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Moscovice I, Wellever A, Sales A, Chen MM, Christianson J. A clinically based service limitation option for alternative model rural hospitals. HEALTH CARE FINANCING REVIEW 1993; 15:103-19. [PMID: 10135339 PMCID: PMC4193427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alternative model rural hospitals are designed to address problems faced by small, isolated rural hospitals. Typically, hospital regulations are reduced in exchange for a limit on the services that alternative models may offer. The most common service limitation is a limit on length of stay (LOS), a method with little empirical or conceptual support. The purpose of this article is to present a clinically based service limitation for alternative model rural hospitals, such as the rural primary care hospital. The proposal is based on an analysis of Medicare discharges from rural hospitals most likely to convert and the judgments of a technical advisory panel of rural clinicians.
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Chen MM, Jee WS, Ke HZ, Lin BY, Li QN, Li XJ. Adaptation of cancellous bone to aging and immobilization in growing rats. Anat Rec (Hoboken) 1992; 234:317-34. [PMID: 1443661 DOI: 10.1002/ar.1092340304] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two-and-half-month-old female rats were subjected to right hindlimb immobilization or served as controls for 0, 1, 2, 8, 14, and 20 weeks. The right hindlimb was immobilized by bandaging it against the abdomen, thus unloading it. Cancellous bone histomorphometry was performed on microradiographs and double-fluorescent labeled 20 microns sections of the distal femoral metaphyses. Primary spongiosa bone loss occurred rapidly by 2 weeks, and secondary spongiosa bone loss occurred rapidly by 8 weeks of immobilization, and then equilibrated at 60% less bone mass than age-related controls. The negative bone balance induced by immobilization was caused by transient increase in bone resorption, decrease in bone formation, and longitudinal bone growth. The dynamic data of secondary spongiosa cancellous bone showed that percent eroded perimeter was transiently elevated by 55 to 82% between 1 and 8 weeks, percent labeled perimeter was transiently depressed by 32% to 50% between 1 and 14 weeks, mineral apposition rate was depressed by 23% and 19% at 1 and 2 weeks, and bone formation rate-bone area referent was transiently depressed by 35% and 59% at 1 and 2 weeks. All the above parameters were at age-related control levels by 20 weeks of immobilization. However, bone formation rate-tissue area referent was depressed (-65%) throughout the study. Immobilization depressed completely longitudinal bone growth by 2 weeks and remained so. Only 0.65 mm of new metaphysis was generated in the immobilized versus 2.1 mm in controls during the study period. The immobilization induced an early cancellous bone loss which equilibrated at a new steady state with less bone and a normal (age-related control) bone turnover rate. When these findings were compared to an earlier study of 9-month-old virgin females subjected to right hindlimb immobilization up to 26 weeks, we found the adaptive responses of the cancellous bone were identical except that they occurred earlier and equilibrated sooner in younger rats.
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Arkin H, Holmes KR, Chen MM. A technique for measuring the thermal conductivity and evaluating the "apparent conductivity" concept in biomaterials. J Biomech Eng 1989; 111:276-82. [PMID: 2486365 DOI: 10.1115/1.3168379] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A simple technique for measuring thermal conductivity of biomaterials is described. The method is based on depositing a pulse of heat into the material of choice, and fitting the subsequent local temperature decay to that predicted by a theoretical model. This transient method is most suitable in situations where frequent measurements of the thermal conductivity are desired. The method was evaluated by calculating the thermal conductivity of several inert materials. The measured conductivities compared well with published values. The developed technique was also used to examine the applicability of the "apparent conductivity" index to combine both conductive and blood-convective thermal effects in living, blood perfused tissues. Using both simulated and experimental results, it was shown that the changes in the apparent conductivity are highly correlated with changes in blood flow. However, quantitative application of this index must be restricted to conditions that are similar to those which existed at the time the apparent conductivity was measured.
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Arkin H, Holmes KR, Chen MM. Theory on thermal probe arrays for the distinction between the convective and the perfusive modalities of heat transfer in living tissues. J Biomech Eng 1987; 109:346-52. [PMID: 3695437 DOI: 10.1115/1.3138692] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Recent suggestions for an improved model of heat transfer in living tissues emphasize the existence of a convective mode due to flowing blood in addition to, or even instead of, the perfusive mode, as proposed in Pennes' "classic" bioheat equation. In view of these suggestions, it might be beneficial to develop a technique that will enable one to distinguish between these two modes of bioheat transfer. To this end, a concept that utilizes a multiprobe array of thermistors in conjunction with a revised bioheat transfer equation has been derived to distinguish between, and to quantify the perfusive and convective contribution of blood to heat transfer in living tissues. The array consists of two or more temperature sensors one of which also serves to locally insert a short pulse of heat into the tissue prior to the temperature measurements. A theoretical analysis shows that such a concept is feasible. The construction of the system involves the selection of several important design parameters, i.e., the distance between the probes, the heating power, and the pulse duration. The choice of these parameters is based on computer simulations of the actual experiment.
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Arkin H, Holmes KR, Chen MM. Computer-based system for continuous on-line measurements of tissue blood perfusion. JOURNAL OF BIOMEDICAL ENGINEERING 1987; 9:38-45. [PMID: 3795903 DOI: 10.1016/0141-5425(87)90098-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We describe a new system for an almost continuous, on-line measurement of local blood perfusion in living tissue. The technique uses a thermal method based on measurements of the tissue temperature decay after a short pulse (approximately equal to 3 s) of local heating. The instrumentation system consists of six small thermistor microprobes, a probe interface unit and a DEC LSI-11/23 microcomputer. The system is equipped with six thermistor channels, and the number can be increased with further signal conditioning modules, thereby increasing the locations at which blood perfusion can be measured. The results agree favourably with values for tissue blood flow obtained simultaneously using either the microspheres method or an electromagnetic probe. The system has been in use for three years and there is good reason to believe that it can be reliably applied in many situations where a continuous multichannel monitor of local blood perfusion is necessary.
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Arkin H, Chen MM, Holmes KR. Adaptive thermal modeling: a concept for measurement of local blood perfusion in heated tissues. J Biomech Eng 1986; 108:306-11. [PMID: 3795874 DOI: 10.1115/1.3138619] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A new Adaptive Thermal Modeling (ATM) method for the measurement of local tissue blood perfusion rate is introduced. The method is based on a two-phase numerical technique. The first phase includes a fast, finite difference scheme for solution of the transient temperature field. The second phase involves iterative corrections of the perfusion until the modeled temperatures coincide with those measured by the temperature sensors. The results obtained from computer generated "data", as well as from laboratory experiments demonstrate the potential capability of the ATM method to continuously measure local perfusion rates in heated tissues. Rigorous analysis of the technique is planned for the near future so that it can be applied to in vivo measurements of local tissue blood perfusions.
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107
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Arkin H, Holmes KR, Chen MM, Bottje WG. Thermal pulse decay method for simultaneous measurement of local thermal conductivity and blood perfusion: a theoretical analysis. J Biomech Eng 1986; 108:208-14. [PMID: 3747464 DOI: 10.1115/1.3138604] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Presented here is a theoretical analysis of the recently developed thermal pulse decay (TPD) method for a simultaneous measurement of local tissue conductivity and blood perfusion rate. The paper describes the theoretical model upon which the TPD method is based and details its capabilities and limitations. The theoretical aspects that affected the development of the measurement protocol are also discussed. The performance of the method is demonstrated with an experimental example which compares the measurements of local kidney blood perfusion rates made using the TPD method with the total renal blood flow obtained coincidentally using a blood flowmeter, in an anesthetized dog.
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Arkin H, Holmes KR, Chen MM. A sensitivity analysis of the Thermal Pulse Decay method for measurement of local tissue conductivity and blood perfusion. J Biomech Eng 1986; 108:54-8. [PMID: 3959553 DOI: 10.1115/1.3138580] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Thermal Pulse Decay (TPD) method for the determination of local tissue thermal conductivity and blood perfusion rate is based on a comparison of measured with theoretically calculated temperatures. A sensitivity analysis of the theoretical model is performed. This analysis supports the establishment of an experimental protocol which reduces the measurement errors: An "optimal" measurement time interval for typical perfusion rates (up to 6 mL/mL/min) was found to be between 3 and 11 s after the heat pulse is turned off. Within this interval, the maximum error in determination of tissue conductivity and blood perfusion caused by experimental measurement errors is expected not to exceed 5 percent. The presently chosen pulse duration of 3 s is in agreement with the analysis as a good compromise between accuracy and excessive tissue heating.
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Adams T, Spielman WS, Holmes KR, Heisey SR, Chen MM. Proposed methods for the measurement of regional renal blood flow using heat transfer analysis. Ann Biomed Eng 1985; 13:237-58. [PMID: 3898927 DOI: 10.1007/bf02584242] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the renal cortex and medulla, and with its non-uniform blood vessel geometries, presents a unique challenge for measuring intrarenal blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate. Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat transfer equations to deduce regional blood flow by differentiating between heat dissipation due to local thermal conductivity and that attributable to the effects of regional convection. Although both methods are unavoidably invasive, neither produces debilitating damage in the tissue volume in which perfusion is measured, nor increases local temperature or metabolism enough to affect blood flow itself. Both techniques quantify local blood flow in small volumes of tissue by detailed evaluation of the many properties of tissue and blood which affect heat transfer, and both allow for a virtually unlimited number of nearly continuous sequential measurements at short (nom. 1 min) time intervals.
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Abstract
The effect of single-dose and multiple-dose cimetidine administration on acetaminophen pharmacokinetics was investigated in a three-phase, randomized, crossover study using four normal subjects. In each phase of the study, subjects ingested 750 mg of acetaminophen as a single dose alone (A), or in combination with 200 mg of cimetidine (A + C), or following a one-week pretreatment with daily cimetidine, 200 mg every six hours and 400 mg before retiring (A + C*). Statistical analysis using two-way analysis of variance indicated no significant difference in peak concentration and peak time of acetaminophen between treatments. Cimetidine did not significantly affect acetaminophen half-life, 2.38 hours (A), 2.65 hours (A + C), and 2.50 hours (A + C*). Acetaminophen clearance was minimally affected by cimetidine; the mean clearance of acetaminophen ranged from 4.16 (A + C*) to 5.57 mL/min/kg (A). Area under the acetaminophen plasma concentration-time curve was slightly increased by cimetidine, 35.4 (A), 41.6 (A + C), and 47.6 micrograms/mL/h (A + C*). Since cimetidine did not affect acetaminophen pharmacokinetics to any significant extent, clinical combination of both medications at therapeutic dosage presumably would not produce adverse interactions.
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Vanneste C, Chi CC, Brown KH, Callegari AC, Chen MM, Greiner JH, Jones HC, Kim KK, Kleinsasser AW, Notarys HA, Proto G, Wang RH, Yogi T. I-V characteristics of microwave-driven Josephson junctions in the low-frequency and high-damping regime. PHYSICAL REVIEW. B, CONDENSED MATTER 1985; 31:4230-4233. [PMID: 9936351 DOI: 10.1103/physrevb.31.4230] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Abstract
The absorption and disposition of ethambutol was examined in six rabbits in a three-way crossover study. Each rabbit received 45-mg/kg doses of ethambutol in three treatments: one intravenous injections and two oral solutions, ethambutol alone and ethambutol in the presence of aluminum hydroxide (40 mg/kg). Half-lives of ethambutol ranged from 2.26 to 5.20 h when administered alone and 2.18 to 4.00 h when coadministered with the antacid; the difference was not significant (p greater than 0.3). Mean clearance after the oral administrations (189.2 mL/min/kg) was significantly greater than the mean intravenous clearance (43.7 mL/min/kg) (p less than 0.01), suggesting a first-pass metabolism of ethambutol when administered nonparenterally to rabbits. The volume of distribution ranged from 5.5 to 17.8 L/kg, suggesting an extensive distribution of ethambutol outside the central compartment and, possibly, a localized deposit within the body tissues. Mean bioavailability of ethambutol was approximately 28% and was not affected by the presence of aluminum hydroxide. The rate of ethambutol absorption, however, was slightly delayed by the antacid.
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Holmes KR, Ryan W, Chen MM. Thermal conductivity and H2O content in rabbit kidney cortex and medulla. J Therm Biol 1983. [DOI: 10.1016/0306-4565(83)90014-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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114
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Chen MM, Lee C, Imamura Y, Perrin JH. Acetaminophen-aluminum hydroxide interaction in rabbits. J Pharm Sci 1983; 72:828-30. [PMID: 6886995 DOI: 10.1002/jps.2600720731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Acetaminophen-aluminum hydroxide interaction was investigated in a crossover study using six rabbits. Blood samples were collected at various time intervals for up to 6 hr following the oral administration of acetaminophen alone or in combination with aluminum hydroxide. Aluminum hydroxide at a 40-mg/kg dose did not appear to affect the rate and extent of acetaminophen absorption. The influence of aluminum hydroxide on gastric emptying could be compromised by gastric absorption of acetaminophen, resulting in a negligible effect on the overall bioavailability of acetaminophen.
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Tarng CM, Chen MM, Tsai WC. [Evaluation of the GNF computer-coding system for the identification of non-fermentative Gram-negative bacilli]. ZHONGHUA MINGUO WEI SHENG WU JI MIAN YI XUE ZA ZHI = CHINESE JOURNAL OF MICROBIOLOGY AND IMMUNOLOGY 1983; 16:71-83. [PMID: 6617315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In order to evaluate the effectiveness of the GNF computer-coding system for the identification of glucose non-fermenting gram-negative bacilli, we employed 406 strains of bacteria including 367 clinical isolates and 39 standard strains for testing. These strains were inoculated into the following eleven conventional biochemical test media: Triple Sugar Iron Agar, Simmon's Citrate Agar, Christensen's Urea Agar, Sulfide-Indole-Motility Medium, Semisolid Voges-Proskauer Test Medium, Moeller's Ornithine Decarboxylase Test Medium, Pyocyanin Test Medium, Oxidation/Fermentation (O/F) Glucose, O/F Fructose, Nitrate Broth, Moeller's Arginine Dihydrolase Test Medium. The results of these tests plus those from the hanging drop motility test and the oxidase test were converted into bacterial code number and then checked with the GNF computer-coding system. It was found that the first preference of agreement was 75.6%, second 15.3%, third 5.9%, and fourth or more 3.2%. In regard to the speed of bacterial identification by using the GNF system and information from hemolysis pattern and flagella stain, it was indicated that 84.7% would be correctly identified within 36-48 hours after isolation. If more confirmational tests were employed, the accurate identification rate would reach to 98.7% after 4 days of isolation. In addition, the use of the GNF computer-coding system can standardize identification procedures, shorten the identification period, and save cost in terms of materials supply, inoculation time, media preparation and media-storing space. Therefore, we conclude that the GNF computer-coding system is an effective tool in the identification of the glucose non-fermenting gram-negative bacilli.
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Chen MM, Holmes KR, Rupinskas V. Pulse-decay method for measuring the thermal conductivity of living tissues. J Biomech Eng 1981; 103:253-60. [PMID: 7311491 DOI: 10.1115/1.3138289] [Citation(s) in RCA: 83] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The present communication presents a single microprobe technique for measuring tissue thermal properties based on the dissipation of a measured amount of energy and the observation of the resulting temperature rise a given time later. An advantage of this method is that the effective sampling volume can be varied by varying the measurement time. Using a measurement time of a few seconds, the sampling volume was estimated to be several orders of magnitude greater than the probe volume. Hence artifacts due to probe-induced trauma or stress would be insignificant. Additional advantages of the technique are: the results were independent of the probe shape, size and properties, and hence represents absolute measurements without the need for calibration; the required electronics and computations are simple; the determination of thermal conductivity requires only a single measurement; and comparison of data at different measurement times yields a clear and unequivocal indication of nonconductive contributions of heat transfer, if present.
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Chen MM, Bush JW. Maximizing health system output with political and administrative constraints using mathematical programming. INQUIRY : A JOURNAL OF MEDICAL CARE ORGANIZATION, PROVISION AND FINANCING 1976; 13:215-27. [PMID: 135728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Decisions about delivery programs to improve health status are characterized by indivisibilities or "lumpiness," interdependencies between case types with varying health output, high fixed costs, administrative constraints, and qualitative quity and political considerations. The nature of the constraints and the goal of health services strongly suggest a mathematical programming model to maximize a comprehensive measure of health status. In a previously unreported development, binary integer programming can be extended to consider shared fixed costs, a widespread problem in optimizing effectiveness measures such as health status. The model proposed here applies conceptually across all target populations and health programs and could be used to optimize the output of a total health system. The effects of such optimization would be appropriately reflected in the weighted life expectancy computed as a social indicator.
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Bush JW, Chen MM, Bush AS. No-fault malparactice insurance. Proximate cause and the quality of medical care. West J Med 1975; 122:262-70. [PMID: 1146300 PMCID: PMC1129702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
No-fault medical malpractice insurance has been proposed as an alternative to the present tort liability approach. Statistical examination of the concept of proximate cause reveals not only that the question of acceptable care, and therefore of fault, is unavoidable in identifying patients deserving compensation, but also that specifying fault in an individual case is scientifically untenable. A simple formula for a Coefficient of Causality clarifies the question of proximate cause in existing trial practices and suggests that many of the threats associated with malpractice suits arise from the structure of the tort-insurance system rather than from professional responsibility for medical injury. The concepts could provide the basis for a revised claims and compensation procedure.
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Patrick DL, Bush JW, Chen MM. Toward an operational definition of health. JOURNAL OF HEALTH AND SOCIAL BEHAVIOR 1973; 14:6-23. [PMID: 4708414 DOI: 10.2307/2136932] [Citation(s) in RCA: 113] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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122
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Patrick DL, Bush JW, Chen MM. Methods for measuring levels of well-being for a health status index. Health Serv Res 1973; 8:228-45. [PMID: 4761617 PMCID: PMC1071759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Three psychological scaling procedures—category rating, magnitude estimation, and equivalence—were used to measure the levels of well-being that student and health-leader judges in 14 experimental groups associate with 50 case descriptions of function status representing the continuum from complete well-being to death. No significant differences were detected for order of method presentation, interview situation, scaling method, student vs. leader judges, or most interactions among these factors. Category rating, the simplest and apparently the most reliable of the methods, was consistent with the results of the social choices implied in the equivalence technique. The results indicate the feasibility of measuring the social values of large numbers of cases in household interview surveys.
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Huang LH, Sery TW, Chen MM, Cheung AS, Keeney AH. Experimental retinoblastoma. I. Morphology and behavior of cells cultivated in vitro. Am J Ophthalmol 1970; 70:771-7. [PMID: 5529277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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