Nonparametric inference for median costs with censored data

Increasingly, estimations of health care costs are used to evaluate competing treatments or to assess the expected expenditures associated with certain diseases. In health policy and economics, the primary focus of these estimations has been on the mean cost, because the total cost can be derived directly from the mean cost, and because information about total resources utilized is highly relevant for policymakers. Yet, the median cost also could be important, both as an intuitive measure of central tendency in cost distribution and as a subject of interest to payers and consumers. In many prospective studies, cost data collection is sometimes incomplete for some subjects due to right censoring, which typically is caused by loss to follow-up or by limited study duration. Censoring poses a unique challenge for cost data analysis because of so-called induced informative censoring, in that traditional methods suited for survival data generally are invalid in censored cost estimation. In this article, we propose methods for estimating the median cost and its confidence interval (CI) when data are subject to right censoring. We also consider the estimation of the ratio and difference of two median costs and their CIs. These methods can be extended to the estimation of other quantiles and other informatively censored data. We conduct simulation and real data analysis in order to examine the performance of the proposed methods.

FDG-PET study of the bilateral subthalamic nucleus stimulation effects on the regional cerebral metabolism in advanced Parkinson disease

The aim of the study was to evaluate the changes in regional cerebral metabolic rate of glucose (rCMRGlu) induced by bilateral subthalamic nucleurs (STN) stimulation in advanced Parkinson's disease (PD). 18F-Fluorodeoxyglucose (FDG) PET data obtained before and one month after stimulation were analyzed with statistical parametric mapping (SPM). As a result of clinically effective bilateral STN stimulation, rCMRGlu increased in lateral globus pallidus (GP), upper brain stem, dorsolateral prefrontal cortex (DLPFC) and posterior parietal-occipital cortex, and decreased in the orbital frontal cortex and parahippocampus gyrus (p < 0.001). We conclude that the alleviation of clinical symptoms in advanced PD by bilateral STN stimulation may be the result of activation of both ascending and descending pathways from STN and of restoration of the impaired higher-order cortex functions.

Surface-Enhanced Raman Scattering of Pyridine Using Different Metals: Differences and Explanation Based on the Selective Formation of α-Pyridyl on Metal Surfaces

A simple method has been developed to produce SERS-active metal surfaces. Six metal surfaces (cadmium, nickel, gold, iron, copper, and silver) have been prepared on an aluminum foil underlayment by chemical reduction and strong surface-enhanced Raman signals have been observed for pyridine species on these surfaces. This permits the direct comparison of pyridine spectra on different metal surfaces prepared by the same chemically clean method. The differences among the SER spectra of the aqueous pyridine species using different metals generally follow the trend of silver, cadmium, nickel, iron, gold, and copper, which can be explained by the selective formation of alpha-pyridyl species and the equilibria between end-on adsorbed pyridines and edge-on adsorbed alpha-pyridyl species on the different metal surfaces.

High spatial resolution in vivo 2D (1)H magnetic resonance spectroscopic imaging of human muscles with a band-selective technique

This report demonstrates a 2D (1)H magnetic resonance spectroscopic imaging (MRSI) technique that can address some technical difficulties often encountered in MRS studies of human muscles. A preliminary application of this whole-slice technique in human skeletal muscles demonstrates clearly noticeable differences in (1)H metabolite spectra between different human muscles. This observation illustrates the importance of multi-voxel and high spatial resolution in a heterogeneous environment. This technique is robust, can be easily implemented on a commercial MR scanner, and should prove useful for investigators in both basic and clinical (1)H MRS studies.

Potential heating effect in the gravid uterus during MR HASTE imaging

Our purpose was to evaluate if temperature changes occur in maternal or fetal tissues during HASTE imaging.

METHODS

Pregnant pigs were scanned with the HASTE technique, and temperatures were measured with phase maps and temperature probes inserted into the amniotic fluid and fetal brain.

RESULTS

Fiberoptic probes showed that no heating occurred in fetal tissues or amniotic fluid during HASTE imaging.

CONCLUSION

Our current HASTE protocols do not deposit a significant amount of heat in the gravid uterus. J. Magn. Reson. Imaging 2001;13:856-861.

[The risk of sustained amenorrhea in patients with systemic lupus erythematosus receiving intermittent pulse cyclophosphamide therapy]

OBJECTIVE

To determine the risk of sustained amenorrhea in premenopausal women with systemic lupus erythematosus (SLE) receiving intermittent pulse cyclophosphamide (CTX) therapy.

METHODS

Prospectively comparing the amenorrhea rate of 51 cases receiving intermittent pulse cyclophosphamide therapy versus that of 22 cases receiving intermittent pulse methylprednisolone (MP) therapy.

RESULTS

The amenorrhea rate was higher in the CTX group (19.6%) than in the MP group (P = 0.025). In the CTX group, the amenorrhea rate of patients aged over 30 was higher than that of patients aged 30 or below 30 (P = 0.0018).

CONCLUSION

Pulse CTX therapy in fertile women with SLE is associated with increased rate of sustained amenorrhea, and the older the patient is, the higher risk for sustained amenorrhea the patient runs.

[Study on bolus cyclosphamide treatment for 64 cases of lupus nephritis]

OBJECTIVE

To report on the dosing, efficacy and side-effects of bolus cyclosphamide treatment for lupus nephritis (LN).

METHODS

64 consecutive cases of LN with 10 or more erythrocytes per high-power field, proteinuria (> 1 g of protein per day) and serum creatinine increased (> 133 mumol/L) were treated by bolus therapy with cyclophosphamide (CTX) given monthly for 6 months and then quarterly for 18 months.

RESULTS

49 patients had renal remission (defined as < 10 erythrocytes per high-power field, absence of cellular casts, excretion of < 1 g of protein per day and normal serum creatinine). The mean of doses was 1.1 g for each time (0.6-1.6 g), the mean of times of bolus CTX needed was 3.6 (1-8 times). The adverse events were amenorrhea (in 41% female patients), herpes zoster (in 13% patients) and hemorrhagic cystitis (in 1 patient).

CONCLUSION

The results indicate that monthly bolus CTX therapy is effective and safe for patients with LN. Its adverse effect is relatively not a serious problem.

Water modeled signal removal and data quantification in localized MR spectroscopy using a time-scale postacquistion method

We have previously shown the continuous wavelet transform (CWT), a signal-processing tool, which is based upon an iterative algorithm using a lorentzian signal model, to be useful as a postacquisition water suppression technique. To further exploit this tool we show its usefulness in accurately quantifying the signal metabolites after water removal. However, due to the static field inhomogeneities, eddy currents, and "radiation damping," the water signal and the metabolites may no longer have a lorentzian lineshape. Therefore, another signal model must be used. As the CWT is a flexible method, we have developed a new algorithm using a gaussian model and found that it fits the signal components, especially the water resonance, better than the lorentzian model in most cases. A new framework, which uses the two models, is proposed. The framework iteratively extracts each resonance, starting by the water peak, from the raw signal and adjusts its envelope to both the lorentzian and the gaussian models. The model giving the best fit is selected. As a consequence, the small signals originating from metabolites when selecting, removing, and quantifying the dominant water resonance from the raw time domain signal are preserved and an accurate estimation of their concentrations is obtained. This is demonstrated by analyzing (1H) magnetic resonance spectroscopy unsuppressed water data collected from a phantom with known concentrations at two different field strengths and data collected from normal volunteers using two different localization methods.

[The correlation between anticardiolipin antibodies and disease activity in patients with systemic lupus erythematosus]

This study was conducted to determine the prevalence and clinical association of anticardiolipin antibodies (ACA) in serum of patients with systemic lupus erythematosus (SLE). ACA (IgG, IgA, IgM) was measured by enzyme-linked immunosorbent assay (ELISA) in the serum sample of 87 patients of SLE. The prevalence rates of ACAIgG, ACAIgA and ACAIgM were 62.1%, 52.9% and 35.6% respectively. The titers of ACAIgG and ACAIgM were positively correlated with the disease activity (r = 0.2763, P = 0.044; r = 0.3294, P = 0.018); ACAIgG, ACAIgA and ACAIgM were negatively correlated with complement C3 (r = -0.4737, P = 0.000; r = -0.2990, P = 0.017; r = -0.2758, P = 0.029); and ACAIgG was negatively correlated with complement C4 (r = -0.4079, P = 0.005). The titers of ACAIgA in patients with thrombosis was higher than that in patients without thrombosis. The patients with central nervous system involvement (CNS-SLE) had significantly higher ACAIgG and ACAIgM titers, compared with those without CNS-SLE. The results indicate there is a correlation between ACA titers and disease activity. In patients with thrombosis, the titer of ACAIgA is higher, and in patients with CNS-SLE, the titers of ACAIgG and ACAIgM are higher.

[Studies on chemical constituents of the roots of Gypsophila oldhamiana Miq]

OBJECTIVE

To separate compounds from the root of Gypsophila oldhamiana.

METHOD

Chemical and chromatographic methods were used to separate the compounds. IR, MS, NMR were used to determine the structures of compounds.

RESULT

Compound pentacosanoic acid, lacceroic acid, beta-sitosterol, alpha-spinasterol, daucosterol and sucrose were identified.

CONCLUSION

All the above compounds were obtained from this genus for the first time.

Trial of antiepilepsirine (AES) in children with epilepsy

Antieplepsirine (AES) is a new antiepileptic drug (AED) which was originally extracted from a Chinese folk remedy, and is now chemically characterized and synthesized. Its chemical structure is different from those of other available AEDs. Animal experiments involving AES demonstrated significant antiepileptic activity. Only a few clinical studies of AES with open trial have been resorted, none of which were on children. A 6.5 month, add-on, double-blind, placebo-controlled, randomized, cross-over study on AES (10 mg/kg per day) was conducted on epileptic children (aged 1-14 years) refractory to treatment with standard AEDs. The seizure frequency was recorded, and the blood levels of AES and other co-medicated AEDs (phenobarbital, phenytoin, carbamazepine and valproate) were determined. Although not planned, patients or parents were allowed to refuse to cross-over to the alternate therapy. The results were compared to the children who crossed-over as well as for the entire group during the first 3 months of randomized treatment. A total of 58 children entered, but only 34/58 children completed the cross-over study. The 24 children whose parents refused to let them be crossed-over continued the original study treatment (AES or placebo) for the entire 6 months. There was no statistically significant difference in seizure control when the entire group of 58 patients was compared to a parallel study group for the first 3 months of therapy (P = 0.178). There was a significant difference (P<0.01) in seizure control between AES and placebo treatment for the 34 patients who completed the entire cross-over study. No significant changes were seen in the blood level of other AEDs, and no serious acute side effects were observed. The results of the present study indicate the efficacy of AES for epileptic children with refractory seizures.

[Chemical constituents of Phyllanthus urinaria L. and its antiviral activity against hepatitis B virus]

Studies on the chemical constituents of Phyllanthus urinaria and its antiviral activity against hepatitis B virus were completed. Eleven compounds have been isolated. Two of them are new compounds methyl ester dehydrochebulic acid and methyl brevifolin carboxylate. Antiviral experiments on HBsAg in vitro and liver damage caused by CCl4 have shown that. Phyllanthus urinaria possesses antiviral activities against HBV.

Characterization of hydroxyapatite film with mixed interface by Ar+ ion beam enhanced deposition

Ar+ ion beam enhanced deposition (IBED) was used to produce a hydroxyapatite (HA) film on polished titanium substrates. In this study, the HA ceramic target was sputtered by an argon-ion beam with an energy of 1.5 KeV, and the sputtered film was intermittently bombarded by energetic argon-ions at 60 KeV. An effective Ca-Ti mixed layer produced by the energetic argon-ion bombardment was confirmed by using Auger electron spectroscopy. The characteristics of the deposited films were evaluated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. XRD analysis revealed that the as-deposited film was amorphous, and a hydroxyapatite-type structure was obtained from the post-heat treatment of the deposited films. SEM observations showed that no distinct difference in surface morphology was found between the as-deposited and heat-treated samples for Ar+ IBED films, suggesting a strongly bonded HA film on the titanium substrate. In comparison with the HA target, some chemistry alterations were brought about in the deposited films, such as the incorporation of CO3, the loss of the OH groups and some distortion of the phosphate lattice.

In vivo bone marrow lipid characterization with line scan Carr-Purcell-Meiboom-Gill proton spectroscopic imaging

Line scan Carr-Purcell-Meiboom-Gill spectroscopic imaging sequences have been used to extract lipid chemical composition indices in healthy adult bone marrow in the knee at 1.5 T. Since several spectroscopic echo readouts follow each excitation, the information acquired reflects a balance between spectral T2 decay processes and spectral resolution. To examine this balance in detail, data sets with two different echo spacings and spectral resolutions have been acquired to compare the information available from each in studies of bone marrow. Oils for which high field (7 T) proton spectra were recorded were used to evaluate the accuracy of lipid chemical composition indices extracted from the line scan Carr-Purcell-Meiboom-Gill spectroscopic imaging methods at 1.5 T. The extension of the method to fast spectroscopic imaging of bone marrow with multiple echoes is demonstrated.

Cytochrome P-450scc-mediated oxidation of (20S)-22-thiacholesterol: characterization of mechanism-based inhibition

(20S)-22-thiacholesterol (1) is found to be a potent competitive inhibitor of pregnenolone biosynthesis from cholesterol by purified reconstituted bovine adrenal cytochrome P-450scc. The apparent dissociation constant Kd, determined from difference spectra, is 0.6 microM, close to the value from kinetic studies for the apparent inhibition constant, Ki, of 0.8 microM. Studies of the time course of pregnenolone production indicate that under turnover conditions the competitive inhibitor (1) is converted to a tighter binding inhibitor, shown to be (20S,22R)-22-thiacholesterol S-oxide (4), with high diastereoselectivity and in a time-dependent manner. Both the diastereomeric sulfoxides, (20S,22S)-22-thiacholesterol S-oxide (3) and (20S,22R)-22-thiacholesterol S-oxide (4), exhibit properties consistent with their being competitive versus cholesterol, but the (22R)-sulfoxide (4) binds approximately 10 times more tightly than the (22S) diastereomer (3). The apparent Kd values of sulfoxides 4 and 3 are 0.1 and 1.14 microM, respectively. EPR and absorption spectroscopic studies of enzyme-inhibitor complexes suggest direct coordination of the oxygen atom of the (22R)-sulfoxide (4) with the catalytic heme center. This implies that the inhibitor operates by directly blocking further reaction at the active site heme group, with a substantial lifetime of the enzyme-inhibitor complex.

[Chemical components of the leaves of Pistacia Chinensis Bge]

Six compounds have been isolated from the leaves of Pistacia chinensis, a species of Anacardiaceae family. Their structures were identified on the basis of UV, IR, NMR, and MS as gallic acid, m-digallic acid, quercetin, 6-0-galloyl arbutin-quercitrin and quercetin-3-0(6''-galloyl)-beta-D-glucosides.

[Chemical constituents of the leaves of Crataegus pinnatifida Bge. var. major N. E. Br]

Compounds were isolated from the aqueous extract of the leaves of Crataegus pinnatifida var. major and seven of them were identified as 2-(4-hydroxybenzyl)malic acid, quercetin, hyperin, vitexin, rhamnosylvitexin, diethylamine hydrochloride and sorbitol respectively by UV, IR, NMR, MS, some chemical techniques by comparison with the standard spectra of known compounds.

Structural characterization of the isoenzymatic forms of human myeloperoxidase: evaluation of the iron-containing prosthetic group

Myeloperoxidase (MPO) from human neutrophils has been purified and found to exist in three isoenzymatic forms, resolved by ion exchange chromatography. In addition to differences in subunit size and cellular compartmentalization of the isoenzymes, differences have been reported in their activity and susceptibility to inhibition. The structural basis of these isoenzymes is unclear; we attempted to further define their functional characteristics and structural identity. First, we measured respective enzymatic activity using a panel of substrates; MPO I was found to have lower activity with some substrates (pyrogallol, guaiacol, potassium iodide [KI]), but similar activity to the other isoenzymes with 4-aminoantipyrine. These studies confirm that MPO I is enzymatically distinct from MPO II and MPO III. Next, we examined the structural basis of these differences by evaluating the iron-containing prosthetic group in each form using electron paramagnetic resonance (EPR) and determination of the pyridine hemochrome. No significant difference between the isoenzymes was noted in these parameters, suggesting that the prosthetic group is the same in each protein. The cause for any difference in enzymatic activity must lie then in variations extrinsic to the heme, and based on previous studies of the gene and protein analysis, the posttranslational modification of MPO must account for these isoenzymatic species.

Research note: sleep problems of normal Chinese adolescents

Eight hundred and forty-six Chinese adolescents were surveyed concerning sleep behaviours including insomnia, nightmares, somniloquism, somnambulism, bruxism, and enuresis. Bruxism was reported most frequently (22%) followed by somniloquism (17%) and insomnia (14.9%). Subjects were compared by sex, age, and rearing by parents or parent surrogates. Cross cultural comparisons and the possible significance of findings are discussed.

Patterns of psychiatric consultation in a Chinese general hospital

The authors conducted a study of psychiatric consultation in a Chinese general hospital. Seventy-five inpatients (0.74% of the patients in the hospital) were referred by different services over a 1-year period. Internal medicine referred the most patients, and organic brain syndromes were the most common diagnoses. Depression was not a frequent diagnosis, but neurasthenia was a fairly common one. None of the referred patients had a diagnosis of alcoholism, drug abuse, or personality disorder. The authors compare these data with those of Western studies and discuss the possible factors influencing psychiatric consultation in China.