Statistical cost-effectiveness analysis of two treatments based on net health benefits

Statistical methods for cost-effectiveness analysis (CEA) for two treatments that mimic the deterministic optimal rules of CEA are presented. In these rules the objective is to determine the treatment with the maximal effectiveness whose unit cost is less than an amount, lambda, that a decision-maker is willing to pay (WTP). This is accomplished by identifying the treatment with the largest positive net health benefit (NHB), which is a function of lambda, while controlling the familywise error rate both when the WTP value is given and when it is unspecified. Fieller's theorem is used to determine a region of WTP values where the NHBs of the treatments are not distinguishable. For each lambda outside of the confidence region, the larger treatment is identified. A newly developed one-tailed analogue of Fieller's theorem is used to determine the WTP values where a treatment's NHB is positive. The situation in which both treatments are experimental is distinguished from the case where one of the treatments is usual care. The one-tailed confidence region is used in the latter case to obtain the lambda values where the NHBs are not different, and determining the region of positivity of the NHBs may be unnecessary. An example is presented in which the cost-effectiveness of two antipsychotic treatments is evaluated.

Efficacy of a single diagnostic test for sensitization to common inhalant allergens

BACKGROUND

UniCAP Phadiatop is a single laboratory test designed to determine the presence or absence of specific IgE to a variety of common inhalants. Its purpose is to aid in the differentiation of patients with symptoms attributable to allergic disease from other common causes.

METHODS

Consecutive children and adolescent patients (n = 145) at two centers were examined by having their history and physical examination performed by two board certified allergists. Their conclusions along with skin prick tests and specific IgE measurements regarding seven common inhalants (mite, oak, ragweed, grass, dog, cat, Alternaria) were compared with UniCAP Phadiatop test results. This was done using concordance of all test results. Attempts to resolve test discrepancies, when found, included specific RAST inhibitions, total IgE values, and physicians' judgment after testing.

RESULTS

All patients with resolved diagnoses (143 of 145, 103 positive and 40 negative) were identified correctly by the UniCAP Phadiatop test. Skin test results and specific IgE measurements correlated well, but neither correlated well with the history by itself, suggesting a minimal false-positive component of the history of 23%. UniCAP Phadiatop results demonstrated a quantitative relationship between the patient's score and the amount of IgE specific to these individual allergens.

CONCLUSIONS

The UniCAP Phadiatop test was shown to be highly sensitive and specific in differentiating individuals who are sensitized to common inhalants from those who are not. This test is recommended to all physicians as an aid in diagnostic and referral decisions for patients suspected of having an inhalant allergic diathesis.

Performance measures of cultural competency in mental health organizations

The authors utilized numerous documents created by advisory groups, expert panels and multicultural focus groups to develop performance measures for assessing the cultural competency of mental health systems. Competency was measured within three levels of organizational structure: administrative, provider network, and individual caregiver. Indicators, measures and data sources for needs assessment, information exchange, services, human resources, plans and policies, and outcomes were identified. Procedures for selection and implementation of the most critical measures are suggested. The products of this project are broadly applicable to the concerns of all cultural groups.

Novel cannabinol probes for CB1 and CB2 cannabinoid receptors

The observation that the phenolic hydroxyl of THCs was important for binding to the CB1 receptor but not as critical for binding to the CB2 receptor prompted us to extend this finding to the cannabinol (CBN) series. To study the SAR of CBN analogues, CBN derivatives with substitution at the C-1, C-3, and C-9 positions were chosen since these positions have played a key role in the SAR of THCs. CBN-3-(1',1'-dimethylheptyl) analogues were prepared by sulfur dehydrogenation of Delta(8)-THC-3-(1',1'-dimethylheptyl) analogues. 9-Substituted CBN analogues were prepared by the standard sulfur dehydrogenation of 9-substituted Delta(8)-THC analogues (Scheme 1), which in turn were prepared following our previous procedure using selenium dioxide oxidation of the corresponding Delta(8)-THCs followed by sodium chlorite oxidation to give the 9-carboxy-Delta(8)-THC derivatives. 11-Hydroxy-CBN analogues were prepared from the corresponding 9-carbomethoxy-CBN analogues by reduction with LiAlH(4). Deoxy-CBN analogue 14 was prepared from the corresponding Delta(8)-THC analogue 11 by conversion of the phenolic hydroxyl to the phosphate derivative 12, followed by lithium ammonia reduction to provide the deoxy-Delta(8)-THC analogue 13, which in turn was dehydrogenated with sulfur to provide the deoxy-CBN analogue 14 (Scheme 2). The various analogues were assayed for binding both to the brain and the peripheral cannabinoid receptors (CB1 and CB2). We have found that the binding profile differs widely between the CBN and the THC series. Specifically, in the CBN series the removal of the phenolic hydroxyl decreases binding affinity to both the CB1 and CB2 receptors, whereas in the THC series, CB1 affinity is selectively reduced. Thus, in the CBN series, the selectivity of binding observed with the removal of the hydroxy group is decreased severalfold as compared to what occurs in the THC series. Generally, high affinity for the CB2 receptor was found in analogues when the phenolic hydroxyl was present. The 3-(1', 1'-dimethylheptyl) derivatives were found to have much higher affinities than the CBN analogues, which is in complete agreement with previously reported work by Rhee et al.

Assessing the onset of relief of a treatment for migraine

It is common for clinical trials designed to compare treatments for migraine to incorporate a component for estimating onset. Our objective is to describe a stopwatch method for collecting data on time to meaningful relief and a conceptual framework for describing and analysing the results. The survival distribution of onset is modelled in two parts: the probability that onset does not occur, and the survival distribution conditional on its occurrence. Using data from a clinical trial comparing an active treatment and placebo, we illustrate the method and find that the distributions of onset among those with onset do not differ, but the probabilities that onset occurs are substantially different. We illustrate how the model can be used to help determine how long patients without onset should wait before further intervention, how patients interpret the phrase meaningful relief, and how baseline clinical characteristics affect the onset.

Talbot array illuminator for single-shot measurements of laser-induced-damage thresholds of thin-film coatings

A highly efficient Talbot array illuminator for single-shot, laser-induced-damage test measurements of optical thin-film coatings is proposed. With a periodic binary phase grating, a laser beam is transformed into an ensemble of Gaussian-like spots, which are known as the Fresnel image of the grating. For this purpose hexagonal phase gratings were fabricated and analyzed. With a peak fluence distribution of approximately 1 order of magnitude, the damage threshold of thin films can be deduced by use of the data from only a single shot.

Tenure in supportive housing for homeless persons with severe mental illness

OBJECTIVE

The study examined the long-term effectiveness of approaches to housing homeless persons with serious mental illness.

METHODS

A total of 2,937 persons placed in high-, moderate, -and low-intensity housing were followed for up to five years. Intensity reflected on the amount of structure and degree of clients' independence. The outcome variable was tenure in housing. Cox stepwise regression was used to calculate risk ratios of becoming discontinuously housed.

RESULTS

Thirty percent of the sample were initially placed in high-intensity settings, 18 percent in moderate-intensity settings, and 52 percent in low-intensity settings. Those in high-intensity settings tended to be younger, to be referred from hospitals, and to have a history or diagnosis of substance abuse. Individuals in moderate-intensity settings were more likely to be female and were least likely to have substance abuse problems. Individuals in low-intensity settings were more likely to be referred by municipal shelters and to have lived in municipal shelters for four or more months. After one, two, and five years, 75 percent, 64 percent, and 50 percent, respectively, of the sample were continuously housed. Older age was associated with longer tenure, and having a history of substance abuse was associated with shorter tenure. Individuals referred from a state psychiatric center had a greater risk of shorter tenure than other types of referrals.

CONCLUSIONS

Results show that homeless persons with serious mental illness can remain in stable housing for periods of up to five years, supporting the premise that long-term residential stability can be enhanced by providing access to safe and affordable supportive housing.

Power and sample size in cost-effectiveness analysis

For resource allocation under a constrained budget, optimal decision rules for mutually exclusive programs require that the treatment with the highest incremental cost-effectiveness ratio (ICER) below a willingness-to-pay (WTP) criterion be funded. This is equivalent to determining the treatment with the smallest net health cost. The designer of a cost-effectiveness study needs to select a sample size so that the power to reject the null hypothesis, the equality of the net health costs of two treatments, is high. A recently published formula derived under normal distribution theory overstates sample-size requirements. Using net health costs, the authors present simple methods for power analysis based on conventional normal and on nonparametric statistical theory.

Ratio-based and net benefit-based approaches to health care resource allocation: proofs of optimality and equivalence

Both incremental cost-effectiveness ratios and net benefits have been proposed as summary measures for use in cost-effectiveness analyses. We present a unifying proof of the optimality and equivalence of ICER- and net benefit-based approaches to the health resource allocation problem, including both 'fixed budget' and 'fixed price' decision rules. If internally consistent willingness-to-pay values are used, ratio- and net benefit-based decision rules identify the same optimal allocation. Because they have identical resource allocation implications, use of one or other of the two approaches must be based on other criteria, such as their behaviour under conditions of uncertainty.

Experimental determination of the fundamental-mode diameter in solid-state lasers

A method to determine directly the radius of the fundamental mode in a laser crystal has been developed. The radius is measured by comparison of the distribution of the spontaneous emission in the pumped region during laser operation with the fluorescence distribution without laser emission. Measuring the mode radius with various pump powers enables one to optimize the overlap between the pump and the cavity beam and to determine the dioptric power of the thermally induced lens.

Geographic analysis of pertussis infection in an urban area: a tool for health services planning

OBJECTIVE

This study examined whether incident cases of pertussis cluster in urban census tracts and identified community characteristics that predict high-incidence areas.

METHODS

An ecological study design was used. The study population included all persons diagnosed with pertussis from January 1, 1986, through December 31, 1994. Maps of rates were constructed via a geographic information system and clustering was statistically confirmed. Associations between pertussis rates and community characteristics were tested.

RESULTS

Mapping and statistical analysis revealed spatial clustering of pertussis. Higher age-adjusted rates of pertussis infection were associated with higher proportions of residents below poverty level.

CONCLUSIONS

In urban areas pertussis infection clusters in areas of poverty.

The cost and outcomes of community-based care for the seriously mentally ill

OBJECTIVE

To examine the cost-effectiveness of community-based mental health care.

DATA SOURCES/STUDY SETTING

Administrative data from Medicaid and the Massachusetts Department of Mental Health; primary data from 144 psychiatrically disabled adult Medicaid beneficiaries who lived in Boston, central Massachusetts, and western Massachusetts.

STUDY DESIGN

A cross-sectional observational study compared the costs and outcomes of treatment in three different types of public mental health service systems.

DATA COLLECTION/EXTRACTION METHODS

Beneficiaries, randomly sampled from outpatient mental health programs, were interviewed about their mental health status. All their acute treatment and long-term continuing care for the preceding year were abstracted from Medicaid and Department of Mental Health files. Costs were extracted from Medicaid paid claims and from Department of Mental Health contracts and other financial documents.

PRINCIPAL FINDINGS

Clients in the region allocating a greater proportion of its Department of Mental Health budget to community support services used far fewer hospital days, resulting in lower per person treatment expenditures. Outcomes, however, were not significantly different from outcomes of clients in the other regions. For all regions, substance abuse comorbidity increased hospitalization and total treatment costs. An individual-level cost-effectiveness analysis identified western Massachusetts (community-based care) as significantly more cost effective than the other two regions.

CONCLUSIONS

Systems with stronger community-based orientation are more cost effective.

The usefulness of average cost-effective ratios

We demonstrate that average cost-effectiveness ratios (CERs) play an important role in the evaluation of the cost-effectiveness of treatments. Criticisms of the usefulness of CERs derive mostly from the context of resource allocation under a constrained budget in which some decisions are based on incremental CERs. However, we show that in many cases, these decision rules are equivalent to decision rules on CERs. This follows for mutually exclusive treatments first, because a treatment is eliminated by extended dominance if and only if there is a mixed treatment with a smaller CER, where the mixing parameter lies in a certain interval. Second, after elimination of treatments by dominance and by extended dominance, resources can be allocated in order of increasing CERs. Moreover, the CER is a parameter that characterizes clinical and economical properties of a treatment independent of its comparators.

Statistical inference for cost-effectiveness ratios

Methods for statistical inference for cost-effectiveness (C/E) ratios for individual treatment and for incremental cost-effectiveness (delta C/ delta E) ratios when two treatments are compared are presented. In a lemma, we relate the relative magnitude of two C/E ratios to the delta C/ delta E ratio. We describe a statistical procedure to test for dominance, or admissibility, that can be used to eliminate an inferior treatment. The one-sided Bonferroni's confidence interval procedure is generalized to the two-sided case. The method requires only that two confidence intervals be available, one for cost and one for effectiveness. We describe Fieller-based confidence intervals and show them to be shorter than Bonferroni intervals. When distribution assumptions hold and variance and covariance estimates are available, Fieller intervals are preferable. However, Bonferroni intervals can be applied in more diverse situations and are easier to calculate. A simple Bonferroni based technique, and a likelihood ratio statistic given by Siegel, Laska and Meisner, for testing the null hypothesis that the C/E ratios of two treatments are equal is presented. The approaches are applied to the data from a phase II clinical trial of a new treatment for sepsis considered previously by others.

Biophysical characterization of cationic lipid: DNA complexes

To better understand the structures formed by the interaction of cationic lipids with DNA, we undertook a systematic analysis to determine the biophysical characteristics of cationic lipid:DNA complexes. Four model cationic lipids with different net cationic charge were found to interact in similar ways with DNA when that interaction was compared in terms of the apparent molar charge ratio of lipid to DNA. When DNA was present in charge excess over the cationic lipid, the complex carried a net negative charge as determined by zeta potential measurements. Under these conditions, some DNA was accessible to ethidium bromide, and free DNA was observed in agarose gels and in dextran density gradients. Between a lipid:DNA charge ratio of 1.25 and 1.5:1, all the DNA became complexed to cationic lipid, as evidenced by its inaccessibility to EtBr and its complete association with lipid upon agarose gel electrophoresis and density gradient separations. These complexes carried a net positive charge. The transition between negatively and positively charged complexes a occurred over a very small range of lipid to DNA ratios. Employing a fluorescent lipid probe, the addition of DNA was shown to induce lipid mixing between cationic lipid-containing vesicles. The extent of DNA-induced lipid mixing reached a maximum at a charge ratio of about 1.5:1, the point at which all the DNA was involved in a complex and the complex became positively charged. Together with freeze-fracture electron micrographs of the complexes, these biophysical data have been interpreted in light of the existing models of cationic lipid:DNA complexes.

Mental illness among homeless individuals in a suburban county

OBJECTIVE

This paper compares the prevalence of mental illnesses and alcohol and drug abuse and the residential histories of homeless individuals identified as having a mental illness and individuals who are not so identified. The cohort consisted of single persons applying for shelter over a 12-week period in Westchester County, a suburban county in New York State.

METHODS

The sample of 201 persons (89 percent male, with a mean age of 37) represented 77 percent of consecutive single shelter applicants in a single-point-of-entry system over the study period. Information from an intake assessment was augmented by a semistructured interview to reconstruct subjects' residential history for the last five years, including periods of homelessness and time in institutions.

RESULTS

Twenty-one percent of the cohort was classified as having mental illness. Seventy-two percent had a diagnosis of drug abuse or dependence, and 51 percent had alcohol abuse or dependence. For individuals with a mental illness, the use of cocaine and heroin was significantly lower, but alcohol use was somewhat greater, compared with other homeless persons. Persons with mental illness also experienced homelessness of some kind over a significantly longer period (a mean of seven years versus a mean of three years for other subjects), and they spent almost twice as many weeks during the previous five years literally homeless. Institutional time, most of which consisted of time in jail or prison, was equivalent for both groups.

CONCLUSIONS

Not only is residential instability heightened among shelter users with mental illness, but over time public institutions play a critical role in their accommodations. For some homeless persons with mental illness, the circuit of shelters, rehabilitation programs, jails, and prisons may function as a makeshift alternative to inpatient care or supportive housing and may reinforce the marginalization of this population.

Outcome in schizophrenia and related disorders compared between developing and developed countries. A recursive partitioning re-analysis of the WHO DOSMD data

BACKGROUND

Data on the two-year pattern of course of illness have been collected in the WHO study of the Determinants of Outcomes of Severe Mental Disorder (DOSMD). These data are reanalysed using recursive partitioning, a method not yet applied to psychiatric data to test the hypothesis that subjects from participating centres in developing countries had better outcomes than those in developed countries.

METHOD

Subjects were those from the DOSMD study for whom two-year follow-up data were available (n = 1056). The classification and regression trees recursive partitioning technique was used to examine the predictor variables associated with the outcome variable two year pattern of course.

RESULTS

Pattern of course was best predicted by centre, but two developed centres (Prague and Nottingham) grouped with the developing country centres excluding Cali, having better outcomes than in the remaining developed country centres and Cali. Type of onset (insidious v. non-insidious) was the next strongest predictor, but its effect differed across these two centre groupings. Effects for some groups were modified by other predictor variables, including age, child and/or adolescent problems, and gender.

CONCLUSIONS

The predominant predictor effects on two-year pattern of course continued to be centre and type of onset, but complex interactions between these variables and other predictor variables are seen in specific centre groupings not strictly defined by 'developing' and 'developed'.

Statistical methods for cost-effectiveness analyses

A statistical framework is presented for examining cost and effect data on competing interventions obtained from an RCT or from an observational study. Parameters of the join distribution of costs and effects or a regression function linking costs and effects are used to define cost-effectiveness (c-e) measures. Several new c-e measures are proposed that utilize the linkage between costs and effects on the patient level. These measures reflect perspectives that are different from those of the commonly used measures, such as the ratio of expected cost to expected effect, and they can lead to different relative rankings of the interventions. The cost-effectiveness of interventions are assessed statistically in a two stage procedure that first eliminates clearly inferior interventions. Members of the remaining admissible set are then rank ordered according to a c-e preference measure. Statistical techniques, particularly in the multivariate normal case, are given for several commonly used c-e measures. These techniques provide methods for obtaining confidence intervals, for testing the hypothesis of admissibility and for the equality of interventions, and for ranking interventions. The ideas are illustrated for a hypothetical clinical trial of antipsychotic agents for community-based persons with mental illness.

Long-term follow-up of schizophrenia in 16 countries. A description of the International Study of Schizophrenia conducted by the World Health Organization

An unexpected finding of the International Pilot Study of Schizophrenia, launched by the World Health Organization (WHO) in 1967, was that patients in countries outside Europe and the United States have a more favourable short- and medium-term course of the disease than those seen in developed countries. Since then, WHO has intensified its schizophrenia research programme and has initiated a set of international studies that have confirmed these initial findings and explored possible reasons for such differences in the course and outcome of schizophrenia. While such work has provided important findings and has generated additional pertinent hypotheses, it did not explain the differences in outcome. The present paper describes a new initiative in which approximately 2500 subjects involved in previous WHO multicentre schizophrenia studies are being followed up for between 15 and 25 years after initial examination. Nineteen research centres in 16 countries are taking part in this work. The research methodology is described.

Evaluation of agonist-antagonist properties of nitrogen mustard and cyano derivatives of delta 8-tetrahydrocannabinol

delta 8-Tetrahydrocannabinol (delta 8-THC) is a naturally occurring cannabinoid with a characteristic pharmacological profile of in vivo effects. Previous studies have shown that modification of the structure of delta 8-THC by inclusion of a nitrogen-containing functional group alters this profile and may alkylate the cannabinoid receptor, similar to the manner in which beta-funaltrexamine (beta-FNA) alkylates the micro-opioid receptor. Two novel analogs of delta 8-THC were synthesized: a nitrogen mustard analog with a dimethylheptyl side chain (NM-delta 8-THC) and a cyano analog with a dimethylpentyl side chain (CY-delta 8-THC). Both analogs showed high affinity for brain cannabinoid receptors and when administered acutely, produced characteristic delta 9-THC-like effects in mice, including locomotor suppression, hypothermia, antinociception and catalepsy. CY-delta 8-THC shared discriminative stimulus effects with CP 55,940; for NM-delta 8-THC, these effects also occurred, but were delayed. Although both compounds attenuated the effects of delta 9-THC in the mouse behavioral tests, evaluation of potential antagonist effects of these compounds was complicated by the fact that two injections of delta 9-THC produced similar results, suggesting that acute tolerance or desensitization might account for the observations. NM-delta 8-THC, but not CY-delta 8-THC, attenuated the discriminative stimulus effects of CP 55,940 in rats several days following injection. Hence, addition of a nitrogen-containing functional group to a traditional cannabinoid structure does not eliminate agonist effects and may produce delayed attenuation of cannabinoid-induced pharmacological effects.

Colorado pediatricians' involvement in community activities

To determine Colorado American Academy of Pediatrics (AAP) pediatricians' involvement in community-based activities and awareness of and interest in the AAP Community Access to Child Health (CATCH) program, a 22-item survey was mailed to all general pediatrician AAP fellows and candidate fellows practicing in Colorado (n = 434). The return rate was 65%. Of the respondents, 73% provide direct patient care as their primary professional activity, 58% reported either current or past involvement in community-based programs outside of their practices, 91% of this community-based work was voluntary, and 80% of the respondents described this work as moderate to very rewarding. Half of the respondents (51%) were aware of the AAP CATCH program, and 68% were interested in attending a statewide CATCH meeting. We conclude that Colorado AAP pediatrician survey respondents participate heavily in community programs outside of their clinical practices and that among this group there is substantial interest in the AAP CATCH program.

Simple designs and model-free tests for synergy

Current statistical designs for studying whether two or more agents in combination act synergistically nearly always require the study of several doses of many dose ratios. The analysis is usually based on an assumed parametric model of the dose-response surface. In this paper, for both quantal and quantitative response variables, sufficient conditions are given for establishing synergy at a dose of the combination without the need to specify the model. This enables the use of simple designs with few doses even when there is sparse knowledge of the dose-response curves of the individual agents. The Min test, used for testing whether an identified treatment is best, may be used for testing synergy. Power issues are discussed.

Retrograde ureteral intussusception

A soft tissue mass causing ureteral obstruction should be considered malignant until proved otherwise. We report a case of retrograde ureteral intussusception that caused obstruction. To our knowledge, this condition has not been described in the recent literature.