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Biomedical subjects

M Krahn

Publications and source records attributed to M Krahn.

At least 19 recordsLinked to original sources
PubMed2005

The SARS outbreak in a general hospital in Tianjin, China -- the case of super-spreader.

Severe acute respiratory syndrome (SARS) is a newly emerged infectious disease with a high case-fatality rate and devastating socio-economic impact. In this report we summarized the results from an epidemiological investigation of a SARS outbreak in a hospital in Tianjin, between April and May 2003. We collected epidemiological and clinical data on 111 suspect and probable cases of SARS associated with the outbreak. Transmission chain and outbreak clusters were investigated. The outbreak was single sourced and had eight clusters. All SARS cases in the hospital were traced to a single patient who directly infected 33 people. The patients ranged from 16 to 82 years of age (mean age 38.5 years); 38.7% were men. The overall case fatality in the SARS outbreak was 11.7% (13/111). The outbreak lasted around 4 weeks after the index case was identified. SARS is a highly contagious condition associated with substantial case fatality; an outbreak can result from one patient in a relatively short period. However, stringent public health measures seemed to be effective in breaking the disease transmission chain.

Adolescent↗
PubMed2004

Improving the accuracy of long-term prognostic estimates in hepatitis C virus infection.

Obtaining unbiased estimates of HCV prognosis is difficult because of potential biases associated with study design and calculation methods. We propose a new method for estimating fibrosis progression rates. A Markov model with fibrosis health states (F0-F4) was created. The maximum likelihood method was used to estimate stage-specific progression rates. We compared the standard method to the new method using two well-known cohort studies. The known stage distribution at the end of follow-up was compared with stage predicted by the Markov model using both methods of calculating transition rates. We also compared rates obtained using both methods to known fibrosis rates in a series of Monte Carlo simulations. For Kenny-Walsh's study (1999), transition rates between F0-F1, F1-F2, F2-F3, and F3-F4 were 0.042, 0.045, 0.097 and 0.070 fibrosis units/year (new method) and 0.045 units/year (standard method). The new method predicted fibrosis stage and known transition rates in Monte Carlo simulations more accurately. The standard method underestimates 30-year cirrhosis rates by up to 40%. The new (Markov maximum likelihood or MML) method allows accurate estimation of stage-specific transition probabilities from the many studies in which only a single biopsy is available. Application of the method supports the hypothesis that rates of fibrosis vary between stages.

Biopsy↗
PubMed2003

Limb-girdle muscular dystrophy in a 71-year-old woman with an R27Q mutation in the CAV3 gene.

The authors report a 71-year-old woman with limb-girdle muscular dystrophy (LGMD) associated with an R27Q mutation in the CAV3 gene. Immunohistochemistry showed a >90% reduction of caveolin-3 on the sarcolemma by western blot, and anti-dysferlin immunoreactivity was reduced. This case emphasizes that an R27Q missense mutation in the CAV3 gene can lead to various clinical phenotypes including hyperCKemia, rippling muscle disease, distal myopathy, and LGMD1C.

Aged↗
PubMed2003

[Skin stem cells].

Explore the source record for details and available documents.

Cytological Techniques↗
PubMed2001

Preparation and x-ray structures of alkali-metal derivatives of the ambidentate anions [tBuN(E)P(mu-NtBu)2P(E)NtBu]2- (E = S, Se) and [tBuN(Se)P(mu-NtBu)2PN(H)tBu)]-.

The ambidentate dianions [(t)BuN(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu](2)(-) (5a, E = S; 5b, E = Se) are obtained as their disodium and dipotassium salts by the reaction of cis-[(t)Bu(H)N(E)P(mu-N(t)Bu)(2)P(E)N(H)(t)Bu] (6a, E = S; 6b, E = Se), with 2 equiv of MN(SiMe(3))(2) (M = Na, K) in THF at 23 degrees C. The corresponding dilithium derivative is prepared by reacting 6a with 2 equiv of (t)BuLi in THF at reflux. The X-ray structures of five complexes of the type [(THF)(x)()M](2)[(t)BuN(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu] (9, M = Li, E = S, x = 2; 11a/11b, M = Na, E = S/Se, x = 2; 12a, M = K, E = S, x = 1; 12b, M = K, E = Se, x = 1.5) have been determined. In the dilithiated derivative 9 the dianion 5a adopts a bis (N,S)-chelated bonding mode involving four-membered LiNPS rings whereas 11a,b and 12a,b display a preference for the formation of six-membered MNPNPN and MEPNPE rings, i.e., (N,N' and E,E')-chelation. The bis-solvated disodium complexes 11a,b and the dilithium complex 9 are monomeric, but the dipotassium complexes 12a,b form dimers with a central K(2)E(2) ring and associate further through weak K.E contacts to give an infinite polymeric network of 20-membered K(6)E(6)P(4)N(4) rings. The monoanions [(t)Bu(H)N(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu)](-) (E = S, Se) were obtained as their lithium derivatives 8a and 8b by the reaction of 1 equiv of (n)BuLi with 6a and 6b, respectively. An X-ray structure of the TMEDA-solvated complex 8a and the (31)P NMR spectrum of 8b indicate a N,E coordination mode. The reaction of 6b with excess (t)BuLi in THF at reflux results in partial deselenation to give the monolithiated P(III)/P(V) complex [(THF)(2)Li[(t)BuN(Se)P(mu-N(t)Bu)(2)PN(H)(t)Bu]] 10, which adopts a (N,Se) bonding mode.

Journal Article↗
PubMed2001

Preparation and X-ray structures of Cu(I), Ni(II), and Pd(II) (N,S) complexes of the monoanion [(tBuN)(S)P(mu-N(t)Bu)2P(S)(NH(t)Bu)]- and a Pt(II) (S,S') complex of the dianion [((t)BuN)(S)P(mu-N(t)Bu)2P(S)(N(t)Bu)]2-.

The metathetical reactions of the lithium derivative of the monoanion [((t)BuN)(S)P(mu-N(t)Bu)(2)P(S)(NH(t)Bu)](-) (L) with CuCl/PPh(3), NiCl(2)(PEt(3))(2), PdCl(2)L'(2) (L' = PhCN, PPh(3)), and PtCl(2)(PEt(3))(2) produced the complexes (PPh(3))CuL (5), NiL(2) (6), PdCl(L)(PPh(3)) (7), PdL(2) (8), and Pt(PEt(3))(2)[((t)BuN)(S)P(mu-N(t)Bu)(2)P(S)(N(t)Bu)] (9). The X-ray structures of 5, 6, and 8 reveal a N,S-coordination for the chelating monoanion L with the metal centers in trigonal planar, tetrahedral, and square planar environments, respectively. By contrast, the dianionic ligand in the square planar Pt(II) complex 9 is S,S'-chelated to the metal center. (31)P NMR spectra readily distinguish between the N,S and S,S' bonding modes, and, on that basis, N,S chelation is inferred for the Pd(II) complex 7. Crystal data: 5, monoclinic, P2(1)/c, a = 19.175(4) A, b = 20.331(4) A, c = 10.017(6) A, beta = 91.79(3) degrees, V = 3903(2) A(3), and Z = 4; 6, orthorhombic, Pbcn, a = 14.298(5) A, b = 15.333(5) A, c = 24.378(5) A, beta = 90.000(5) degrees, V = 5344(3) A(3), and Z = 4; 8, monoclinic, P2(1)/n, a = 13.975(3) A, b = 14.283(3) A, c = 15.255(4) A, beta = 116.565(18) degrees, V = 2723.5(11) A(3), and Z = 2; 9, monoclinic, P2(1)/n, a = 12.479(6) A, b = 21.782(7) A, c = 17.048(5) A, beta = 100.30(3) degrees, V = 4559(3) A(3), and Z = 4.

Journal Article↗
PubMed2000

Construction of the Patient-Oriented Prostate Utility Scale (PORPUS): a multiattribute health state classification system for prostate cancer.

Health status indexes, such as the EuroQol, consist of a health state classification system and a set of utility weights. Indexes measure quality of life using a 0-1 utility score. Utilities for outcomes in prostate cancer (PC) are of unique importance, but generic indexes do not represent PC outcomes (e.g., sexual, urinary, bowel dysfunction) well, and may not capture their full impact. As a step toward improved utility measurement, we constructed a classification system for PC. We generated items for each of six health domains and rated their importance using interviews with 10 clinical experts and 80 patients. Key concepts were selected for each domain using item importance weightings, and a set of predetermined criteria. Text was developed to express levels of severity within each domain. Experts and two additional groups of patients (n = 40, n = 96) evaluated textual clarity and endorsed the content validity of the instrument. The final system consists of 10 domains with 4-6 levels each. The content validity of the system was endorsed by patients and experts. In conjunction with a set of utility weights, it may be used to develop a health status index, to improve utility measurement in patients, and to serve as a short psychometric (nonutility) instrument.

Health Status Indicators↗
PubMed1999

Principles of economic evaluation in surgery.

This document reviews the key principles of economic evaluation as they pertain to the evaluation of surgical questions. It addresses the role of economic evaluation in health care decision making, describes the central issues in performing or evaluating an economic evaluation, and finally offers several examples of recent economic evaluations from the surgical literature. A concise annotated reference section is provided for those wishing to read further.

Cost-Benefit Analysis↗
PubMed1998

Monitoring of isotretinoin therapy by measuring the plasma levels of isotretinoin and 4-oxo-isotretinoin. A useful tool for management of severe acne.

BACKGROUND: Isotretinoin for oral therapy in severe acne conglobata and acne nodulocystica represents a significant achievement; however, the drug exerts several mucocutaneous and systemic adverse effects, besides its teratogenic potency. OBJECTIVE: The aim of this study was to investigate the plasma levels of isotretinoin and of 4-oxo-isotretinoin over long-term treatment of severe acne and to assess any correlation with the given dose, the clinical improvement and the occurrence of side effects. METHODS: Forty-one patients with severe acne and acne-related disorders were studied under long-term oral intake of isotretinoin. Therapeutic effects and side effects were evaluated prior, during and at the end of therapy. The plasma levels of isotretinoin and of its major metabolite 4-oxo-isotretinoin were measured by reversed-phase HPLC and were correlated with the administered oral dose and the number and frequency of side effects. RESULTS: Dose-dependent plasma levels of isotretinoin and its metabolite were observed. At a mean dosage of 0.75-1.0 mg/kg/day, 404 +/- 142 ng/ml were measured, whereas the plasma levels of 4-oxo-isotretinoin were 1-2x higher. The plasma levels correlated well with the orally administered dose of isotretinoin and the observed mucocutaneous side effects. CONCLUSION: The study demonstrates that measuring of the plasma levels may be a helpful tool to monitor the individual therapeutic dose regimen in patients with severe acne in order to minimize undesired side effects and to control oral intake.

Acne Vulgaris↗
PubMed1998

Costs and cost-effectiveness of a universal, school-based hepatitis B vaccination program.

OBJECTIVES: This study evaluated the costs and cost-effectiveness of a school-based grade 6 universal vaccination program against hepatitis B. METHODS: We performed a descriptive cost study and cost-effectiveness analysis of British Columbia's vaccination program for 1994 and 1995. Since 1992, public health nurses have administered hepatitis B vaccine to grade 6 students in schools. We measured costs of vaccine, vaccine administration, and net program costs and used a validated Markov model to calculate the cost-effectiveness of the program. RESULTS: Vaccinating each student cost $44, $24 of which was the cost of vaccine administration. The net cost was $9 per person; considering productivity costs, net savings were $75 per person. Marginal cost per life year gained was $2100. Universal adolescent vaccination is also economically attractive in the United States but less attractive in regions with incidence rates below 3 cases per 100,000 per year. CONCLUSIONS: Hepatitis B vaccine can be delivered in North American schools at a reasonable cost. Adolescent vaccination is economically attractive in North American regions of high and average incidence rates. Our analysis supports vaccination in adolescents who remain at risk for hepatitis B virus infection.

British Columbia↗
PubMed1993

Discounting in the economic evaluation of health care interventions.

Do economic theories that underlie discounting have specific implications for program evaluation in health? In this study, both the contemporary practice and the theoretical foundations of discounting are reviewed. The social discount rate controversy is considered, and the two major concepts (i.e., opportunity cost and time preference) involved in the formulation of a social discount rate are outlined. Also described are the arguments for discounting proposed by thinkers in non-economic disciplines. Finally, the implications of choosing a discount rate for evaluation of individual health care programs are considered. It is argued that the conventional practice of discounting all health care programs at a rate of 5% may not consistently reflect societal or individual preference. Specific recommendations arising from this paper are: 1) given the considerable disagreement at the theoretical level as to the appropriate social discount rate, analysts should be specific about what theoretical approach underlies their choice of rate, especially when the analytic result is sensitive to the discount rate; 2) the discount rate chosen should be appropriate for the perspective of the analysis (social vs. individual vs. institutional, etc.); 3) when appropriate, measures should be taken to avoid double discounting, because some health related outcome measures already incorporate individuals' time preference; and 4) it is suggested that the political process may serve as the appropriate means of reflecting social values in the choice of a discount rate. In addition, the authors argue that a consensus conference approach, with political participation, offers a flexible, pragmatic, and explicit way of synthesizing the empirical, normative, and ethical considerations that underlie choice of a discount rate.

Cost of Illness↗
PubMed1991

Comparison of an aggressive (U.S.) and a less aggressive (Canadian) policy for cholesterol screening and treatment.

OBJECTIVE: To determine the point at which adverse quality-of-life effects engendered by an aggressive cholesterol-lowering strategy dictate the use of a less aggressive approach. DESIGN: Decision analysis was used to compare the effects of the National Cholesterol Education Program (NCEP) guidelines, an aggressive program, with those of the Canadian Task Force on the Periodic Health Examination (CTF) guidelines, a more conservative program. Quality-adjusted life expectancy was calculated for a theoretical cohort of middle-aged men treated according to each program using Markov cohort analysis. MEASUREMENTS: Guidelines were applied to the population of the Lipid Research Clinics Coronary Primary Prevention Trial (LRC-CPPT), under the assumption that cholesterol levels had the distribution of the age- and sex-matched general population. Outcomes were calculated using a three-state (health, coronary heart disease, and death) Markov model. State transition probabilities were calculated using bivariate (age and cholesterol) proportional hazards and logistic regression functions. MAIN RESULTS: The result was a "toss-up"; the number of expected quality-adjusted life years was similar for both programs at all time intervals, although the conservative program was consistently slightly favored. The result was very sensitive to the disutility of dietary therapy (threshold value, 0.0014 compared with the baseline estimate of 0.02) but was also affected by the time frame of the analysis and the rate at which adverse effects of treatment decline. CONCLUSIONS: Even small disutilities associated with treatment may outweight the benefits of aggressive cholesterol-lowering strategies. Research should be directed toward measuring these disutilities and finding ways to reduce their size. Incorporation of the disutility of treatment into policy formulation may result in less interventionist and less costly policies.

Adult↗