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Biomedical subjects

M Shwartz

Publications and source records attributed to M Shwartz.

At least 55 records · Page 3Linked to original sources
PubMed1986

The expected benefits from alternative frequencies of bitewing radiograms.

From an analysis of serial bitewing radiograms, we have developed a mathematical model of the initiation and progression of approximal carious lesions in the permanent teeth. The model is used to estimate the expected number of lesions, per individual, not detected until they reach the inner half of the dentin, as a function of the frequency with which radiograms are taken between the ages of 8 and 20 years. If radiograms are performed every 6 months and lesions not restored until radiolucencies appear in the dentin, under 5% of all lesions developing over the 12-year period will reach the inner half of the dentin before detection. If radiograms are taken every 2 years, about 18% of all lesions will have reached the inner half of the dentin before detection. The sensitivity of these conclusions to different assumptions is examined.

Adolescent↗
PubMed1985

Case-mix and cost differences between teaching and nonteaching hospitals.

The case loads of 11 teaching and 20 nonteaching hospitals are compared, using the original 383 diagnosis-related groups (DRGs) to analyze the extent to which case-mix differences contribute to differences in average cost per case. Case-mix differences are concentrated in a small proportion of DRGs. Teaching hospitals have relatively more surgery cases and neoplasms, and nonteaching hospitals have more cases with heart conditions and infectious diseases. Most nonteaching hospitals have a similar case mix, but among the teaching hospitals, there are two distinct case-mix types, one with which only teaching hospitals are correlated, one that correlates with both teaching and nonteaching hospitals. The average cost per case is more than 60% more expensive in teaching hospitals. Only approximately one quarter of this higher cost is accounted for by case-mix differences. The rest results from the fact that patients in the same DRGs cost more, on average, in teaching than in nonteaching hospitals.

Adult↗
PubMed1984

Case mix in end-stage renal disease. Differences between patients in hospital-based and free-standing treatment facilities.

This study examines the mix of cases in facilities for the treatment of end-stage renal disease in Michigan during the period January 1973 through September 1981. We compared 3135 patients treated in 29 hospital-based facilities with 307 patients treated in five proprietary, free-standing facilities. Patients were assigned to one of five severity groups on the basis of age, race, primary renal diagnosis, and accompanying conditions. The five severity groups were differentiated by the probability of death in the first year of treatment and the risk of death over the course of treatment. We then compared the distribution of patients in the five severity groups in hospital-based facilities with that in free-standing facilities. Hospital-based facilities had a higher percentage of patients in the higher-severity groups. When severity was measured by one-year survival, the difference was statistically significant. Sixty per cent of hospital-based patients were in the three highest severity groups, as compared with 50 per cent of patients in free-standing facilities. Within each severity group, hospital-based patients had a lower five-year survival rate than patients in free-standing facilities. Our findings suggest that the case mix in hospital-based facilities may include more severe cases than that in proprietary, free-standing facilities, but more data from more facilities will be needed before firm conclusions can be drawn. If the cost of providing services is related to case-mix severity, such data could have implications for federal reimbursement policies.

Adolescent↗
PubMed1984

A longitudinal analysis from bite-wing radiographs of the rate of progression of approximal carious lesions through human dental enamel.

Four to ten years of serial bite-wing radiographs from over 700 children from five groups, three in Sweden and two in the U.S., were interpreted. By analysing changes in the depth of unfilled lesions over time, the mean time and probability distribution for the time a lesion remains in both the outer half and inner half of the enamel were estimated. The procedure incorporated information on filled lesions and non-progressing lesions and thus minimized bias that results in overestimation of the progression rate. In primary teeth, in both the U.S. and Swedish groups, it took on average 12 months for a lesion to progress through the outer half of the enamel and on average 10-12 months for a lesion to progress through the inner half. In newly-erupted first permanent molars, it took 21-23 months for a lesion to progress through the outer half of the enamel and between 19 (U.S. data) and 28 months (Swedish data) for progression through the inner half. In older adolescents in the two Swedish groups, progression was slower: 38-41 months through the outer-half and 47-56 months through the inner-half. In older U.S. adolescents, progression appeared to be more rapid: 16 months through the outer half of the enamel and 27 months through the inner half. The duration of time a lesion remains in different halves of the enamel could be approximated by a piecewise exponential or exponential probability distribution, which exhibits extreme variability. Assuming duration in each half of the enamel follows an exponential distribution with a mean of 2 yr, about 10 per cent of new lesions will progress through the enamel in one year and 25 per cent in two years. However, over 40 per cent of the lesions will not have progressed in 4 yr. There were no consistent differences in the rate of progression by sex, between upper and lower dentitions, for premolars versus molars, or between high and low-risk individuals.

Adolescent↗
PubMed1984

DRG-based case mix and public hospitals.

The 12 acute care public hospitals in New York City (HHC hospitals) are compared with a matched group of nonpublic hospitals (non-HHC hospitals). The following questions are considered: using DRGs to define case mix, how does the case mix of HHC and non-HHC hospitals differ; to what extent do differences in case mix account for differences in average length of stay (ALOS); can factors other than case mix be identified that may explain differences in ALOS? Although about one half of the 20 most prevalent DRGs are similar in both types of institutions, there are clear case mix differences. The higher percentage of abortion, psychiatric, and chemical dependence discharges and the lower prevalence of surgery in HHC hospitals contribute to this difference. The case load is more concentrated in fewer DRGs in HHC hospitals. HHC hospitals treat more patients in DRGs with a shorter ALOS, but, on the average, patients in the same DRG stay more than 1 day longer in HHC facilities. To some extent, this longer LOS can be explained by differences in payor type, primary diagnosis within a DRG, and, most important, in the percentage of outlier patients.

Costs and Cost Analysis↗
PubMed1984

Use of the Kaplan-Meier estimate to reduce biases in estimating the rate of caries progression.

An important determinant of how often to perform dental radiography is how rapidly dental caries progress. Estimates of the rate of progression of dental caries have been biased by the elimination of filled lesions and non-progressing lesions (i.e. censored data) from the analysis. We illustrate the use of the Kaplan-Meier estimate to incorporate information from these cases and demonstrate the effect of using this information on estimates of the rate of progression of approximal caries.

Adolescent↗
PubMed1984

Study design to reduce biases in estimating the percentage of carious lesions that do not progress within a time period.

Much of the available information on the rate of caries progression comes from studies in which two examinations have been done and the percentage of lesions that do not progress from a carious state between the examinations recorded. Extrapolation from this type of study is subject to two offsetting biases. On the one hand, slow progressing lesions that have been in a state for a long time before the first examination may progress between examinations. When these are counted as lesions that progress within the time period between the two examinations, there will be an underestimation of non-progressing lesions. On the other hand, slow progressing lesions will be over-represented in the sample of lesions detected at the first examination. This will result in an overestimation of non-progressing lesions. We suggest a three examination protocol to minimize these biases.

Dental Caries↗
PubMed1984

Reliability of coding depth of approximal carious lesions from non-independent interpretation of serial bitewing radiographs.

In order to help understand the effectiveness of preventive care and the source of variation in treatment decisions, it is important to determine intra- and interexaminer agreement on the presence and depth of radiolucencies on bitewing radiographs when serial radiographs on individuals are available for interpretation. Serial radiographs on 24 subjects were read in succession, and one of four depth codes was assigned to approximal lesions. The radiographs were then read a second time, both by the person who had initially read the radiographs and by a second reader. Intraexaminer agreement on presence of a lesion ranged from 60% to 90%; four of the five readers had an agreement of over 78%. Interexaminer agreement on presence of a lesion ranged from 71% to 84%. Intraexaminer agreement on depth of lesion ranged from 64% to 80%; four readers had an agreement of over 73%. Interexaminer agreement on depth of lesion ranged from 59% to 76%.

Adolescent↗
PubMed1984

An analysis of hospital case mix, cost, and payment differences for Medicare, Medicaid, and Blue Cross Plan patients using DRGs.

To increase our understanding of case mix as a major contributor to variability in hospital costs, we examined the relationship among case mix, resource consumption, and payments for all Medicare, Medicaid, and Blue Cross Plan patients discharged from 28 hospitals in New York State. Case mix differences among the three payers were found to contribute to differences in overall average cost per case, although residual differences in costs existed at the DRG level. Medicare and Medicaid payments more often covered the actual costs of their patients than did Blue Cross Plan payments. Our results indicate the importance of payer-specific data in the design of effective and equitable reimbursement and cost containment strategies.

Blue Cross Blue Shield Insurance Plans↗
PubMed1982

Impact of a mandatory second-opinion program on medicaid surgery rates.

The effect of the Massachusetts second-opinion program on the volume of elective surgery in the Medicaid population was assessed using two approaches: a study of the program experience and surgery decisions of 2,501 program referrals, and an analysis of Medicaid surgery rates before and after program implementation. Nonconfirmation rates, which averaged 14.5 per cent, varied by procedure from 4 per cent for cholecystectomy to 26 per cent for disc surgery. The patient's surgery decision was related to the outcome of the second-opinion consultation: 85.5 per cent of the confirmed patients had the originally proposed operation, as compared with 31 per cent of the nonconfirmed patients. In the year after program implementation, the program was associated with a 20 per cent reduction in the volume of those procedures covered by the program. The greatest percentage declines were for hysterectomies, meniscectomies, hemorrhoidectomies and tonsillectomies/adenoidectomies. The decline in surgery rates was attributed both to a direct effect on patients referred to the program and to a sentinel effect whereby fewer operations were proposed. We conclude that the mandatory second-opinion program in Massachusetts saved Medicaid $3 to $4 for every dollar spent.

Costs and Cost Analysis↗
PubMed1981

The effect of a thirty per cent reduction in physician fees on Medicaid surgery rates in Massachusetts.

In this paper, we use an interrupted time series analysis to assess the effect of a 30 per cent reduction in the Medicaid reimbursement fee for physician services on the rate at which eight elective surgical procedures were performed in the Massachusetts Medicaid population. Tonsillectomy/adenoidectomy is the only procedure in which there was a statistically significant decline in the rate of surgery in most areas of the state following the fee cut. There is some evidence of an increase in the rate of disc surgeries/spinal fusions. The rate of other procedures increased in some areas of the state and decreased in other areas in the period after the fee cut.

Adenoidectomy↗
PubMed1981

Validation and use of a mathematical model to estimate the benefits of screening younger women for breast cancer.

A model of breast cancer is validated by showing that predictions from the model are similar to a variety of reported data on breast cancer. In particular, the model reproduces the finding reported from the HIP screening program that there is no statistically significant benefit from screening younger women for breast cancer. Based on the model, it is estimated that yearly screening between age 40 and 70 with a joint modality consisting of a clinical examination and mammography will realize slightly under one-half the gain in life expectancy (from age 40) that would be realized if breast cancer mortality were eliminated. Most of this gain (about 70%) would be realized if only the clinical examination were performed yearly. Up to 90% would be realized if biannual mammograms were added to the yearly clinical examination.

Adult↗
PubMed1980

Estimates of lead time and length bias in a breast cancer screening program.

Assume that the benefit of screening for breast cancer with a combination of mammography and a clinical examination is measured by comparing the five-year survival rate of women detected by screening to the five-year survival rate of women surface clinically with breast cancer, e.g., to the survival rate of women reported in End Results In Cancer. In this paper a mathematical model is used to estimate the percentage of the observed difference in five-year survival rates between women in these two groups that is due to lead time and length bias. For women detected at an initial screen, the best estimate is that about 50% of the observed difference is due to bias and 50% to earlier detection. However, the percent due to bias may be as low as 20% and as high as 72%. These estimates are relatively insensitive to the age of the women screened. For women detected at a second screen given one year later, the estimated percentage of the observed difference in survival rates between women detected at the screen and a control group that is due to bias is between 33 and 42%.

Adult↗
PubMed1978

An analysis of the benefits of serial screening for breast cancer based upon a mathematical model of the disease.

A model of breast cancer is developed that consists of hypotheses about the age-specific incidence of the disease, the rate of disease progression, the tendency of the disease to be detected without benefit of regularly scheduled screening examinations, and prognosis related to the extent of disease at treatment. Parameters for the model are estimated from published data. The model is validated by comparing model predictions to data not used in parameterization. The model, under a variety of assumptions, is then used to analyze questions of interest about breast cancer screening strategies. These include the following: the benefits from screening with mammography and clinical examination as a function of the frequency and starting age of screening, the effect of different assumptions about radiation risks on the benefits of screening, the benefits from screening with mammography if yearly clinical examinations are performed, and the benefits from screening with mammography and clinical examination if self-examinations are performed.

Adult↗
PubMedDate not supplied

Length of stay as an outcome in an era of managed care. An empirical study.

Longer length of stay (LOS) in substance abuse treatment, a standard measure of treatment success, conflicts with pressures from managed care. To maintain LOS as an outcome, we identified, for four modalities, LOS categories such that program completion rates were relatively constant within category and differed among categories. We validated the cutoffs by showing that future utilization over a 2-year period by clients differed by category. Clients in the long-LOS category used the system in a way consistent with more successful treatment. Thus, rather than using increase in LOS as an outcome, one can use increase in the percentage of clients reaching the long-LOS category. Categories were developed and utilization analyzed for discharges from publicly funded Boston treatment programs between 1/92 and 12/94 from the following modalities: short-term residential (5,462 discharges), long-term residential (5,086 discharges), outpatient (13,656 discharges), and detox (19,965 discharges).

Female↗
PubMedDate not supplied

A deep model of the incidence of dental caries on proximal surfaces.

As a component of an analysis of the benefits of alternative frequencies of bitewing radiographs to detect dental caries, the authors developed and validated a model to generate an individual's probability distribution for new carious lesions in a year. The model postulates two sources of variability in caries incidence--differences in individuals' underlying caries susceptibilities and a random component. The model is used to examine the nature of caries risk over time. The large random fluctuations in an individual's caries susceptibility from year to year, combined with the random nature of caries attack, makes it difficult to predict future caries experience from the individual's caries experience in the recent past. By modeling the process giving rise to observed incidence data rather than focusing directly on the observed data, i.e., by developing a deep rather than a surface model, the authors have elucidated underlying disease dynamics and provided a basis for generalizing from the particular data used to develop the model.

Adolescent↗