Pao-g Shen

Factors that affect recurrence after anterior colporrhaphy procedure reinforced with four-corner anchored polypropylene mesh

The purpose of this study was to evaluate the effectiveness of the anterior colporrhaphy procedure reinforced with four-corner anchored polypropylene mesh in patients with severe (stage III or IV) anterior vaginal prolapse. Thirty-eight consecutive women were enlisted for this prospective study. The procedure consisted of an extensive vaginal dissection to join the vesicovaginal and retropubic space and an anchoring of a polypropylene mesh patch between the two Arcus Tendineus Fasciae Pelvis in a tension-free manner. The mean age of the study group was 63 (33–80) years. The success rate was 87% (33/38) at a mean follow-up interval of 21 (12–29) months. A total of eight (100%) patients were also cured of concomitant stress incontinence (five overt and three occult type) with an additional tension-free vaginal tape (TVT) operation. During follow-up, there were five de-novo stress incontinence cases (16.7%) and four vaginal erosions of mesh (10.5%). Four clinical variables—diabetes mellitus, recurrent anterior vaginal prolapse, chronic cough and vaginal erosions of mesh—were found to have a significant correlation with an unsatisfactory surgical result with large values of hazard ratios found by survival analysis. We concluded that the anterior colporrhaphy procedure reinforced with four-corner anchored polypropylene mesh was effective for most, but failed in some patients who had specific risk factors within short convalescence periods. Concomitant stress incontinence can be successfully treated by a TVT operation in combination with the anterior colporrhaphy procedure reinforced with four-corner anchored polypropylene mesh. However, the anterior colporrhaphy procedure may itself have adverse effects on urethral sphincter function.

Semiparametric analysis of transformation models with doubly censored data

Double censoring arises when T represents an outcome variable that can only be accurately measured within a certain range, [L, U], where L and U are the left- and right-censoring variables, respectively. In this note, using Martingale arguments of Chen et al. [3], we propose an estimator (denoted by ˜β) for estimating regression coefficients of transformation model when L is always observed. Under Cox proportional hazards model, the proposed estimator is equivalent to the partial likelihood estimator for left-truncated and right-censored data if the left-censoring variables L were regarded as left-truncated variables. In this case, the estimator ˜β can be obtained by the standard software. A simulation study is conducted to investigate the performance of ˜β. For the purpose of comparison, the simulation study also includes the estimator proposed by Cai and Cheng [2] for the case when L and U are always observed.

The Product-Limit Estimate as an Inverse-Probability-Weighted Average

Abstract For randomly censored data, (Satten, G. A., Datta S. (2001). The Kaplan–Meier estimator as an inverse-probability-of-censoring weighted average. Amer. Statist. Ass. 55:207–210) showed that the Kaplan–Meier estimator (product-limit estimator (PLE)) can be expressed as an inverse-probability-weighted average. In this article, we consider the other two PLEs: the truncation PLE and the censoring-truncation PLE. For the data subject to left-truncation or both left-truncation and right-censoring, it is shown that these two PLEs can be expressed as inverse-probability-weighted averages.

Oxidative stress in nonallergic nasal polyps associated with bronchial hyperresponsiveness

Background:  Nasal polyposis (NP) is a chronic inflammatory disease of upper airway with unknown etiology. NP is frequently associated with asthma; the interaction between these comorbidities remains interesting. Oxidative stress has been implicated in the pathophysiology of NP and asthma. The aim of this study is to investigate the significance of oxidative stress in sinonasal microenvironments by evaluating its association with clinopathological parameters and its impacts on the pathogenesis of bronchial hyperresponsiveness (BHR) in NP.

Risk factors that affect the treatment of interstitial cystitis using intravesical therapy with a dimethyl sulfoxide cocktail

Introduction and hypothesisDimethyl sulfoxide (DMSO) bladder instillation is a standard therapy for interstitial cystitis (IC); however, there are varying degrees of success. We hypothesize that first-line intravesical therapy with a DMSO cocktail will optimize treatment outcome.MethodsNinety women with newly diagnosed IC were enrolled consecutively for the treatment. The IC symptom and problem index was used as an outcome measure.ResultsSix (6.7%) patients dropped out of the treatment due to intolerable bladder irritation. Fifty-five (65.5%) of the remaining 84 patients, who completed the treatment, experienced ≧50% symptomatic improvement. After a regression analysis, three clinical variables were found to affect treatment adversely, i.e., the presence of advanced cystoscopic glomerulations, microscopic hematuria, and urodynamic detrusor underactivity, respectively.ConclusionsOur results suggest bladder instillation with a DMSO cocktail may well be considered as first-line therapy for IC patients. However, there exists a subgroup of nonresponders who may have severe disease.

Estimation of the truncation probability with left-truncated and right-censored data

Let ( , , ) be i.i.d. random vectors such that ( , ) is independent of and . Let F, Q, and G denote the common distribution function of , , and , respectively. For left-truncated and right-censored data, one can observe nothing if and observe ( ), with and , if . A problem of interest is the estimation of the truncation probability . Under the constraint that , Wang [Wang, M.-C., 1991, Nonparametric estimation from cross-sectional survival data. Journal of Americal Statistical Association, 86, 130–143.] suggested estimating α by α n  = ∈ t [1−F n (s−)]dG n (s), where F n and G n are non-parametric maximum likelihood estimate of the distributions F and G, respectively. In this note, using inverse-probability-weighted estimators of F, G, and Q, we obtain two alternative representations, ˜α n and αˆ n , for α n . Simulation study shows that the estimator α n works satisfactorily for moderate sample size.

Analysis of two sling procedures using polypropylene mesh for treatment of stress urinary incontinence.

Objectives: To evaluate and compare the surgical outcome between the innovative tension‐free vaginal tape (TVT) and conventional pubovaginal sling (PVS) procedures using polypropylene mesh. Methods: Eighty consecutive women with urodynamic stress urinary incontinence (SUI), who chose to undergo either a TVT (n=23) or a PVS (n=57) procedure using polypropylene mesh based on financial consideration, were recruited for this study. The surgical results were analyzed and compared subjectively and objectively. Results: The mean follow‐up interval was 23 months for the TVT and 20 months for the PVS procedure (P=0.062). Postoperatively, SUI (91.3% vs. 93.0%), concomitant urge symptoms (85.0% vs. 85.3%) and the negative impact of incontinence and urogenital distress on patients’ quality of life (79.8% vs. 77.8%) (77.4% vs. 68.8%) had improved markedly. After a multivariable logistic regression analysis, the treatment outcome of SUI was found to be independent of the main effects of patient age, parity, concurrent gynecological surgeries, intrinsic sphincter deficiency, previous failed incontinence surgeries, and concomitant urge symptoms. However, it was significantly related to treatment procedures (TVT vs. PVS) and their interaction with patient body mass index (BMI). Based on the fitted logistic model, we see that TVT performs better than PVS when BMI is less than 27.27 kg/m2, and the advantage of TVT decreases as BMI increases. Conclusion: Both TVT and PVS procedures using polypropylene mesh are effective treatment modalities for female SUI. However, TVT was not as effective in treating overweight or obese women as PVS.

Semiparametric Analysis of Doubly Truncated Data

In many application, statistical data are frequently observed subject to a retrospective sampling criterion resulting in double-truncated data. For double-truncated data, the distribution of lifetime T is observable only when U ≤ T ≤ V, where U and V are the left-truncated and right-truncated time, respectively. Under the assumption of independence between T and (U, V), the nonparametric maximum likelihood estimate (NPMLE) of the distribution function of T (denoted by was developed by Efron and Petrosian (1999). For the special case V = U + d 0, when the distribution of U is parameterized as G(x; θ) and F is left unspecified, a semiparametric MLE estimator of F (denoted by can be obtained using the arguments similar to those of Wang (1989). Further, we can obtain interval estimation for F using the bootstrap method (Qin and Wang, 2001) or the semiparametric likelihood ratio (SLR) method proposed by Li et al. (1997). In this article, a simulation study is conducted to compare the performance between and . Besides, the bootstrap and SLR methods are used to construct confidence intervals for F(t). Simulation results show that when G(x; θ) is correctly specified the semiparametric MLE outpeforms the NPMLE and the semiparametric bootstrap and SLR methods are more efficient than the nonparametric bootstrap method.

Logistic regression analysis applied to cannibalism in the giant grouper Epinephelus lanceolatus fry

The giant grouper Epinephelus lanceolatus is a highly valued finfish. In past years, some propagation techniques such as induced spawning and sexual reversal were achieved. However, for hatcheries, the seed production is still unstable, and mass mortality often occurs. Serious intracohort cannibalism is one of the reasons for this. This fish exhibits type II cannibalism, and this type of cannibalism usually begins when growth heterogeneity among the fish appears. For hatcheries, routine size grading is themost commonly usedmethod to prevent this type of cannibalism. To establish an effective grading method, Hseu et al. developed a cannibal-prey length relationship from morphometric measurements for giant grouper fry:

Semiparametric analysis of randomized response data with missing covariates in logistic regression

In this article, two semiparametric approaches are developed for analyzing randomized response data with missing covariates in logistic regression model. One of the two proposed estimators is an extension of the validation likelihood estimator of Breslow and Cain [Breslow, N.E., and Cain, K.C. 1988. Logistic regression for two-stage case-control data. Biometrika. 75, 11-20]. The other is a joint conditional likelihood estimator based on both validation and non-validation data sets. We present a large sample theory for the proposed estimators. Simulation results show that the joint conditional likelihood estimator is more efficient than the validation likelihood estimator, weighted estimator, complete-case estimator and partial likelihood estimator. We also illustrate the methods using data from a cable TV study.