Identifying subjects who benefit from additional information for better prediction of the outcome variables

Suppose that we are interested in using new bio- or clinical markers, in addition to the conventional markers, to improve prediction or diagnosis of the patient's clinical outcome. The incremental value from the new markers is typically assessed by averaging across patients in the entire study population. However, when measuring the new markers is costly or invasive, an overall improvement does not justify measuring the new markers in all patients. A more practical strategy is to utilize the patient's conventional markers to decide whether the new markers are needed for improving prediction of his/her health outcomes. In this article, we propose inference procedures for the incremental values of new markers across various subgroups of patients classified by the conventional markers. The resulting point and interval estimates can be quite useful for medical decision makers seeking to balance the predictive or diagnostic value of new markers against their associated cost and risk. Our proposals are theoretically justified and illustrated empirically with two real examples.

Human cytomegalovirus glycoprotein genotypes in the genital tract tissue of tubal pregnancy patients

This study investigated human cytomegalovirus (HCMV) glycoprotein genotypes in the genital tract tissue of 125 tubal pregnancy patients. The HCMV glycoprotein-B N-terminus (gBn, 54 - 485 NT), gB endoprotease cleavage site (gBclv, 1284 - 1600 NT) and glycoproteinH (gH, -58 - 213 NT) gene fragments were amplified by nested polymerase chain reaction and sequenced to identify gB and gH genotypes. Of 16 gBn-positive samples, four were gBn1, one was gBn2 and 11 were the gBn3 genotype. Of 13 positive gBclv samples, seven were gBclv1, two were gBclv2 and four were the gBclv3 genotype. Of 20 positive gH samples, 10 were gH1, six were gH2 and four were a combined gH1/gH2 genotype. In 10 of the samples that were positive for the gBn and gBclv genotypes, the gBn and gBclv genotypes were not consistent (four were gBclv1-gBn3). This study showed that: (i) HCMV infection with the gB1 - gB3 glycoprotein genotypes is present in tubal pregnancy; (ii) the gBclv and gBn genotypes are not strictly consistent; and (iii) intragenetic variability within the gB gene due to homologous recombination occurs frequently.

[Chronic prostatitis and biofilm]

Nowadays, inflammatory prostatic diseases represent one of the main social and economic problems that affect male gender in our country. The disease's prevalence is estimated at 11-14% in European countries, and males aged between 20 and 50 years are the most affected subjects. Bacterial prostatitis is documented at a very low prevalence (7-13% of prostatitis overall considered) due to either reduced utilization of viral and bacteriological tests (Meares test, urethral swab, bacterial and viral PCR) or to the possibility that individual patients show a scarce expression of bacterial disease in biological fluids, because of intraglandular biofilm presence, with subsequent spreading of the sole plankton microrganisms. Actually, the presence of a biofilm may possibly represent the reason for difficult diagnoses and ineffective antibacterial treatments.

A prediction model for type 2 diabetes risk among Chinese people

AIMS/HYPOTHESIS

A range of prediction rules for the onset of type 2 diabetes have been proposed. However, most studies have been conducted in white groups and it is not clear whether these models apply to Asian populations. The purpose of this study was to construct a simple points model for predicting incident diabetes among Chinese people.

METHODS

We estimated the 10 year risk of diabetes in a cohort study of middle-aged and elderly participants who were free from diabetes at baseline. Cox regression coefficients were used to construct the simple points model and the discriminatory ability of the resulting prediction rule was determined using AUC and net reclassification improvement and integrated discrimination improvement statistics. Fivefold random splitting was used to test the internal validity and obtain bootstrap estimates of the AUC.

RESULTS

Of the 2,960 participants without diabetes at the baseline examination, 548 developed type 2 diabetes during a median 10 year follow-up period. Age (four points), elevated fasting glucose (11 points), body mass index (eight points), triacylglycerol (five points), white blood cell count (four points) and a higher HDL-cholesterol (negative four points) were found to strongly predict diabetes incidence in a multivariate model. The estimated AUC for the model was 0.702 (95% CI 0.676-0.727). This model performed better than existing prediction models developed in other populations, including the Prospective Cardiovascular Münster, Cambridge, San Antonia and Framingham models for diabetes risk.

CONCLUSIONS/INTERPRETATION

We have constructed a model for predicting the 10 year incidence of diabetes in Chinese people that could be useful for identifying individuals at high risk of diabetes in the Chinese population.

Endocavitary Prophylaxis of Superficial Urothelial Bladder Tumours: New Compounds

Bladder urothelial carcinoma is the fourth most frequent cancer among European men, accounting for about 7% of the total cancers. Transurethral resection (TUR) is usually indicated as the standard treatment for non-muscle invasive bladder cancer (NMIBC). However, TUR is unable to guarantee a complete eradication of Ta, T1 tumors with a recurrence rate ranging from 50 to 70%, and a progression rate to muscle invasive disease ranging from 10 to 15%.

Methods

The European Association of Urology guidelines recommend adjuvant intravesical chemotherapy after definitive diagnosis of intermediate/high risk NMIBC to reduce both recurrence and progression of the disease. To provide a comprehensive review of intravesical treatment options for NMIBC, we performed a search of the PubMed database for articles between 1980 and 2009 that reported on intravesical agents for treating this disease.

Results

A critical analysis of the findings resulting from large multicenter trials, phase I, II, III studies for pertinent novel agents and from review articles was carried out. We focused on the following issues: 1) the role of the treatment with Bacillus Calmette-Guérin (BCG) and the need of maintaining the drug schedule (with or without interferon-alpha); 2) the correct timing of adjuvant immuno- and chemotherapy; 3) the use of the novel chemotherapeutic agents; 4) the use of the novel technique of chemotherapeutic agents administration, with a particular interest on electromotive administration of mitomycin.

[Endocavitary prophylaxis of superficial urothelial bladder tumours: new compounds]

Bladder urothelial carcinoma is the fourth most frequent cancer among European men, accounting for about 7% of the total cancers. Transurethral resection (TUR) is usually indicated as the standard treatment for non-muscle invasive bladder cancer (NMIBC). However, TUR is unable to guarantee a complete eradication of Ta, T1 tumors with a recurrence rate ranging from 50 to 70%, and a progression rate to muscle invasive disease ranging from 10 to 15%. METHODS. The European Association of Urology guidelines recommend adjuvant intravesical chemotherapy after definitive diagnosis of intermediate/high risk NMIBC to reduce both recurrence and progression of the disease. To provide a comprehensive review of intravesical treatment options for NMIBC, we performed a search of the PubMed database for articles between 1980 and 2009 that reported on intravesical agents for treating this disease. RESULTS. A critical analysis of the findings resulting from large multicenter trials, phase I, II, III studies for pertinent novel agents and from review articles was carried out. We focused on the following issues: 1) the role of the treatment with Bacillus Calmette-Guérin (BCG) and the need of maintaining the drug schedule (with or without interferon- alpha); 2) the correct timing of adjuvant immuno- and chemotherapy; 3) the use of the novel chemotherapeutic agents; 4) the use of the novel technique of chemotherapeutic agents administration, with a particular interest on electromotive administration of mitomycin.

Giant Stone in Enterocystoplasty

A giant stone in enterocystoplasty is a very rare condition; only 5 cases have been reported in the literature. A 50-year-old female with an enterocystoplasty due to congenital myelomeningocele presented at our institution for an asymptomatic 10-cm bladder stone, incidentally detected during an imaging procedure for uterine fibroma. The patient was treated with a laparoscopic hysterectomy with bilateral annexectomy, neocystotomy and stone removal under general anesthesia. The case report and an accurate literature review are reported. The incidence, risk factors, pathophysiology and treatment options are analyzed.

Robust combination of multiple diagnostic tests for classifying censored event times

Recent advancement in technology promises to yield a multitude of tests for disease diagnosis and prognosis. When there are multiple sources of information available, it is often of interest to construct a composite score that can provide better classification accuracy than any individual measurement. In this paper, we consider robust procedures for optimally combining tests when test results are measured prior to disease onset and disease status evolves over time. To account for censoring of disease onset time, the most commonly used approach to combining tests to detect subsequent disease status is to fit a proportional hazards model (Cox, 1972) and use the estimated risk score. However, simulation studies suggested that such a risk score may have poor accuracy when the proportional hazards assumption fails. We propose the use of a nonparametric transformation model (Han, 1987) as a working model to derive an optimal composite score with theoretical justification. We demonstrate that the proposed score is the optimal score when the model holds and is optimal "on average" among linear scores even if the model fails. Time-dependent sensitivity, specificity, and receiver operating characteristic curve functions are used to quantify the accuracy of the resulting composite score. We provide consistent and asymptotically Gaussian estimators of these accuracy measures. A simple model-free resampling procedure is proposed to obtain all consistent variance estimators. We illustrate the new proposals with simulation studies and an analysis of a breast cancer gene expression data set.

Epidemiology and risk factors in urolithiasis

Stone formation in the urinary tract affects about 5-10% of the population in industrialized countries, although it is very rare in other countries such as Greenland or Japan. The high incidence and recurrence rate contribute to making the urolithiasis a serious social problem. Nowadays, urolithiasis must be considered a 'disease in evolution' for several reasons, such as epidemiological changes, evolution of the methods used for diagnosis, and the treatment and prophylaxis of the population considered 'at risk' of stone disease. Some features of stone disease have changed over the last few years due to many social, economical and cultural factors that are described here. The increased prevalence of small urinary calculi has brought about a change in clinical symptoms, with frequent episodes of renal-ureteral colic, persistent pain and hydronephrosis. Similarly, the presence of residual fragments after extracorporeal shock wave lithotripsy has induced a radical change in the management of small calculi through the use of mini-invasive surgical techniques.

Predicting clustered dental implant survival using frailty methods

The purpose of this study was to predict future implant survival using information on risk factors and on the survival status of an individual's existing implant(s). We considered a retrospective cohort study with 677 individuals having 2349 implants placed. We proposed to predict the survival probabilities using the Cox proportional hazards frailty model, with three important risk factors: smoking status, timing of placement, and implant staging. For a non-smoking individual with 2 implants placed, an immediate implant and in one stage, the marginal probability that 1 implant would survive 12 months was 85.8% (95%CI: 77%, 91.7%), and the predicted joint probability of surviving for 12 months was 75.1% (95%CI: 62.1%, 84.7%). If 1 implant was placed earlier and had survived for 12 months, then the second implant had an 87.5% (95%CI: 80.3%, 92.4%) chance of surviving 12 months. Such conditional and joint predictions can assist in clinical decision-making for individuals.

Joint Inferences on Vaccine Efficacy Against Infection and Disease with Application to the First HIV Vaccine Efficacy Trial

In many clinical trials, subjects are followed for two stages of outcomes, and it is of interest to compare the incidence of each outcome between two randomized groups. The outcome of the first stage may influence the outcome of the second stage. Moreover, the relative risks of the two outcomes may be linked, with the time-dependent profile of relative risk for the second outcome functionally dependent on that of the first. For example, during exposure to HIV, virologic and host factors simultaneously impact the probability of infection and the subsequent viral trajectories, and the efficacy of a tested vaccine to prevent infection and to prevent viral failure may work in concert. We address this problem by modeling the relationship between the stage two hazard function and covariates via Cox's proportional hazards model (Cox, 1972), with the stage one log-hazard ratio theta(*) at the first event time Tl, included as a covariate. With theta(*) estimated using three methods, 1) nonparametric kernel smoothing; 2) locally parametric penalized splines; and 3) fully parametric cubic linear splines, we subsequently develop inference procedures for the regression parameter in the stage two Cox model based on each of the estimator of theta(*). The inferential procedures are studied in simulations and are illustrated with application to data from the world's first preventive HIV vaccine efficacy trial.

The IA-2 interactome

AIMS/HYPOTHESIS

Islet antigen-2 (IA-2), a major autoantigen in type 1 diabetes, is an enzymatically inactive member of the transmembrane protein tyrosine phosphatase (PTP) family. IA-2 is located in dense-core secretory vesicles and is involved in the regulation of insulin secretion. The present experiments were initiated to identify those proteins that interact with IA-2 (i.e. the IA-2 interactome) as a first step towards elucidating the mechanism(s) by which IA-2 influences insulin secretion and serves as an autoantigen.

MATERIALS AND METHODS

To determine the proteins with which IA-2 interacts, a yeast two-hybrid system was used to screen a human foetal library, and deletion mutants were used to determine the binding sites. Positive interactions were confirmed by immunoprecipitation pull-down experiments using cell lysate from transfected mammalian cell lines.

RESULTS

Six new interacting proteins were identified by this approach: mitogen-activated protein kinase-activating death domain (MADD), the MADD isoform IG20, PTPrho, PTPsigma, sorting nexin 19 (SNX19) and cyclophilin A. Using a series of IA-2 deletion mutants, we identified the regions on the IA-2 molecule to which five of the interacting proteins bound. Amino acids 744-979 of IA-2 were required for the maximum binding of MADD, IG20 and SNX19, whereas amino acids 602-907 of IA-2 were required for the maximum binding of PTPrho and PTPsigma. Pull-down experiments with cell lysate from transfected mammalian cells confirmed the binding of the interacting proteins to IA-2.

CONCLUSIONS/INTERPRETATION

The IA-2 interactome based on, pull-down experiments, currently consists of 12 proteins. The identification of these interacting proteins provides clues as to how IA-2 exerts its biological functions.

Quality of life after radical treatment of prostate cancer: Validation of the Italian version of the University of California-Los Angeles Prostate Cancer Index

OBJECTIVES

To validate an Italian version of the University of California-Los Angeles Prostate Cancer Index (UCLA-PCI).

METHODS

Men with prostate cancer treated with radical retropubic prostatectomy (RRP) or external beam radiation (EBR) were retrospectively selected. Each subject was asked to complete the UCLA-PCI short form and the 36-item short-form health survey (SF-36) questionnaires (principal sample); a subgroup completed both questionnaires twice (retest sample). A linguistic translation and validation was performed. Psychometric properties were analyzed.

RESULTS

A total of 595 men were included in the study: 394 from the Department of Urology (treated with RRP) and 201 from the Department of Radiotherapy (treated with EBR). Of these, 75 patients (50 from the RRP group and 25 from the EBR group) were selected as the retest cohort. Internal consistency reliability of the SF-36 and UCLA-PCI for the primary sample of the surgery and radiotherapy populations ranged from 0.82 to 0.94; the mean values of sexual function were superior in the principal urology group, whereas the principal radiotherapy group demonstrated superior mean values of urinary function and urinary bother. A strong correlation between urinary function and sexual and bowel function, and between urinary function and all bother scales, was reported only for patients treated with RRP. The expected correlation between sexual function and sexual bother was reported for the EBR group but not for the RRP group.

CONCLUSIONS

Our study demonstrated the excellent psychometric properties of the Italian version of the UCLA-PCI; the Italian version of the UCLA-PCI questionnaire will allow cross-cultural comparative studies in men with prostate cancer.