Large-scale biomonitoring of bisphenol analogues and their metabolites in human urine from Guangzhou, China: Implications for health risk assessment.

Bisphenol analogues (BPs) are ubiquitous in the environment and have gained significant attention regarding their associated health risks. However, there is a lack of comprehensive biomonitoring data on BPs and their metabolites in human urine. To address this, we conducted a study evaluate the exposure to BPs in the general population of Guangzhou, China. A total of 1440 urine samples were collected from volunteers and analyzed for the presence of BPs and their metabolites after being pooled into 36 groups based on age and gender. The findings revealed the common detection of ten free-form BPs, as well as the urinary metabolites of BPA and BPS, in the pooled urine samples. BPA was the predominant free-form compound, constituting 50% of the total BPs. The primary urinary metabolites of BPA and BPS are BPA-G and BPS-G, respectively, indicating glucuronidation as their primary metabolic pathway. The composition of urinary metabolites of BPA and BPS varied by age and sex, while the concentration of total BPs in urine was not significantly associated with age and sex. Enzymatic hydrolysis yielded a mean amplification of individual BPs concentrations in urine samples ranging from 1.8 times (BPA) to 4.6 times (BPS). Based on the outcomes, it was estimated that conjugated forms accounted for 96.9%, 96.2%, 94.7%, 94.1%, 92.6%, 89.1%, 87.3%, 87.2%, 87.1% and 85.8% of BPP, BPAF, BPZ, BPE, BPAP, BPF, BPA, BPC, BPS and BPF, respectively, in the pooled urine samples. Preliminary risk assessments indicated that the estimated daily intake of BPA was much higher than the latest proposed tolerable daily intake. Due to the unavailability of health-based guideline values for alternative BPs, some of them exhibit daily intakes comparable to BPA, implying that greater attention should be paid to health risks associated with exposure to BPs.

Rapid imaging and product screening with low-cost line-field Fourier domain optical coherence tomography.

Fourier domain optical coherence tomography (FD-OCT) is a well-established imaging technique that provides high-resolution internal structure images of an object at a fast speed. Modern FD-OCT systems typically operate at speeds of 40,000-100,000 A-scans/s, but are priced at least tens of thousands of pounds. In this study, we demonstrate a line-field FD-OCT (LF-FD-OCT) system that achieves an OCT imaging speed of 100,000 A-scan/s at a hardware cost of thousands of pounds. We demonstrate the potential of LF-FD-OCT for biomedical and industrial imaging applications such as corneas, 3D printed electronics, and printed circuit boards.

Assessment of BPA and BPS exposure in the general population in Guangzhou, China - Estimation of daily intakes based on urinary metabolites.

Human exposure to bisphenol A (BPA) and bisphenol S (BPS) has garnered considerable global health concerns. In this paper, the daily intake (DI) of BPA and BPS in the general population of Guangzhou, China, were back-calculated using the biomarkers BPA glucuronides (BPA-G) and BPS glucuronides (BPS-G), respectively. The biomarkers are preferable to total BPA and BPS measurements because they are not susceptible to external contamination. A total of 1440 urine samples were gathered from the general population in Guangzhou, China, which were classified by age and sex into 36 pooled urine samples. 100% and 98% of pooled urine samples contained BPA-G and BPS-G at median values of 1.57 and 0.38 ng/mL, respectively. Based on urinary BPA-G and BPS-G concentrations, we determined the median DI of BPA and BPS to be 31.07 and 7.37 ng/(kg bw*d), respectively, and the highest values to be 106.77 ng/(kg bw*d) and 18.19 ng/(kg bw*d), respectively. Furthermore, our results showed that for the entire dataset, the DI of BPA and BPS were considerably greater in males than in females (p < 0.01)and declined significantly with age (p < 0.05). For risk assessment, the estimated DIs of BPA and BPS were much lower than the European Food Safety Authority' s (EFSA) the temporary acceptable reference dose of 4 µg/(kg bw*d) advised for BPA, suggesting that the exposure risk of BPA and BPS for Guangzhou population is within a controllable safety range. This is the first study to investigate BPA and BPS exposure in the general population of Guangzhou, China, on the basis of urinary metabolites.

Luteolin cooperated with metformin hydrochloride alleviates lipid metabolism disorders and optimizes intestinal flora compositions of high-fat diet mice.

Luteolin (LU) is a flavonoid compound and metformin hydrochloride (MH) is a kind of drug. Studies have shown that both LU and MH have the function of hypoglycemic effect. However, there are few reports indicating that LU cooperated with MH (LU·MH) can relieve lipid metabolism disorders and optimize intestinal flora compositions of high-fat diet mice. In this research, we investigated the effects of LU, MH and LU·MH on lipid metabolism disorders and intestinal flora composition in high-fat diet mice. The study found that compared with high-fat diet (HFD) alone, LU, MH and LU·MH could significantly reduce the lipid metabolism disorder. Furthermore, compared with LU or MH alone, the biochemical indicators of LU·MH were significantly improved and the results of the histopathological section also showed that LU·MH has stronger liver repair ability. It revealed that the potential mechanisms of the LU·MH alleviating lipid metabolism disorders were involved in the simultaneous regulation of SREBP-1c/FAS and SREBP-1c/ACC/Cpt-1. In addition, LU·MH could regulate the intestinal flora compositions. This includes significantly reducing the ratio of Firmicutes and Bacteroidetes(F/B) and at the family level, increasing the relative abundance of Lachnospiraceae, Helicobacteraceae, Marinifilaceae and Peptococcaceae to relieve lipid metabolism disorders. In conclusion, the work found that LU·MH regulates the signal pathway of SREBP-1c/FAS and SREBP-1c/ACC/Cpt-1 simultaneously and decreases the ratio of F/B, as well as increases the relative abundance of certain microbiota to alleviate the lipid metabolism disorders of HFD-fed mice.

Angiotensin II for the treatment of distributive shock in the intensive care unit: A US cost-effectiveness analysis.

BACKGROUND: Patients with distributive shock who are unresponsive to traditional vasopressors are commonly considered to have severe distributive shock and are at high mortality risk. Here, we assess the cost-effectiveness of adding angiotensin II to the standard of care (SOC) for severe distributive shock in the US critical care setting from a US payer perspective. METHODS: Short-term mortality outcomes were based on 28-day survival rates from the ATHOS-3 study. Long-term outcomes were extrapolated to lifetime survival using individually estimated life expectancies for survivors. Resource use and adverse event costs were drawn from the published literature. Health outcomes evaluated were lives saved, life-years gained, and quality-adjusted life-years (QALYs) gained using utility estimates for the US adult population weighted for sepsis mortality. Deterministic and probabilistic sensitivity analyses assessed uncertainty around results. We analyzed patients with severe distributive shock from the ATHOS-3 clinical trial. RESULTS: The addition of angiotensin II to the SOC saved .08 lives at Day 28 compared to SOC alone. The cost per life saved was estimated to be $108,884. The addition of angiotensin II to the SOC was projected to result in a gain of .96 life-years and .66 QALYs. This resulted in an incremental cost-effectiveness ratio of $12,843 per QALY. The probability of angiotensin II being cost-effective at a threshold of $50,000 per QALY was 86 percent. CONCLUSIONS: For treatment of severe distributive shock, angiotensin II is cost-effective at acceptable thresholds.

Cost-Effective Edge Server Placement in Wireless Metropolitan Area Networks.

Remote clouds are gradually unable to achieve ultra-low latency to meet the requirements of mobile users because of the intolerable long distance between remote clouds and mobile users and the network congestion caused by the tremendous number of users. Mobile edge computing, a new paradigm, has been proposed to mitigate aforementioned effects. Existing studies mostly assume the edge servers have been deployed properly and they just pay attention to how to minimize the delay between edge servers and mobile users. In this paper, considering the practical environment, we investigate how to deploy edge servers effectively and economically in wireless metropolitan area networks. Thus, we address the problem of minimizing the number of edge servers while ensuring some QoS requirements. Aiming at more consistence with a generalized condition, we extend the definition of the dominating set, and transform the addressed problem into the minimum dominating set problem in graph theory. In addition, two conditions are considered for the capacities of edge servers: one is that the capacities of edge servers can be configured on demand, and the other is that all the edge servers have the same capacities. For the on-demand condition, a greedy based algorithm is proposed to find the solution, and the key idea is to iteratively choose nodes that can connect as many other nodes as possible under the delay, degree and cluster size constraints. Furthermore, a simulated annealing based approach is given for global optimization. For the second condition, a greedy based algorithm is also proposed to satisfy the capacity constraint of edge servers and minimize the number of edge servers simultaneously. The simulation results show that the proposed algorithms are feasible.

Alignment-free Transcriptomic and Metatranscriptomic Comparison Using Sequencing Signatures with Variable Length Markov Chains.

The comparison between microbial sequencing data is critical to understand the dynamics of microbial communities. The alignment-based tools analyzing metagenomic datasets require reference sequences and read alignments. The available alignment-free dissimilarity approaches model the background sequences with Fixed Order Markov Chain (FOMC) yielding promising results for the comparison of microbial communities. However, in FOMC, the number of parameters grows exponentially with the increase of the order of Markov Chain (MC). Under a fixed high order of MC, the parameters might not be accurately estimated owing to the limitation of sequencing depth. In our study, we investigate an alternative to FOMC to model background sequences with the data-driven Variable Length Markov Chain (VLMC) in metatranscriptomic data. The VLMC originally designed for long sequences was extended to apply to high-throughput sequencing reads and the strategies to estimate the corresponding parameters were developed. The flexible number of parameters in VLMC avoids estimating the vast number of parameters of high-order MC under limited sequencing depth. Different from the manual selection in FOMC, VLMC determines the MC order adaptively. Several beta diversity measures based on VLMC were applied to compare the bacterial RNA-Seq and metatranscriptomic datasets. Experiments show that VLMC outperforms FOMC to model the background sequences in transcriptomic and metatranscriptomic samples. A software pipeline is available at https://d2vlmc.codeplex.com.

Survey and Chart Review to Estimate Medicare Cost Savings for Home Health as an Alternative to Hospital Admission Following Emergency Department Treatment.

BACKGROUND: Almost 70% of hospital admissions for Medicare beneficiaries originate in the emergency department (ED). Research suggests that some of these patients' needs may be better met through home-based care options after evaluation and treatment in the ED. OBJECTIVE: We sought to estimate Medicare cost savings resulting from using the Home Health benefit to provide treatment, when appropriate, as an alternative to inpatient admission from the ED. METHODS: This is a prospective study of patients admitted from the ED. A survey tool was used to query both emergency physicians (EPs) and patient medical record data to identify potential candidates and treatments for home-based care alternatives. Patient preferences were also surveyed. Cost savings were estimated by developing a model of Medicare Home Health to serve as a counterpart to the actual hospital-based care. RESULTS: EPs identified 40% of the admitted patients included in the study as candidates for home-based care. The top three major diagnostic categories included diseases and disorders of the respiratory system, digestive system, and skin. Services included intravenous hydration, intravenous antibiotics, and laboratory testing. The average estimated cost savings between the Medicare inpatient reimbursement and the Home Health counterpart was approximately $4000. Of the candidate patients surveyed, 79% indicated a preference for home-based care after treatment in the ED. CONCLUSIONS: Some Medicare beneficiaries could be referred to Home Health from the ED with a concomitant reduction in Medicare expenditures. Additional studies are needed to compare outcomes, develop the logistical pathways, and analyze infrastructure costs and incentives to enable Medicare Home Health options from the ED.

PyroHMMvar: a sensitive and accurate method to call short indels and SNPs for Ion Torrent and 454 data.

MOTIVATION: The identification of short insertions and deletions (indels) and single nucleotide polymorphisms (SNPs) from Ion Torrent and 454 reads is a challenging problem, essentially because these techniques are prone to sequence erroneously at homopolymers and can, therefore, raise indels in reads. Most of the existing mapping programs do not model homopolymer errors when aligning reads against the reference. The resulting alignments will then contain various kinds of mismatches and indels that confound the accurate determination of variant loci and alleles. RESULTS: To address these challenges, we realign reads against the reference using our previously proposed hidden Markov model that models homopolymer errors and then merges these pairwise alignments into a weighted alignment graph. Based on our weighted alignment graph and hidden Markov model, we develop a method called PyroHMMvar, which can simultaneously detect short indels and SNPs, as demonstrated in human resequencing data. Specifically, by applying our methods to simulated diploid datasets, we demonstrate that PyroHMMvar produces more accurate results than state-of-the-art methods, such as Samtools and GATK, and is less sensitive to mapping parameter settings than the other methods. We also apply PyroHMMvar to analyze one human whole genome resequencing dataset, and the results confirm that PyroHMMvar predicts SNPs and indels accurately. AVAILABILITY AND IMPLEMENTATION: Source code freely available at the following URL: https://code.google.com/p/pyrohmmvar/, implemented in C++ and supported on Linux. .

Effects of coverage gap reform on adherence to diabetes medications.

OBJECTIVES: To investigate the impact of Part D coverage gap reform on diabetes medication adherence. STUDY DESIGN: Retrospective data analysis based on pharmacy claims data from a national pharmacy benefit manager. METHODS: We used a difference-in-difference-indifference method to evaluate the impact of coverage gap reform on adherence to diabetes medications. Two cohorts (2010 and 2011) were constructed to represent the last year before Affordable Care Act (ACA) reform and the first year after reform, respectively. Each patient had 2 observations: 1 before and 1 after entering the coverage gap. Patients in each cohort were divided into groups based on type of gap coverage: no coverage, partial coverage (generics only), and full coverage. RESULTS: Following ACA reform, patients with no gap coverage and patients with partial gap coverage experienced substantial drops in copayments in the coverage gap in 2011. Their adherence to diabetes medications in the gap, measured by percentage of days covered, improved correspondingly (2.99 percentage points, 95% confidence interval [CI] 0.49-5.48, P = .019 for patients with no coverage; 6.46 percentage points, 95% CI 3.34-9.58, P <.0001 for patients with partial coverage). Patients with full coverage also had lower copayments in the gap in 2011. However, their adherence did not increase (-0.13 percentage point, P = .8011). CONCLUSIONS: In the first year of ACA coverage gap reform, copayments in the gap decreased substantially for all patients. Patients with no coverage and patients with partial coverage in the gap had better adherence in the gap in 2011.

PyroHMMsnp: an SNP caller for Ion Torrent and 454 sequencing data.

Both 454 and Ion Torrent sequencers are capable of producing large amounts of long high-quality sequencing reads. However, as both methods sequence homopolymers in one cycle, they both suffer from homopolymer uncertainty and incorporation asynchronization. In mapping, such sequencing errors could shift alignments around homopolymers and thus induce incorrect mismatches, which have become a critical barrier against the accurate detection of single nucleotide polymorphisms (SNPs). In this article, we propose a hidden Markov model (HMM) to statistically and explicitly formulate homopolymer sequencing errors by the overcall, undercall, insertion and deletion. We use a hierarchical model to describe the sequencing and base-calling processes, and we estimate parameters of the HMM from resequencing data by an expectation-maximization algorithm. Based on the HMM, we develop a realignment-based SNP-calling program, termed PyroHMMsnp, which realigns read sequences around homopolymers according to the error model and then infers the underlying genotype by using a Bayesian approach. Simulation experiments show that the performance of PyroHMMsnp is exceptional across various sequencing coverages in terms of sensitivity, specificity and F1 measure, compared with other tools. Analysis of the human resequencing data shows that PyroHMMsnp predicts 12.9% more SNPs than Samtools while achieving a higher specificity. (http://code.google.com/p/pyrohmmsnp/).

Failure to intensify hypertension therapy after rejected aliskiren claims.

BACKGROUND: Failure to intensify therapy when indicated is a serious problem in the management of hypertension. Patients having an antihypertensive prescription rejected because of utilization management tools may be at a high risk of failing to intensify their therapy when it is warranted. OBJECTIVE: The goal of this study was to investigate the patterns of therapy change after rejected aliskiren claims because of utilization management tools such as prior authorization, step therapy, and restrictive formulary. METHODS: A retrospective study was conducted using data from a large national pharmacy benefits manager. Patients with a rejected aliskiren claim because of utilization management and who were naive to aliskiren treatment before having a rejected aliskiren claim were included. Patients were followed up for 6 months after the initial rejected aliskiren claim to see whether there was a therapy change. Therapy change was defined as titration of old regimens, fulfillment of aliskiren, or fulfillment of a new antihypertensive medication not used previously. RESULTS: A total of 1955 patients were identified (mean age, 64.5 years; 54.4% female). Six months after having rejected aliskiren claims, 36.8% overcame the utilization management and filled aliskiren; 45.1% filled a new antihypertensive medication not used previously; and 10.8% patients titrated old antihypertensive medications. More than one quarter of patients (28.4%) had no change in their antihypertensive treatment. Logistic regression analysis revealed that patients rejected because of prior authorization (odds ratio = 4.00 [95% CI, 1.89-8.44]) or step therapy (odds ratio = 2.59 [95% CI, 1.26-5.32]) were more likely to have a therapy change compared with patients rejected because of a restrictive formulary. CONCLUSIONS: A significant number of patients had no therapy change 6 months after having rejected aliskiren claims because of utilization management tools, indicating potential clinical inertia or lack of therapy intensification in hypertension management. Patients with restrictive formularies were least likely to have a therapy change. More aggressive follow-up with patients with a rejected claim may be warranted to reduce treatment gaps.

Characteristics and assessment of phthalate esters in urban dusts in Guangzhou city, China.

Phthalate esters (PAEs) were examined in indoor and outdoor dust samples from the subtropical city of Guangzhou, China. The ∑(16)PAEs concentrations ranged from 121 to 3,223 µg g(-1) dust, with the median concentration of 840 µg g(-1) dust. Significantly higher concentrations of PAEs in dust samples were found in offices where electrical and electronic devices, carpet pads, and office furniture were widely used. Of the 16 PAEs, diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs in indoor and outdoor dust samples, and accounted for >96.8% and >93.1% of the ∑(16)PAEs concentrations, respectively. The median daily inhalation exposure of ∑(16)PAEs were 3.53 and 0.247 µg kg(-1) body weight day(-1), and at the 95(th) percentile were 7.62 and 0.530 µg kg(-1) body weight day(-1), up on the measured concentrations and estimated dust ingestion rates, respectively, for toddles and adults. The ubiquitous distribution of PAEs as noted in this study suggests the need for detailed assessment of PAEs concentrations using more sites and to further investigate the factors influencing PAEs exposure in China.

Effects of copayment on initiation of smoking cessation pharmacotherapy: an analysis of varenicline reversed claims.

BACKGROUND: Smoking cessation pharmacotherapy is a critical component of smoking cessation treatment, but most smokers use neither pharmacotherapy nor behavior counseling in attempts to quit smoking. The low rate of smoking cessation medication use is of great concern because it can negatively influence the odds of success in smoking cessation. OBJECTIVE: This study was conducted to analyze how copayment may influence the likelihood of initiating smoking cessation pharmacotherapy following a reversed varenicline claim. METHODS: A retrospective cohort analysis was performed using pharmacy claims data from a large national pharmacy benefits management company. Reversed claims were claims first approved by the health plan and then reversed by the pharmacy. The study population included patients with over-the-counter nicotine replacement therapy coverage and a reversed varenicline claim between January 2007 and April 2008 and who were naive to varenicline before the reversed claim. A multivariate logistic regression analysis was conducted to evaluate the probability of initiating any smoking cessation pharmacotherapy (varenicline, bupropion, and prescribed or over-the-counter nicotine replacement therapy) within 183 days of the reversed claim. RESULTS: A total of 20,451 patients met the inclusion criteria. The mean (SD) age of patients was 47.8 (12.4) years, with 57.41% being female. The majority (87.72%) were covered in commercial managed care plans. A total of 17,028 patients (83.26%) had at least 1 smoking cessation medication filled 6 months after their reversed claim. The odds ratios for patients who had any smoking cessation medication filled and copayments of $31 to $40, $41 to $60, or >$60 were 0.68, 0.48, and 0.35, respectively (all, P < 0.001), compared with patients with copayments of $0 to $5. CONCLUSIONS: The findings suggest that some patients might have been deterred by a high copayment (≥$31) and, ultimately, did not fill any smoking cessation treatments within 183 days of reversed varenicline claims. It is important to address this potential treatment gap to improve the effectiveness of smoking cessation therapy.

Utilization management for smoking cessation pharmacotherapy: varenicline rejected claims analysis.

OBJECTIVE: To evaluate the impact of utilization management methods on use of smoking cessation medication. STUDY DESIGN: Retrospective cohort analysis of pharmacy claims data. METHODS: The study population included patients at least 18 years of age, naive to varenicline, and with a rejected varenicline claim between January 2007 and April 2008 because of 1 of 4 utilization management restrictions: drug not covered, prior authorization, step therapy, or quantity limits. The outcome variable was whether patients used any smoking cessation medication including varenicline, bupropion, and nicotine replacement therapy (prescribed and over-the-counter) within 6 months of the rejected varenicline claim. Multivariable logistic regression was conducted to evaluate the probability of filling a prescription for any smoking cessation medication. RESULTS: A total of 15,597 patients were identified. Within 6 months after the rejected claims, 8393 (53.8%) patients filled at least 1 smoking cessation medication, 7864 (93.7%) of whom filled varenicline. Compared with quantity limits, the odds ratios for filling any smoking cessation medication after the rejected varenicline claim were 0.01 (95% confidence interval [CI], 0.01-0.02) for varenicline not covered, 0.07 (95% CI, 0.06-0.09) for step therapy, and 0.18 (95% CI, 0.16-0.20) for prior authorization. Higher out-of-pocket expense was associated with a lower probability of filling any smoking cessation medication. CONCLUSION: About half of the patients in this study did not fill any smoking cessation medication following a rejected varenicline claim. It is important to address this treatment gap in support of patients seeking smoking cessation therapy.

The impact of value-based benefit design on adherence to diabetes medications: a propensity score-weighted difference in difference evaluation.

OBJECTIVE: To evaluate the impact of value-based benefit design (VBBD) on adherence to diabetes medications. METHODS: Health Alliance Medical Plans piloted VBBD for diabetes medications for a subgroup of 5400 enrollees in January 2007 while keeping drug benefits unchanged for the remaining plan enrollees. A difference in difference method (DID) was used to evaluate the effect of VBBD based on pharmacy claim data. Patients with unchanged benefits in the same plan were used as the control group. Adherence was measured by the proportion of days covered. Propensity score weighting was used to balance characteristics of the case group and the control group. RESULTS: There were 71 patients in the case group and 5037 patients in the control group. The patients in the two groups had comparable characteristics after propensity score weighting. After the implementation of VBBD, the average copayment per 30 days of supply for diabetes medications decreased from $15.3 to $10.1 for the case group and increased from $14.6 to $15.1 for the control group. The probability of being adherent increased from 75.3% to 82.6% for the case group and was roughly unchanged from 79.1% to 78.5% for the control group. Propensity score-weighted DID analysis showed that patients with copayment reduction had greater odds of being adherent: odds ratio=1.56, P=0.03, 95% confidence interval 1.04-2.34. CONCLUSION: A VBBD program that reduced the copayment for diabetes medications by 36.1% reduced the number of nonadherent patients by 30.0%.

Part D coverage gap and adherence to diabetes medications.

OBJECTIVE: To evaluate the impact of Medicare Part D coverage gap (donut hole) on adherence to diabetes medications. STUDY DESIGN: Retrospective cohort analysis based on pharmacy claims data. METHODS: The sample included 12,881 Medicare Part D beneficiaries with diabetes who entered the coverage gap in 2008. Sample patients had 3 different levels of coverage in the donut hole: no coverage, generic drug coverage only, and both generic and brand-name drug coverage. Adherence was measured by the proportion of days covered. We used a difference-in-difference model to evaluate the effect of coverage gap on adherence. RESULTS: In the donut hole, the average copayment for diabetes medications increased substantially for beneficiaries with no coverage and beneficiaries with generic drug coverage only, whereas the average copayment for beneficiaries with both generic and brand-name medication coverage declined slightly. Compared with beneficiaries with full coverage of both generic and brand-name drugs, beneficiaries with no coverage (odds ratio[OR] = 0.617, P <.0001, 95% confidence interval [CI] = 0.523, 0.728) and beneficiaries with generic drug coverage only (OR = 0.702, P <.0001, 95% CI = 0.604, 0.816) were significantly less likely to be adherent after entering the donut hole. The difference between having generic coverage and no coverage was not significant (P = .1586). CONCLUSIONS: The coverage gap in the Medicare Part D program has a significant negative impact on medication adherence among beneficiaries with diabetes. Availability of brand-name drug coverage in the donut hole is critical to adherence to diabetes medications.

The effect of medicare health maintenance organizations on hospitalization rates for ambulatory care-sensitive conditions.

OBJECTIVE: The objective of this study was to estimate the effect of Medicare Health Maintenance Organization (HMO) enrollment on hospitalization rates and total inpatient days for ambulatory care-sensitive conditions (ACSCs) after controlling for selection. RESEARCH DESIGN: Simultaneous equations using a discrete factor selection model are used to estimate the probability of HMO enrollment, hospitalization rates, and total inpatient days for ACSCs. SUBJECTS: Enrollment data on Medicare beneficiaries in California were linked to hospital discharge data from the California Office of Statewide Health Planning and Development for January through December 1996. The following beneficiaries were excluded: 1) end-stage renal disease, 2) under 65 years of age, 3) not covered by both Medicare Part A and Part B, 4) switched between HMOs and fee-for-service (FFS), and 5) switched between HMOs. The sample was stratified by age, gender, race, county, disability, Medicaid eligibility, HMO status, and death. A 2% random sample from the 4 California counties with the largest Medicare enrollment yielded 10,448 HMO enrollees and 11,803 FFS beneficiaries. RESULTS: Using a discrete factor selection model, we estimated the rate of ACSC hospitalizations among FFS beneficiaries would decline from 51.2 to 44.2 per 1000 if all FFS beneficiaries joined an HMO. Similarly, the mean total inpatient days for ACSC hospitalizations would be reduced from 7.5 days to 5.1 days if all FFS beneficiaries joined an HMO. CONCLUSIONS: After controlling for selection, Medicare HMO enrollees have lower hospitalization rates and fewer total inpatient days for 15 ACSCs than Medicare FFS beneficiaries. These findings suggest selection of healthier beneficiaries into HMOs does not completely explain their lower rates of ACSC hospitalization.