fat, saturated, monounsaturated and polyunsaturated fatty acids, linoleic acid, total carbohydrate excluding fibre, sugars, starch, dietary fibre, protein, vitamin C, vitamin E (as alpha-tocopherol equivalents), folate, carotenes (as total beta-carotene activity), Fe, Ca, Mg, K and alcohol were measured. Serum cholesteryl ester fatty acids (CEFA), plasma alpha-tocopherol and beta-carotene were also measured as biomarkers. Estimates of mean energy intake from the two methods were similar in men, and some 10 % higher according to the FFQ in women. Compared with the 7DD, the FFQ tended to overestimate plant-derived micronutrient intakes (carotenes from FFQ v. 7DD men 2713 (SD 1455) v. 2180 (SD 1188) microg/d, women 3100 (SD 1656) v. 2221 (SD 1180) microg/d, both differences P<0.0001) and to underestimate fat intake. Against plasma beta-carotene/cholesterol, carotene intake was as well estimated by the FFQ as the 7DD (Spearman rank correlations, men 0.32 v. 0.30, women 0.27 v. 0.22, all P< or =0.0001, energy-adjusted data). Ranking of participants by other nutrient intakes tended to be of the same order according to the two dietary methods, e.g. rank correlations for CEFA linoleic acid against FFQ and 7DD estimates respectively, men 0.38 v. 0.41, women 0.53 v. 0.62, all P< or =0.0001, energy-adjusted % fat). For alpha-tocopherol there were no correlations between plasma level and estimated intakes by either dietary method. Quartile agreement for energy-adjusted nutrient intakes between the two self-report methods was in the range 37-50 % for men and 32-44 % for women, and for alcohol, 57 % in both sexes. Disagreement (misclassification into extreme quartiles of intake) was in the range 0-6 % for both sexes. The dietary methods yielded similar prevalences (about 34 %) of low energy reporters. The two methods show satisfactory agreement, together with an expected level of systematic differences, in their estimates of nutrient intake. Against the available biomarkers, the machine-readable FFQ performed well in comparison with the manually coded 7DD in this study population. For both methods, regression-based adjustment of nutrient intake to mean dietary energy intake by gender appears on balance to be the optimal approach to data presentation and analysis, in view of the complex problem of low energy reporting.

Adult↗
PubMed2004

Underestimation of risk due to exposure misclassification.

Exposure misclassification constitutes a major obstacle when developing dose-response relationships for risk assessment. A non-differentional error results in underestimation of the risk. If the degree of misclassification is known, adjustment may be achieved by sensitivity analysis. The purpose of this study was to examine the full magnitude of measurement error in determining the prenatal exposure to methylmercury. We used data from a prospective study of a Faroese birth cohort. Two biomarkers of methylmercury exposure were available, i.e., the mercury concentrations in cord blood and in maternal hair (sampled at the time of parturition). The laboratory imprecision on both chemical analyses was thought to be below 5% coefficient of variation (CV). As a third exposure parameter, we used the dietary questionnaire response on frequency of whale meat dinners. Factor analysis and structural equation analysis were applied to assess the full extent of the imprecision. The calculated total imprecision much exceeded the known laboratory variation: the CV was 28-30% for the cord-blood concentration and 52-55% for the maternal hair concentration. The dietary questionnaire response was even more imprecise. These findings illustrate that measurement error may be greatly underestimated if judged solely from reproducibility or laboratory quality data. Adjustment by sensitivity analysis is meaningful only if realistic measurement errors are applied. When exposure measurement errors are overlooked or underestimated, decisions based on the precautionary principle will not appropriately reflect the degree of precaution that was intended.

Biomarkers↗
PubMed2004

Predicting resource utilization in a Veterans Health Administration primary care population: comparison of methods based on diagnoses and medications.

BACKGROUND: Valid methods of predicting resource utilization in primary care populations are needed. We compared the predictive validity of a method based on diagnoses from administrative data (Adjusted Clinical Groups [ACGs]) and a method using medication profiles (Chronic Disease Index [CDI]). METHODS: This retrospective cohort study included 31,212 primary care patients in a Veterans Health Administration (VA) network who received outpatient medication prescriptions in 1999 and who had VA utilization in 1999 and 2000. ACG and CDI classifications were determined using 1999 data. Analyses compared the predictive validity with respect to outpatient clinic visits and days of hospital care. RESULTS: Both ACGs and CDI explained a higher proportion of the variance in outpatient visits than demographic data alone. However, explained variance was higher for ACGs. For example, ACGs explained 30.2% of the variance in total visits in 1999, compared with 8.8% for the CDI. Results were similar for 2000, although the explained variance declined for both methods (eg, 16.3% and 5.7%, respectively, for total visits). Results were similar in analyses examining the discrimination of the 2 methods to predict hospital use; for example, c statistics for ACGs and CDI scores were 0.86 versus 0.70, respectively (P <0.05), for 1999 and 0.72 and 0.65, respectively (P <0.05), for 2000. CONCLUSION: Among VA patients, ACGs had superior predictive validity than the CDI, a newer nonproprietary method based on pharmacy data. The findings suggest that diagnosis-based measures could be preferable for ambulatory case-mix adjustment and are valid across a wide range of populations.

Age Distribution↗