Biomedical subjects

Oliver M Bautista

Publications and source records attributed to Oliver M Bautista.

6 recordsLinked to original sources

PubMed2006

Parametric survival models for interval-censored data with time-dependent covariates.

We present a parametric family of regression models for interval-censored event-time (survival) data that accomodates both fixed (e.g. baseline) and time-dependent covariates. The model employs a three-parameter family of survival distributions that includes the Weibull, negative binomial, and log-logistic distributions as special cases, and can be applied to data with left, right, interval, or non-censored event times. Standard methods, such as Newton-Raphson, can be employed to estimate the model and the resulting estimates have an asymptotically normal distribution about the true values with a covariance matrix that is consistently estimated by the information function. The deviance function is described to assess model fit and a robust sandwich estimate of the covariance may also be employed to provide asymptotically robust inferences when the model assumptions do not apply. Spline functions may also be employed to allow for non-linear covariates. The model is applied to data from a long-term study of type 1 diabetes to describe the effects of longitudinal measures of glycemia (HbA1c) over time (the time-dependent covariate) on the risk of progression of diabetic retinopathy (eye disease), an interval-censored event-time outcome.

Biometry↗

PubMed2006

Baseline factors as predictors of clinical progression of benign prostatic hyperplasia in men treated with placebo.

PURPOSE: We analyzed data from the placebo arm of the MTOPS trial to determine clinical predictors of BPH progression. MATERIALS AND METHODS: A total of 3,047 patients with LUTS were randomized to either placebo, doxazosin (4 to 8 mg), finasteride (5 mg), or a combination of doxazosin and finasteride. Average length of followup was 4.5 years. The primary outcome was time to overall clinical progression of BPH, defined as either a confirmed 4-point or greater increase in AUA SS, acute urinary retention, incontinence, renal insufficiency, or recurrent urinary tract infection. We analyzed BPH progression event data from the 737 men who were randomized to placebo. RESULTS: The rate of overall clinical progression of BPH events in the placebo group was 4.5 per 100 person-years, for a cumulative incidence (among men who had at least 4 years of followup data) of 17%. The risk of BPH progression was significantly greater in patients on placebo with a baseline TPV of 31 ml or greater vs less than 31 ml (p <0.0001), a baseline PSA of 1.6 ng/dl or greater vs PSA less than 1.6 ng/dl (p = 0.0009), a baseline Qmax of less than 10.6 ml per second vs 10.6 ml per second or greater (p = 0.011), a baseline PVR of 39 ml or greater vs less than 39 ml (p = 0.0008) and baseline age 62 years or older vs younger than 62 years (p = 0.0002). CONCLUSIONS: Among men in the placebo arm, baseline TPV, PSA, Qmax, PVR and age were important predictors of the risk of clinical progression of BPH.

Adrenergic alpha-Antagonists↗

PubMed2006

Efficacy of human papillomavirus-16 vaccine to prevent cervical intraepithelial neoplasia: a randomized controlled trial.

OBJECTIVE: Human papillomavirus (HPV) virus-like particle (VLP) vaccines have demonstrated effectiveness in preventing persistent HPV infections. Whether protection lasts longer than 18 months and, thus, impacts rates of cervical intraepithelial neoplasia (CIN) 2-3 has not yet been established. We present results from an HPV16 L1 VLP vaccine trial through 48 months. METHODS: A total of 2,391 women, aged 16-23 years, participated in a randomized, double-blind, placebo-controlled trial. Either 40 mug HPV16 L1 VLP vaccine or placebo was given intramuscularly at day 1, month 2, and month 6. Genital samples for HPV16 DNA and Pap tests were obtained at day 1, month 7, and then 6-monthly through month 48. Colposcopy and cervical biopsies were performed if clinically indicated and at study exit. Serum HPV16 antibody titer was measured by radioimmunoassay. RESULTS: Among 750 placebo recipients in the per protocol population, 12 women developed HPV16-related CIN2-3 (6 CIN2 and 6 CIN3). Among 755 vaccine recipients, there were no cases (vaccine efficacy 100%, 95% confidence interval [CI] 65-100%). There were 111 cases of persistent HPV16 infection in placebo recipients and 7 cases in vaccine recipients (vaccine efficacy 94%, 95% CI 88-98%). After immunization, HPV16 serum antibody geometric mean titers peaked at month 7 (1,519 milli-Merck units [mMU]/mL), declined through month 18 (202 mMU/mL), and remained relatively stable between month 30 and month 48 (128-150 mMU/mL). CONCLUSION: The vaccine HPV16 L1 VLP provides high-level protection against persistent HPV16 infection and HPV16-related CIN2-3 for at least 3.5 years after immunization. Administration of L1 VLP vaccines targeting HPV16 is likely to reduce risk for cervical cancer. LEVEL OF EVIDENCE: I.

Adolescent↗

PubMed2003

The long-term effect of doxazosin, finasteride, and combination therapy on the clinical progression of benign prostatic hyperplasia.

BACKGROUND: Benign prostatic hyperplasia is commonly treated with alpha-adrenergic-receptor antagonists (alpha-blockers) or 5alpha-reductase inhibitors. The long-term effect of these drugs, singly or combined, on the risk of clinical progression is unknown. METHODS: We conducted a long-term, double-blind trial (mean follow-up, 4.5 years) involving 3047 men to compare the effects of placebo, doxazosin, finasteride, and combination therapy on measures of the clinical progression of benign prostatic hyperplasia. RESULTS: The risk of overall clinical progression--defined as an increase above base line of at least 4 points in the American Urological Association symptom score, acute urinary retention, urinary incontinence, renal insufficiency, or recurrent urinary tract infection--was significantly reduced by doxazosin (39 percent risk reduction, P<0.001) and finasteride (34 percent risk reduction, P=0.002), as compared with placebo. The reduction in risk associated with combination therapy (66 percent for the comparison with placebo, P<0.001) was significantly greater than that associated with doxazosin (P<0.001) or finasteride (P<0.001) alone. The risks of acute urinary retention and the need for invasive therapy were significantly reduced by combination therapy (P<0.001) and finasteride (P<0.001) but not by doxazosin. Doxazosin (P<0.001), finasteride (P=0.001), and combination therapy (P<0.001) each resulted in significant improvement in symptom scores, with combination therapy being superior to both doxazosin (P=0.006) and finasteride (P<0.001) alone. CONCLUSIONS: Long-term combination therapy with doxazosin and finasteride was safe and reduced the risk of overall clinical progression of benign prostatic hyperplasia significantly more than did treatment with either drug alone. Combination therapy and finasteride alone reduced the long-term risk of acute urinary retention and the need for invasive therapy.

5-alpha Reductase Inhibitors↗

PubMed2003

Group sequential large sample T2-like chi2 tests for multivariate observations.

In many studies, a K degree of freedom large sample chi2 test is used to assess the effect of treatment on a multivariate response, such as an omnibus T2-like test of a difference between two treatment groups in any of K repeated measures. Alternately, a K df chi2 test may be used to test the equality of K+1 groups in a single outcome measure. Jennison and Turnbull (Biometrika 1991; 78: 133-141) describe group sequential chi2 and F-tests for normal errors linear models, and Proschan, Follmann and Geller (Statist. Med. 1994; 13: 1441-1452) describe group sequential tests for K+1 group comparisons. These methods apply to sequences of statistics that can be characterized as having an independent increments variance-covariance structure, thus simplifying the computation of the sequential variance-covariance matrix and the resulting sequential test boundaries. However, many commonly used statistics do not share this structure, including a Liang-Zeger (Biometrika 1986; 73: 13-22) GEE longitudinal analysis with an independence working correlation structure and a Wei-Lachin (J. Amer. Statist. Assoc. 1984; 79: 653-661) multivariate Wilcoxon rank test, among others. For such analyses, this paper describes the computation of group sequential boundaries for the interim analysis of emerging results using K df tests that are expressed as quadratic forms in a statistics vector that is distributed as multivariate normal, at least asymptotically. We derive the elements of the covariance matrix of multiple successive K df chi2 statistics based on established theorems on the distribution of quadratic forms. This covariance matrix is estimated by augmenting the data from the successive interim analyses into a single analysis from which the component sequential tests and their variance-covariance matrix can then be extracted. Boundary values for the sequential statistics can then be computed using the method of Slud and Wei (J. Amer. Statist. Assoc. 1982; 77: 862-868) or using the alpha-spending function of Lan and DeMets (Biometrika 1983; 70: 659-663) with a surrogate measure of information. An example is presented using the analysis of repeated cholesterol measurements in a clinical trial.

Biometry↗

PubMed2003

Study design of the Medical Therapy of Prostatic Symptoms (MTOPS) trial.

Alpha-blockers and 5-alpha-reductase inhibitors are medical therapies that are being used as alternatives to surgical interventions to relieve symptoms of benign prostatic hyperplasia (BPH). Taken as monotherapy, alpha-blockers and 5-alpha-reductase inhibitors have each been shown to provide relief from BPH symptoms. Treatment with finasteride over 4 years has been shown to reduce both BPH symptoms and the likelihood of acute urinary retention and the need for surgery. Direct comparison of the alpha-blocker terazosin with finasteride has been done, but only for a period of 1 year. The Medical Therapy of Prostatic Symptoms (MTOPS) trial is a multicenter, randomized, placebo-controlled, double-masked clinical trial designed to evaluate the long-term efficacy of the alpha-blocker doxazosin and the 5-alpha-reductase inhibitor finasteride, whether taken as a monotherapy or in combination, in preventing or delaying the progression of BPH. We describe in this paper the design of the MTOPS trial, the concept of BPH progression, the definition and methods of determining the primary outcome events and the proposed statistical analysis methods. A unique feature of MTOPS is the inclusion of prostate biopsies on a subgroup of randomized participants. Volunteers among randomized participants are to undergo a biopsy of the prostate at predetermined time points during the trial. Studies that will be conducted using the tissue specimens collected in MTOPS can potentially provide information at the molecular level on the natural history of BPH among medically treated and untreated men with moderate to severe symptoms of BPH.

Data Collection↗