Medicare National Claims History Research Articles

Airborne Fine Particles and Risk of Hospital Admissions for Understudied Populations: Effects by Urbanicity and Short-Term Cumulative Exposures in 708 U.S. Counties.

Background:Evidence of health risks associated with ambient airborne fine particles in nonurban populations is extremely limited.Objective:We estimated the risk of hospitalization associated with short-term exposures to particulate matter with an aerodynamic diameter < 2.5 μm (PM2.5) in urban and nonurban counties with population ≥ 50,000.Methods:We utilized a database of daily cardiovascular- and respiratory-related hospitalization rates constructed from Medicare National Claims History files (2002–2006), including 28 million Medicare beneficiaries in 708 counties. Daily PM2.5 exposures were estimated using the Community Multiscale Air Quality (CMAQ) downscaler. We used time-series analysis of hospitalization rates and PM2.5 to evaluate associations between PM2.5 levels and hospitalization risk in single-pollutant models.Results:We observed an association between cardiovascular hospitalizations and same-day PM2.5 with higher risk in urban counties: 0.35% [95% posterior interval (PI): –0.71%, 1.41%] and 0.98% (95% PI: 0.73%, 1.23%) increases in hospitalization risk per 10-μg/m3 increment in PM2.5 were observed in the least-urban and most-urban counties, respectively. The largest association for respiratory hospitalizations, a 2.57% (95% PI: 0.87%, 4.30%) increase per 10-μg/m3 increase in PM2.5, was observed in the least-urban counties; in the most-urban counties, a 1.13% (0.73%, 1.54%) increase was observed. Effect estimates for cardiovascular hospitalizations were highest for smaller lag times, whereas effect estimates for respiratory hospitalizations increased as more days of exposure were included.Conclusion:In nonurban counties with population ≥ 50,000, exposure to PM2.5 is associated with increased risk for respiratory hospitalizations; in urban counties, exposure is associated with increased risk of cardiovascular hospitalizations. Effect estimates based on a single day of exposure may underestimate true effects for respiratory hospitalizations.Citation:Bravo MA, Ebisu K, Dominici F, Wang Y, Peng RD, Bell ML. 2017. Airborne fine particles and risk of hospital admissions for understudied populations: effects by urbanicity and short-term cumulative exposures in 708 U.S. counties. Environ Health Perspect 125:594–601; http://dx.doi.org/10.1289/EHP257

Canadian Forest Fires and the Effects of Long-Range Transboundary Air Pollution on Hospitalizations among the Elderly.

In July 2002, lightning strikes ignited over 250 fires in Quebec, Canada, destroying over one million hectares of forest. The smoke plume generated from the fires had a major impact on air quality across the east coast of the U.S. Using data from the Medicare National Claims History File and the U.S. Environmental Protection Agency (EPA) National air pollution monitoring network, we evaluated the health impact of smoke exposure on 5.9 million elderly people (ages 65+) in the Medicare population in 81 counties in 11 northeastern and Mid-Atlantic States of the US. We estimated differences in the exposure to ambient PM2.5-airborne particulate matter with aerodynamic diameter of ≤2.5 μm-concentrations and hospitalizations for cardiovascular, pulmonary and injury outcomes, before and during the smoke episode. We found that there was an associated 49.6% (95% confidence interval (CI), 29.8, 72.3) and 64.9% (95% CI, 44.3-88.5) increase rate of hospitalization for respiratory and cardiovascular diagnoses, respectively, when the smoke plume was present compared to before the smoke plume had arrived. Our study suggests that rapid increases in PM2.5 concentrations resulting from wildfire smoke can impact the health of elderly populations thousands of kilometers removed from the fires.

Coarse Particulate Matter Air Pollution and Hospital Admissions for Cardiovascular and Respiratory Diseases Among Medicare Patients

Health risks of fine particulate matter of 2.5 microm or less in aerodynamic diameter (PM2.5) have been studied extensively over the last decade. Evidence concerning the health risks of the coarse fraction of greater than 2.5 microm and 10 microm or less in aerodynamic diameter (PM10-2.5) is limited. To estimate risk of hospital admissions for cardiovascular and respiratory diseases associated with PM10-2.5 exposure, controlling for PM2.5. Using a database assembled for 108 US counties with daily cardiovascular and respiratory disease admission rates, temperature and dew-point temperature, and PM10-2.5 and PM2.5 concentrations were calculated with monitoring data as an exposure surrogate from January 1, 1999, through December 31, 2005. Admission rates were constructed from the Medicare National Claims History Files, for a study population of approximately 12 million Medicare enrollees living on average 9 miles (14.4 km) from collocated pairs of PM10 and PM2.5 monitors. Daily counts of county-wide emergency hospital admissions for primary diagnoses of cardiovascular or respiratory disease. There were 3.7 million cardiovascular disease and 1.4 million respiratory disease admissions. A 10-microg/m3 increase in PM10-2.5 was associated with a 0.36% (95% posterior interval [PI], 0.05% to 0.68%) increase in cardiovascular disease admissions on the same day. However, when adjusted for PM2.5, the association was no longer statistically significant (0.25%; 95% PI, -0.11% to 0.60%). A 10-microg/m3 increase in PM10-2.5 was associated with a nonstatistically significant unadjusted 0.33% (95% PI, -0.21% to 0.86%) increase in respiratory disease admissions and with a 0.26% (95% PI, -0.32% to 0.84%) increase in respiratory disease admissions when adjusted for PM2.5. The unadjusted associations of PM2.5 with cardiovascular and respiratory disease admissions were 0.71% (95% PI, 0.45%-0.96%) for same-day exposure and 0.44% (95% PI, 0.06% to 0.82%) for exposure 2 days before hospital admission. After adjustment for PM2.5, there were no statistically significant associations between coarse particulates and hospital admissions for cardiovascular and respiratory diseases.

Bile duct injury during cholecystectomy and survival in medicare beneficiaries.

Common bile duct (CBD) injury during cholecystectomy is a significant source of patient morbidity, but its impact on survival is unclear. To demonstrate the relation between CBD injury and survival and to identify the factors associated with improved survival among Medicare beneficiaries. Retrospective study using Medicare National Claims History Part B data (January 1, 1992, through December 31, 1999) linked to death records and to the American Medical Association's (AMA's) Physician Masterfile. Records with a procedure code for cholecystectomy were reviewed and those with an additional procedure code for repair of the CBD within 365 days were defined as having a CBD injury. Survival after cholecystectomy, controlling for patient (sex, age, comorbidity index, disease severity) and surgeon (procedure year, case order, surgeon specialty) characteristics. Of the 1 570 361 patients identified as having had a cholecystectomy (62.9% women), 7911 patients (0.5%) had CBD injuries. The entire population had a mean (SD) age of 71.4 (10.2) years. Thirty-three percent of all patients died within the 9.2-year follow-up period (median survival, 5.6 years; interquartile range, 3.2-7.4 years), with 55.2% of patients without and 19.5% with a CBD injury remained alive. The adjusted hazard ratio (HR) for death during the follow-up period was significantly higher (2.79; 95% confidence interval [CI]; 2.71-2.88) for patients with a CBD injury than those without CBD injury. The hazard significantly increased with advancing age and comorbidities and decreased with the experience of the repairing surgeon. The adjusted hazard of death during the follow-up period was 11% greater (HR, 1.11; 95% CI, 1.02-1.20) if the repairing surgeon was the same as the injuring surgeon. The association between CBD injury during cholecystectomy and survival among Medicare beneficiaries is stronger than suggested by previous reports. Referring patients with CBD injuries to surgeons or institutions with greater experience in CBD repair may represent a system-level opportunity to improve outcome.

Construct Validity of Medicare Chemotherapy Claims

The elderly are under represented in clinical trials of cancer therapy and the elderly who are enrolled may be unrepresentative. To assess whether Medicare claims data might be used to understand the benefits and tolerance of chemotherapy in the general elderly population, the construct validity of Medicare 5FU claims for elderly colon cancer patients within the SEER-Medicare data set was determined. In this validation study of Medicare chemotherapy claims from the linked the SEER-Medicare data set, the patterns of 5FU chemotherapy claims were evaluated for an incident cohort of elderly colon cancer patients (n = 15,039) during the 13 months following their diagnosis. Patterns of Medicare National Claims History (NCH) 5FU claims were evaluated with respect to prespecified patient-level disease and demographic factors from the data set. Twenty-two percent of patients had at least one detectable 5FU claim during the observation period. Among those patients, the median dose of 5FU was 1000 mg, the median interval between 5FU claims was 7 days, and the median number of claims during this period was 24. Multivariate regression revealed expected associations between demographic and disease factors and the likelihood of having a Medicare NCH 5FU claim. With increasing cancer stage, patients' likelihood of having a 5FU claim increased. Younger patients, married patients, white patients, patients with low comorbidity, and patients living in urban and less impoverished regions were each more likely to have 5FU claims. Because their pattern is consistent with the standard of medical care and with previously described associations with disease and demographic factors, it was concluded that Medicare NCH claims for 5FU administration in the SEER-Medicare data set exhibit construct validity. Criterion validation studies with an external gold standard should be pursued to determine the sensitivity and specificity of chemotherapy codes in the Medicare NCH files.

Relation between operator and hospital volume and outcomes following percutaneous coronary interventions in the era of the coronary stent.

Studies have found an association between physician and institution procedure volume for percutaneous coronary interventions (PCIs) and patient outcomes, but whether implementation of coronary stents has allowed low-volume physicians and centers to achieve outcomes similar to their high-volume counterparts is unknown. To assess the relationship between physician and hospital PCI volumes and patient outcomes following PCIs, given the availability of coronary stents. Analysis of data from Medicare National Claims History files for 167 208 patients aged 65 to 99 years who had PCIs performed by 6534 physicians at 1003 hospitals during 1997. Of these procedures, 57.7% involved coronary stents. Rates of coronary artery bypass graft (CABG) surgery and 30-day mortality occurring during the index episode of care, stratified by physician and hospital PCI volume. Overall unadjusted rates of CABG during the index hospitalization and 30-day mortality were 1.87% and 3.30%, respectively. After adjustment for case mix, patients treated by low-volume (<30 Medicare procedures) physicians had an increased risk of CABG vs patients treated by high-volume (>60 Medicare procedures) physicians (2.25% vs 1.55%; P<.001), but there was no difference in 30-day mortality rates (3.25% vs 3.39%; P =.27). Patients treated at low-volume (<80 Medicare procedures) centers had an increased risk of 30-day mortality vs patients treated at high-volume (>160 Medicare procedures) centers (4.29% vs 3.15%; P<. 001), but there was no difference in the risk of CABG (1.83% vs 1. 83%; P =.96). In patients who received coronary stents, the CABG rate was 1.20% vs 2.78% for patients not receiving stents, and the 30-day mortality rate was 2.83% vs 3.94%. Among patients who received stents, those treated at low-volume centers had an increased risk of 30-day mortality vs those treated at high-volume centers, whereas those treated by low-volume physicians had an increased risk of CABG vs those treated by high-volume physicians. In the era of coronary stents, Medicare patients treated by high-volume physicians and at high-volume centers experience better outcomes following PCIs.

Diagnostic testing following fecal occult blood screening in the elderly.

Screening with a fecal occult blood test (FOBT) has been shown to reduce colorectal cancer mortality in controlled trials. Recently, Medicare approved payment for FOBT screening. We evaluated the pattern of diagnostic testing following the initial FOBT in elderly Medicare beneficiaries. Such follow-up testing would in the long run influence both the cost and the benefit of widespread use of FOBT. Using Medicare's National Claims History System, we identified 24 246 Americans 65 years old or older who received FOBT at physician visits between January 1 and April 30, 1995. Prior to FOBT, these people had no evidence of any conditions for which FOBT might be used diagnostically. We examined relevant diagnostic testing in this cohort during the subsequent 8 months and determined what proportion of those received an evaluation recommended by the American College of Physicians. For every 1000 Medicare beneficiaries who received FOBT, 93 (95% confidence interval = 89-96 per 1000) had positive findings and relevant testing in the subsequent 8 months. Of these, 34% had the recommended evaluation of either colonoscopy or flexible sigmoidoscopy with an air-contrast barium enema. Another 34% received a partial colonic evaluation with either flexible sigmoidoscopy or a barium enema. The remaining 32% received other gastrointestinal (GI) testing without evaluation of the colonic lumen: computed tomography or magnetic resonance imaging of the abdomen (15%), upper GI series (10%), carcinoembryonic antigen (7%), and upper endoscopy (2%). Restricting the analysis to testing performed within 2 months of the initial FOBT yielded similar results. Following FOBT, many Medicare beneficiaries get further diagnostic testing, but only a small proportion receives the recommended evaluation. With this pattern of practice, population screening is likely to be more costly and less effective than estimated from controlled trials.

Diagnostic Testing Following Screening Mammography in the Elderly

To provide some sense of the general frequency and timing of diagnostic testing following screening mammography in the United States, we investigated the experience of women screened in the Medicare population. By use of Medicare's National Claims History System, we identified a cohort (n=23172) of women 65 years old or older screened during the period from January 1, 1995, through April 30, 1995, and tracked each woman over the subsequent 8 months for the performance of additional breast imaging and biopsy procedures. Using two claims-based definitions for newly detected breast cancer, we also estimated the positive predictive value of screening mammography. For every 1000 women aged 65-69 years who underwent screening, 85 (95% confidence interval [CI]=79-91) had follow-up testing in the subsequent 8 months; 76 (95% CI=71-82) had additional breast imaging, and 23 (95% CI=20-26) had biopsy procedures. Corresponding numbers for women aged 70 years or more were similar. Some women underwent repeated examinations; 13% of those receiving diagnostic mammograms had more than one; 11% of those undergoing biopsy procedures had more than one. About half of the women who underwent a biopsy had the procedure more than 3 weeks after the imaging test upon which the decision to perform a biopsy was presumably made. The estimated positive predictive value of an abnormal screening mammogram (defined as a mammogram that engendered additional testing) was 0.08 (95% CI=0.06-0.10) for women aged 65-69 years and 0.14 (95% CI=0.12-0.16) for women aged 70 years or more. Additional testing is a frequent consequence of screening mammography and may require a considerable period of time to come to closure. The need for additional testing, however, is weakly predictive of cancer.

Diagnosis and Treatment of Helicobacter pylori Infection Among California Medicare Patients

Antibiotic treatment of Helicobacter pylori infection in active peptic ulcer disease has been demonstrated to speed ulcer healing, reduce the risk of rebleeding, and prevent long-term recurrence. The objective of this study was to determine whether Medicare patients with peptic ulcer disease who are admitted to acute care hospitals are being tested or treated for H pylori infection as recommended by a National Institutes of Health consensus panel. The study was designed as a retrospective medical records survey. From the Medicare National Claims History File, all persons 65 years and older admitted to California fee-for-service hospitals for peptic ulcer disease in 1994 were identified. A random sample of 600 claims was selected for review. After exclusions, 524 patients were eligible for study. The main outcome measures were (1) the proportion of patients who were tested for H pylori infection by 1 of the 5 available methods (histopathologic study, urease assay, microbiologic culture, serum antibody testing, or urea breath test) and (2) the proportion who were treated with antibiotics (amoxicillin, tetracycline, clarithromycin, or metronidazole) for H pylori infection. Thirty-nine percent of patients with peptic ulcer disease were tested for H pylori infection and 3% were treated empirically. Only 47% of the patients who had a positive diagnostic test result for H pylori were treated with antibiotics. Because diagnosis and treatment of H pylori infection has been demonstrated to improve outcomes and decrease expenses, the data indicate a substantial opportunity to improve the care of elderly Medicare patients with peptic ulcer disease.

Exploring the Relationship Between Inpatient Facility and Physician Services

Medicare hospitalizations involve both facility and physician services. Although several studies analyze hospital-level variations in Medicare inpatient facility and inpatient physician services per admission, few studies directly explore the relationship between these services. Theoretically, inpatient facility and physician services may be complements or substitutes. That is, an increase in facility services may lead to an increase or decrease in physician services and vice versa. This article contributes to the existing literature by exploring directly the relationship between facility and physician services. Medicare physician claims were linked to inpatient hospital stays using data from the Medicare hospital cost reports, the Medicare Patient Analysis and Review file, and the Medicare National Claims History System. In multivariate regression analyses, the (partial) correlations between facility and physician services were positive, which is consistent with complementarity. Standardized regression coefficients indicate that physician services are the single most important determinant of facility services; however, facility services are a less important determinant of physician services. A 10% increase in physician services is associated with at least a 3.0% increase in facility services. Proposals that reduce inpatient physician expenditures also would reduce facility expenditures in the long-run.

The use of Medicare home health care services.

Medicare's home health care program, consisting primarily of home visits by nurses and health aides, was conceived as a means to facilitate hospital discharge. Because home health care is now one of the fastest-growing categories of Medicare expenditures, we analyzed Medicare claims data to determine current patterns of use. We used 1993 data from Medicare's National Claims History File to examine the temporal relation between home visits and hospital discharge, as well as the number of months Medicare enrollees received home health care. To determine whether home visits replaced hospital services, we calculated population-based utilization rates, adjusted for age and sex, for enrollees living in the 310 U.S. metropolitan statistical areas and determined whether the areas with higher rates of home health care also had lower admission rates or shorter lengths of stay. Finally, we compared the geographic variation in use of home health care with that of other Medicare services. Roughly 3 million Medicare enrollees received over 160 million home health care visits in 1993. Seventy-eight percent of the visits either occurred more than a month after hospital discharge (35 percent) or were not associated with any inpatient care during the previous six months (43%). Home health care often represented a long-term intervention: 61 percent of the visits were to enrollees who received home health care for six months or more. We could find no evidence that home health care was substituted for hospital care; the metropolitan statistical areas with higher rates of home health care did not have fewer hospital admissions or shorter lengths of stay. There was more geographic variation in the use of home health care than in the use of other major categories of Medicare services (e.g., hospital admissions and physicians' services). Five states (all in the South) had more than 9000 visits per 1000 enrollees, and 14 states had fewer than 3000 visits per 1000 enrollees. Home health care visits are used primarily to provide long-term care. There is no evidence that services provided at home replace hospital services, and the dramatic geographic variation in home visits suggests a lack of consensus about their appropriate use.

The impact of practicing in multiple hospitals on physician profiles.

Although physicians are all too familiar with the psychologic impact of having multiple responsibilities, the associated impact on practice styles has not been examined systematically. To provide some data on the effects of "work dispersion," we examined the hypothesis that the inpatient resource use of physicians would rise with the number of hospitals in which they work. Data for 1991 from Medicare's National Claims History File were used to profile a sample of attending physicians (n = 33,756) in seven states. The attending physician "profile" was the case mix-adjusted relative value of all physician services (regardless of who delivered them) that were delivered during each patient's hospital stay. Relative value was measured in relative value units, used by Medicare in determining physician payments. The authors then categorized physicians in terms of the number of hospitals to which they admitted patients. Physician profiles were adjusted further to control for geography, physician specialty, and characteristics of the physician's primary (ie, most used) hospital. One third of the physicians in the sample had admissions to more than one hospital. Physicians working in one hospital had inpatient practice profiles 2.1% below the sample mean. Additional hospital affiliations were associated with progressively higher profiles: two hospitals, 2.3% above the mean; three hospitals, 4.5% above; four hospitals, 8.2% above; and five or more hospitals, 11.5% above (all P < 0.01). The practice of medicine in more than one hospital is associated with higher inpatient profiles and shows a dose-response relationship. Physicians and policy makers will need to consider carefully whether there are any associated benefits to justify the increased cost.

Physician Profiling -- An Analysis of Inpatient Practice Patterns in Florida and Oregon

Physician profiling is a method of cost control that focuses on patterns of care instead of on specific clinical decisions. It is one cost-control method that takes into account physicians' desire to curb the intrusion of administrative mechanisms into the clinical encounter. To provide a concrete example of profiling, we analyzed the inpatient practice patterns of physicians in Florida and Oregon. Data for 1991 from Medicare's National Claims History File were used to profile 12,720 attending physicians in Florida and 2589 in Oregon. For each attending physician, we determined the total relative value of all physicians' services delivered during each patient's hospital stay. Relative value was measured in relative-value units (RVUs), according to the resource-based relative-value scale used by Medicare in determining payments to physicians. The mean number of RVUs per admission was then adjusted for the physician's case mix according to the patients' assigned diagnosis-related groups. The influence of the physician's specialty and of selected types of services (such as imaging and endoscopy) was also examined. Florida physicians used markedly more resources, on average, than their colleagues in Oregon (46 vs. 30 case-mix-adjusted RVUs per admission). The difference was apparent for all specialties and all types of service. To illustrate the profiling data potentially available to the medical staffs of individual hospitals, we examined specific data on individual attending physicians and for various types of service for three hospitals' staffs. Despite similar overall profiles that fell below the national mean, each staff had a different practice pattern and would require different efforts to improve efficiency. In an effort to encourage further debate, we have described one method of physician profiling. Profiling data help identify and characterize differences in practice style to which individual physicians or hospital staffs can respond. Because profiling is not based on rigid rules, it is a cost-containment strategy that can easily accommodate legitimate exceptions; it is therefore preferable to methods in which the appropriateness of each clinical decision is judged separately.