Search PubMed⌕ Search

Biomedical subjects

J W Hogan

Publications and source records attributed to J W Hogan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Power and sample size.

Explore the source record for details and available documents.

Data Interpretation, Statistical↗
PubMed1998

Increasing efficiency from censored survival data by using random effects to model longitudinal covariates.

When estimating a survival time distribution, the loss of information due to right censoring results in a loss of efficiency in the estimator. In many circumstances, however, repeated measurements on a longitudinal process which is associated with survival time are made throughout the observation time, and these measurements may be used to recover information lost to censoring. For example, patients in an AIDS clinical trial may be measured at regular intervals on CD4 count and viral load. We describe a model for the joint distribution of a survival time and a repeated measures process. The joint distribution is specified by linking the survival time to subject-specific random effects characterizing the repeated measures, and is similar in form to the pattern mixture model for multivariate data with nonignorable nonresponse. We also describe an estimator of survival derived from this model. We apply the methods to a long-term AIDS clinical trial, and study properties of the survival estimator. Monte Carlo simulation is used to estimate gains in efficiency when the survival time is related to the location and scale of the random effects distribution. Under relatively light censoring (20%), the methods yield a modest gain in efficiency for estimating three-year survival in the AIDS clinical trial. Our simulation study, which mimics characteristics of the clinical trial, indicates that much larger gains in efficiency can be realized under heavier censoring or with studies designed for long term follow up on survival.

Acquired Immunodeficiency Syndrome↗
PubMed1997

S-Phase fraction, p53, and HER-2/neu status as predictors of nodal metastasis in early vulvar cancer.

OBJECTIVE: Our aim was to determine the value of the S-phase fraction, p53, and HER-2/neu status as predictors of inguinal nodal metastasis in early vulvar cancer. METHODS: The charts of 100 consecutive patients with invasive squamous cell cancer of the vulva were reviewed and a cohort of patients with clinical stage I or II disease treated primarily with radical surgery and inguinal node dissection was identified. Within this cohort, all node-positive patients were matched with node-negative controls by depth of invasion. Tumor from the 13 node-positive patients and 26 controls was then analyzed by flow cytometry and immunohistochemistry. RESULTS: The median value of the S-phase fraction was higher in tumor from patients with inguinal nodal metastasis (median, 18.2; 25th-75th percentile: 13.9-28.3) than in node-negative patients (median, 8.9; 25th-75th percentile: 5.4-15.6) (P = 0.01). The presence of the HER-2/neu immunopositivity was also found to be associated with nodal metastasis (OR 4.05, 95% CI 1.0-16.6), but we found no evidence that DNA index or the presence of p53 immunopositivity was associated with nodal metastasis. CONCLUSION: Early vulvar cancer patients with inguinal node metastasis have a significantly higher S-phase fraction and are more likely to have HER-2/neu immunopositivity when compared to those without nodal metastasis.

Carcinoma, Squamous Cell↗
PubMed1997

The impact of hydrosalpinx on successful pregnancy in tubal factor infertility treated by in vitro fertilization.

OBJECTIVE: To determine the impact of hydrosalpinx on pregnancy rates in patients undergoing IVF for infertility caused by tubal disease. DESIGN: Review of the records of all patients who had undergone IVF for tubal factor infertility at our institution between May 1988 and October 1994. SETTING: A university-sponsored, hospital-based IVF facility. PATIENT(S): Two hundred fifty patients were identified with infertility due to tubal disease; 67 of these had at least one documented hydrosalpinx whereas the remaining 183 did not. MAIN OUTCOME MEASURE(S): Numbers of oocytes retrieved and fertilized, the number of embryos transferred and implanting, and resulting pregnancy rates. RESULT(S): The groups were similar in age and cycle cancellation rates. The patients with hydrosalpinx had greater numbers of oocytes retrieved per cycle (15.0 versus 11.6) and embryos transferred per cycle then those without hydrosalpinges (4.21 versus 3.98). The hydrosalpinx group also undertook more cycles per patient (2.31 versus 1.96). Fertilization rates between the two groups were similar, but implantation rates were decreased in those with hydrosalpinx (8.5% versus 11.2%). CONCLUSION(S): Hydrosalpinx did not result in impaired ovarian stimulation or decreased oocyte fertilization. It did, however, interfere with implantation and reduce to some degree the success of IVF in achieving an ongoing pregnancy. The validity of routine salpingectomy for hydrosalpinx is debatable, but its use in selected individuals may well be appropriate.

Abortion, Spontaneous↗
PubMed1997

Day 3 serum inhibin-B is predictive of assisted reproductive technologies outcome.

OBJECTIVE: To determine if women with day 3 serum inhibin-B concentrations < 45 pg/mL (conversion factor to SI unit, 1.00) demonstrate a poorer response to ovulation induction and assisted reproductive technologies outcome relative to women with inhibin-B values > or = 45 pg/mL. DESIGN: Analysis of inhibin-B, FSH, and E2 concentrations in day 3 serum samples. SETTING: Academic clinical practice. PATIENT(S): One hundred fifty-six women who underwent 178 assisted reproductive technology (ART) cycles with luteal phase GnRH agonist suppression plus hMG and urofollitropin stimulation. MAIN OUTCOME MEASURE(S): Serum E2 on day of hCG, number of oocytes retrieved per patient, fertilization rate, cleavage rate, clinical pregnancy rate (PR) per initiated cycle, cancellation rate per initiated cycle, and spontaneous abortion rate. RESULT(S): Women with day 3 serum inhibin-B < 45 pg/mL demonstrated 70% of the E2 response, had 66.6% of the number of oocytes retrieved per patient, with 28% of the clinical PR per initiated cycle, and three times the cancellation rate per initiated cycle than women with day 3 inhibin-B > or = 45 pg/mL. After controlling for age, day 3 serum FSH, day 3 serum E2, patient cycle number, and method of ART, day 3 serum inhibin-B > or = 45 pg/mL was noted to be prognostic of the number of oocytes retrieved and clinical PR. The adjusted odds ratio of clinical pregnancy for those with day 3 serum inhibin-B > or = 45 pg/mL versus those with inhibin-B < 45 pg/mL was 6.8 (95% confidence interval 1.8 to 25.6). CONCLUSION(S): Women with low day 3 serum inhibin-B concentrations demonstrate a poorer response to ovulation induction and are less likely to conceive a clinical pregnancy through ART relative to women with high day 3 inhibin-B.

Adult↗
PubMed1997

Serum triple-marker screening in in vitro fertilization and naturally conceived pregnancies.

OBJECTIVE: To determine whether results of second-trimester maternal serum triple-marker screening for Down syndrome and open neural tube defects in singleton pregnancies conceived from in vitro fertilization (IVF) differ from those of pregnancies conceived spontaneously. METHODS: The screen-positive rates and triple-marker levels of patients conceiving singleton pregnancies by IVF were compared to age-adjusted standards. RESULTS: Sixty-nine singleton IVF pregnancies with maternal serum screening were identified. Twenty-one (30.4%) of the 69 IVF singleton pregnancies had a positive screen for Down syndrome compared with a 14.4% expected screen-positive rate for the maternal age distribution in our observed sample (P = .013). The screen-positive rate for open neural tube defects in the measured population was similar to anticipated values based on historic controls (5.8% in IVF patients versus 5.3% in the total population). The median levels of the triple markers were 0.95 multiples of the median (MoM) for alpha-fetoprotein (AFP), 0.90 MoM for unconjugated estriol (E3), and 1.22 MoM for hCG. CONCLUSION: The increased hCG levels as well as the slightly lower AFP and unconjugated E3 levels may contribute to the higher Down syndrome screen-positive rate in this IVF singleton population. These results may be due to the number of embryos transferred, the maternal hormonal environment of the IVF process, or other factors. Pregnancies conceived by IVF may be twice as likely to have a positive maternal serum screening test. As additional data are collected, corrected standards should be determined.

Adult↗
PubMed1997

Prognostic value of clinical variables in ovarian cancer.

OBJECTIVE: To test the hypothesis that clinical variables, including the patient's symptoms, symptom severity, and co-morbidity, affect the survival rate in patients with ovarian cancer. METHODS: We reviewed the records of 137 cases of ovarian cancer diagnosed and treated between January 1987 and June 1992, and extracted data regarding patients' demographic characteristics, symptoms, medical co-morbidity, stage of disease, tumor histology and grade, treatment, and clinical course. RESULTS: Once cases of borderline tumors were excluded, the overall 3-year and 4-year mortality rate were 38% and 49%, respectively. There was an decrease in 4-year survival with more advanced symptom type ranging from 85% in asymptomatic women to 38% in women with complex symptoms (log rank, p = 0.005). Medical co-morbidity was not found to affect survival in the cohort studied. We performed multivariable analysis using a Cox proportional hazards model and confirmed that the symptom stage was highly prognostic even after controlling for FIGO stage, age and co-morbidity (p = 0.004). CONCLUSION: We found that clinical variables such as patient's symptoms, were associated with prognosis. Symptom classification is a necessary and important component in a system of prognostic stratification for ovarian cancer.

Adolescent↗
PubMed1997

Age and stage of readiness for smoking cessation.

Using the 1992 National Health Interview Survey Cancer Control Supplement, relationships were analyzed between stage of readiness for smoking cessation and background characteristics, smoking behaviors, and smoking-related attitudes among smokers aged 18-29, 30-49, and > or = 50 years. For each age group, an ordinal logistic regression model was computed to identify correlates of readiness to quit. The youngest smokers had attitudes most favorable to being ready to try to quit smoking. For smokers aged 30-49, the influence of a medical provider and perceived health effects of smoking were important correlates of readiness. Among smokers 50 and older, those with realistic health consequences of smoking and those who perceived smoking as addictive were more likely to be ready to quit. The effectiveness of smoking cessation programs might be improved by matching interventions to a smoker's age and stage in the smoking cessation process.

Adolescent↗
PubMed1997

Closure of Pfannenstiel skin incisions. Staples vs. subcuticular suture.

OBJECTIVE: To compare skin closure with staples and subcuticular suture. STUDY DESIGN: Obstetric patients undergoing cesarean section with a Pfannenstiel incision were prospectively randomized to skin closure with staples or subcuticular suture. Pain and cosmesis were assessed postoperatively. RESULTS: Patients reported significantly less pain following subcuticular closure at both the time of discharge (P < or = .01) and the postoperative visit (P < or = .002). Incisions closed with subcuticular suture were found to be more cosmetically attractive by both patients (P = .04) and physicians (P = .01) at the postoperative visit. CONCLUSION: Pfannenstiel skin incisions closed with subcuticular closure following cesarean section result in less postoperative discomfort and are more cosmetically appealing at the six-week postoperative visit as compared to incisions closed with staples.

Cesarean Section↗
PubMed1996

Laboratory evaluation of acute upper genital tract infection.

OBJECTIVE: To evaluate the diagnostic test characteristics of common tests used to diagnose upper genital tract infection. METHODS: Subjects included women who either met the Centers for Disease Control and Prevention's minimal criteria for acute pelvic inflammatory disease or who had other signs of upper genital tract infection (i.e., atypical pelvic pain, abnormal uterine bleeding, or cervicitis). The subjects were evaluated with a baseline interview, comprehensive laboratory testing, and either an endometrial biopsy or laparoscopy for definitive diagnosis of upper genital tract infection. Patients were considered positive for upper genital tract infection if they had any of the following findings: 1) histologic evidence of acute endometriosis or salpingitis, 2) laparoscopic visualization of purulent exudate in the pelvis without another source, or 3) positive testing for Neisseria gonorrhoeae or Chlamydia trachomatis from the endometrium, fallopian tubes, or pelvis. RESULTS: One hundred twenty women with adequate endometrial samples were evaluated between August 1993 and September 1995. The median age of the study population was 24 years: 38% were white, 52% were smokers, 81% were insured by Medicaid or were uninsured, and 67% were single. Sensitivities for elevated white blood cell count (WBC), erythrocyte sedimentation rate, C-reactive protein, and increased vaginal white blood cells are 57, 70, 71, and 78%, respectively. If any one test is abnormal, the sensitivity is 100% and specificity is 18%. If all four tests are abnormal, sensitivity is 29% and specificity is 95%. CONCLUSION: Testing for increased vaginal white blood cells was found to be the most sensitive laboratory indicator for upper genital tract infection, whereas serum WBC was the most specific. No one diagnostic laboratory test is pathognomonic for upper genital tract infection. Combinations of positive tests can improve diagnostic specificity and positive predictive value, but with a diminution of sensitivity and negative predictive value. Combinations of negative tests can reliably exclude upper genital tract infection.

Acute Disease↗
PubMed1996

Intention-to-treat analyses for incomplete repeated measures data.

In a randomized longitudinal clinical trial designed to evaluate two or more rival treatments, an intent-to-treat analysis requires inclusion of all randomized patients, regardless of whether they remain on protocol for the duration of the study. We propose a piecewise linear random effects model for analyzing longitudinal data where the multivariate outcome can depend upon time spent on treatment. The model assumes that data are available on a random sample of subjects after treatment is terminated, and allows either a pragmatic or explanatory analysis (as defined by Schwartz and Lellouch, 1967, Journal of Chronic Diseases 20, 637-648). Full maximum likelihood estimation of the model parameters is carried out using widely available statistical software for repeated measures with missing data and for nonparametric survival curve estimation. Data from a national, multicenter pediatric AIDS clinical trial are analyzed to illustrate implementation and interpretation of the model.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Mixture models for the joint distribution of repeated measures and event times.

Many long-term clinical trials collect both a vector of repeated measurements and an event time on each subject; often, the two outcomes are dependent. One example is the use of surrogate markers to predict disease onset or survival. Another is longitudinal trials which have outcome-related dropout. We describe a mixture model for the joint distribution which accommodates incomplete repeated measures and right-censored event times, and provide methods for full maximum likelihood estimation. The methods are illustrated through analysis of data from a clinical trial for a new schizophrenia therapy; in the trial, dropout time is closely related to outcome, and the dropout process differs between treatments. The parameter estimates from the model are used to make a treatment comparison after adjusting for the effects of dropout. An added benefit of the analysis is that it permits using the repeated measures to increase efficiency of estimates of the event time distribution.

Algorithms↗