Contribution of the second stage of labour to pelvic floor dysfunction: a prospective cohort comparison of nulliparous women.

OBJECTIVE: Maternal expulsive efforts are thought to damage the pelvic floor. We aimed to compare pelvic floor function and anatomy between women who delivered vaginally (VB) versus those with caesarean delivery (CD) prior to the second stage of labour. DESIGN: Prospective cohort. SETTING: University Hospital Midwifery practice. POPULATION: Nulliparas. METHODS: Pregnant nulliparas were recruited during pregnancy and women who underwent CD prior to the 2nd stage of labour at birth were recruited immediately postpartum. Both groups were followed prospectively to 6 months postpartum. MAIN OUTCOME MEASURES: POPQ, perineal ultrasound (U/S) and Paper Towel Test (PTT), an objective measure of stress incontinence; Incontinence Severity Index (ISI), Pelvic Floor Impact Questionnaire (PFIQ-7), Wexner Fecal Incontinence Scale (W) and Female Sexual Function Index (FSFI). RESULTS: 336/448 (75%) VB and 138/224 (62%) CD followed up. The VB group was younger (23.9 ± 4.9 versus 26.6 ± 6.1 years, P < 0.001) and less overweight/obese (38 versus 56%, P < 0.001); baseline functional measures were similar (all P > 0.05). At follow-up, urinary incontinence (UI) (55 versus 46% ISI > 0, P = 0.10), fecal incontinence (FI) (8 versus 13% FI on W, P = 0.12), sexual activity rates (88 versus 92%, P = 0.18) and PFIQ-seven scores were similar. Positive PTT tests (17 versus 6%, P = 0.002) and ≥ Stage 2 prolapse (22 versus 15%, P = 0.03) were higher with VB; differences were limited to points Aa and Ba. U/S findings were not different between groups. Stepwise multivariate analyses controlling for age, body mass index, and non-Hispanic White race for prolapse of points Aa and Ba did not alter conclusions (all P < 0.004). CONCLUSIONS: VB resulted in prolapse changes and objective UI but not in increased self-report pelvic floor dysfunction at 6 months postpartum compared with women who delivered by CD prior to the second stage of labour. The second stage of labour had a modest effect on postpartum pelvic floor function.

A method for multi-group inter-participant correlation: abnormal synchrony in patients with schizophrenia during auditory target detection.

The general linear model (GLM) approach is the most commonly used method in functional magnetic resonance imaging analysis in predicting a particular response. Recently, a novel method of analysis, referred to as inter-participant correlation (IPC), was developed which attempts to determine the level of blood oxygen level-dependent (BOLD) synchrony among subjects. The IPC approach enables detection of changes in inter-participant BOLD synchrony in a manner that does not rely on an explicit model of the hemodynamic activity. In this paper, we extend IPC to the case of two groups and derive an approach for thresholding the resulting maps. We demonstrate our approach by comparing 35 patients with paranoid schizophrenia (DSM-IV sub-type 295.30) to 35 healthy matched controls during an auditory target detection paradigm. Results showed significantly lower inter-participant BOLD synchrony in patients versus healthy controls in areas including bilateral temporal lobes, medial frontal gyrus, anterior cingulate cortex, dorsolateral prefrontal cortex, thalamus, insula, and cerebellum. The IPC approach is straightforward to use and provides a useful complement to traditional GLM techniques. This approach may also be sensitive to underlying, but unpredictable, changes in inter-participant BOLD synchrony between patients and controls.

Mortality risk among hemodialysis patients receiving different vitamin D analogs.

Intravenous vitamin D is standard therapy for secondary hyperparathyroidism in hemodialysis (HD) patients. In for-profit dialysis clinics, mortality was higher for patients on calcitriol compared to paricalcitol. Doxercalciferol, a second vitamin D2 analog, is currently available. We assessed mortality associated with each vitamin D analog and with lack of vitamin D therapy in patients who began HD at Dialysis Clinic Inc. (DCI), a not-for-profit dialysis provider. During the 1999-2004 study period we studied 7731 patients (calcitriol: n=3212; paricalcitol: n=2087; doxercalciferol: n=2432). Median follow-up was 37 weeks. Mortality rates (deaths/100 patient-years) were identical in patients on doxercalciferol (15.4, 95% confidence interval (13.6-17.1)) and paricalcitol (15.3 (13.6-16.9)) and higher in patients on calcitriol (19.6 (18.2-21.1)) (P<0.0001). In all models mortality was similar for paricalcitol versus doxercalciferol (hazard ratios=1.0). In unadjusted models, mortality was lower in patients on doxercalciferol (0.80 (0.66, 0.96)) and paricalcitol (0.79 (0.68, 0.92)) versus calcitriol (P<0.05). In adjusted models, this difference was not statistically significant. In all models mortality was higher for patients who did not receive vitamin D versus those who did (1.2 (1.1-1.3)). Mortality in doxercalciferol- and paricalcitol-treated patients was virtually identical. Differences in survival between vitamin D2 and D3 may be smaller than previously reported.

Predicting the probability of abortion in dairy cows: a hierarchical Bayesian logistic-survival model using sequential pregnancy data.

Although abortion contributes substantially to poor reproductive health of dairy herds, little is known about the predictability of abortion based on age, previous abortion or gravidity (number of previous pregnancies). A poor understanding of effects of maternal factors on abortion risk exists, in part, because of methodological difficulties related to non-independence of multiple pregnancies of the same cow in analysis of fetal survival data. We prospectively examined sequential pregnancies to investigate relationships between fetal survival and putative dam risk factors for 2991 abortions from 24,706 pregnancies of 13,145 cows in nine California dairy herds. Relative risks and predicted probabilities of abortion (PPA) were estimated using a previously described hierarchical Bayesian logistic-survival model generalized to incorporate longitudinal data of multiple pregnancies from a single cow. The PPA increased with increasing dam age at conception, with increasing number of previous abortions, and if the previous pregnancy was aborted >60 days in gestation. The PPA decreased with increasing gravidity and with increasing number of days open. For cows that aborted, the median time to fetal death decreased slightly as gravidity increased. The study considers several methodological issues faced in epidemiologic investigations of fetal health, including multi-modal hazard functions, extensive censoring and non-independence of multiple pregnancies. The model improves our ability to predict bovine abortion and to characterize fetal survival, which have important applications to herd health management.

Insulin regulation in AhR-null mice: embryonic cardiac enlargement, neonatal macrosomia, and altered insulin regulation and response in pregnant and aging AhR-null females.

The aryl hydrocarbon receptor (AhR) was originally characterized because of its high affinity binding of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin. However, studies using AhR-null mice have demonstrated the importance of this protein in normal physiology and development. Here we demonstrate that AhR-null embryos develop cardiac enlargement, and that this phenotype is dependent, at least in part, on the maternal genotype. Neonates born to AhR-null females had increased heart weights regardless of the neonatal genotype, an outcome also observed in gestational diabetes. The cardiac hypertrophy markers, beta-myosin heavy chain and atrial natriuretic factor, and the cardiac proliferative index were increased in AhR-null embryos, indicating that the cardiac enlargement is associated with myocyte hypertrophy and hyperplasia, which begin prior to birth. Importantly, two- to three-month-old pregnant and seven-month-old nonpregnant females, but not nonpregnant three-month-old AhR-null females had significantly decreased fasting plasma insulin levels and a reduced ability to respond to exogenous insulin compared to controls. Despite these alterations in insulin regulation and responsiveness, pregnant AhR females did not have abnormal glucose tolerance tests and did not develop hyperglycemia, classic characteristics of gestational diabetes. However, twenty-three percent of seven-month-old AhR-null females did have altered glucose tolerance tests, but did not show hyperglycemia or increased hemoglobin A1C concentration under normal feeding conditions. While the ultimate cause of the neonatal phenotype remains unclear, these studies establish that the AhR is required for normal insulin regulation in pregnant and older mice and for cardiac development in embryonic mice.

Mammography utilization after a benign breast biopsy among Hispanic and non-Hispanic women.

BACKGROUND: In spite of the effectiveness of mammography screening for early detection of breast carcinoma, the use of screening mammography varies widely across racial and ethnic groups. Recently, concerns have been raised about the potential adverse effect a benign breast biopsy may have on subsequent mammography utilization, including subsequent use among minority women. METHODS: Computerized health care claims data for 1991 through 1997 from a managed care organization were used to compare mammography use among Hispanic and non-Hispanic women who had had a mammogram followed by an incisional or excisional benign breast biopsy to women who had had a mammogram and no biopsy. Through survival analysis methods, the time-to-next mammogram was compared among these three groups. RESULTS: The sample included 693 (3.2%) and 289 (1.3%) women who had had a mammogram followed by an incisional biopsy or an excisional biopsy, respectively, and 20,540 (95.4%) women who had had a mammogram and no biopsy. Both Hispanic and non-Hispanic women with a biopsy returned sooner for subsequent mammograms than women without a biopsy (P < 0.0001). Hispanic women without a biopsy returned later than non-Hispanic women without a biopsy (P < 0.0001). However, Hispanic women with an excisional biopsy returned sooner than non-Hispanic women (P < 0.05). CONCLUSIONS: Within a managed care organization, both Hispanic and non-Hispanic women who had had a mammogram followed by a benign breast biopsy returned sooner for a subsequent mammogram than women who had had a mammogram and no biopsy. However, ethnic differences in time-to-next mammogram were observed for women without a biopsy and those with an excisional biopsy. Hispanic women without a biopsy returned later for a subsequent mammogram than non-Hispanic women in similar groups, but those with an excisional biopsy returned sooner.

The excess costs of breast cancer health care in Hispanic and non-Hispanic female members of a managed care organization.

The differences in costs for health care services between women with breast cancer and those without were estimated for Hispanic and non-Hispanic members of a managed care organization. A total of 317 cases of breast cancer and 949 controls were selected using a comprehensive patient database. All health care costs for the 4-12 months prior to the case's diagnosis and for the 12 months following the case's diagnosis were obtained. Costs were defined as charges to the health plan. Mean differences in total health care costs between cases and controls were predicted using Tobit models for 4-12 months prior to diagnosis and the year after diagnosis by age group. Compared to controls, women diagnosed with in situ breast cancers in all age groups had significantly higher health care costs 4-12 months prior to diagnosis. For women under 50 years of age, the difference in costs for cases compared to controls 12 months after diagnosis was almost three times greater for women with regional/distant disease ($17,093 +/- $1,559) compared to in situ disease ($5,089 +/- $1,050). For women in the two other age groups (50-70 years and over 70 years), the difference was over twice as great for those with regional/distant disease compared to those with in situ disease. Mean differences between cases and controls in health care costs 12 months after diagnosis were similar for Hispanic and non-Hispanic women for all stages of disease.

Estimating the Mahalanobis distance from mixed continuous and discrete data.

We present a method for estimating the Mahalanobis distance between two multivariate normal populations when a subset of the measurements is observed as ordered categorical responses. Asymptotic properties of the proposed estimator are developed. Two examples are discussed.

Bayesian accelerated failure time analysis with application to veterinary epidemiology.

Standard methods for analysing survival data with covariates rely on asymptotic inferences. Bayesian methods can be performed using simple computations and are applicable for any sample size. We propose a practical method for making prior specifications and discuss a complete Bayesian analysis for parametric accelerated failure time regression models. We emphasize inferences for the survival curve rather than regression coefficients. A key feature of the Bayesian framework is that model comparisons for various choices of baseline distribution are easily handled by the calculation of Bayes factors. Such comparisons between non-nested models are difficult in the frequentist setting. We illustrate diagnostic tools and examine the sensitivity of the Bayesian methods.

ICISS: an international classification of disease-9 based injury severity score.

BACKGROUND: The Injury Severity Score (ISS) has served as the standard summary measure of human trauma for 20 years. Despite its stalwart service, the ISS has two weaknesses: it relies upon the consensus derived severity estimates for each Abbreviated Injury Scale (AIS) injury and considers, at most, only three of an individual patient's injuries, three injuries that often are not even the patient's most severe injuries. Additionally, the ISS requires that all patients have their injuries described in the AIS lexicon, an expensive step that is currently taken only at hospitals with a zealous commitment to trauma care. We hypothesized that a data driven alternative to ISS that used empirically derived injury severities and considered all of an individual patient's injuries would more accurately predict survival. METHODS: Survival risk ratios were derived for every International Classification of Disease 9th Edition (ICD-9) injury category (800-959.9) using the North Carolina State Discharge Database experience with 300,000 trauma patients over 5 years. An ICD-9 Injury Severity Score (ICISS) was then defined as the product of all survival risk ratios for an individual patient's traumatic ICD-9 codes. We compared the performance of ISS and ICISS in a group of 3,142 patients accrued at the University of New Mexico Trauma Center over 4 years. These patients had both AIS and ICD-9 descriptors meticulously assigned prospectively by designated trauma data base personnel. RESULTS: ICISS outperformed ISS at a level that was highly statistically significant (p < 0.0001) and may be clinically important: ISS misclassification rate 7.67%, ISS Receiver Operator Characteristic Curve area = 0.872; ICISS misclassification rate 5.95%, ICISS Receiver Operator Characteristic Curve area = 0.921. Moreover, these improvements are largely preserved when ICISS is used in a probability of survival model that includes age, mechanism, and revised trauma score. About half of ICISS's improvement in predictive power is because of its use of an individual patient's worst three injuries regardless of body region. The remainder is because of better modeling of individual injuries and allowing all injuries to contribute to the final score. CONCLUSIONS: We conclude that ICISS is a much better predictor of survival than ISS in injured patients. The use of the ICD-9 lexicon may avoid the need for AIS coding, and thus may add an economic incentive to the statistical appeal of ICISS. It is possible that a similar data driven revision of ISS using the AIS vocabulary might perform as well or better than ICISS. Indeed, the actual lexicon used to divide up the injury "landscape" into individual injuries may be of little consequence so long as all injuries are considered and empirically derived SRRs are used to calculate the final injury measure.

Assessing the fit of the logistic regression model to individual matched sets of case-control data.

We develop exact conditional methods for checking the fit of a logistic regression model to individual matched sets in case-control studies. Justifications are given for preferring this approach to conventional maximum likelihood-based methods. Data from two studies are used to illustrate the techniques.

An empirical assessment of saddlepoint approximations for testing a logistic regression parameter.

Saddlepoint methods provide quick and easy approximations to significance levels for conditional tests of logistic regression parameters. We evaluate the accuracies of saddlepoint approximations for three well-known conditional tests: Bartlett's test for no three-factor interaction in a 2 x 2 x 2 table, the test for trend in a series of probabilities, and the exact test of no association in stratified 2 x 2 tables with a common odds ratio. General recommendations are suggested regarding the use of saddlepoint approximations for exact conditional significance levels.

A family of confidence intervals for the ratio of two binomial proportions.

The power divergence family of statistics introduced by Cressie and Read (1984, Journal of the Royal Statistical Society, Series B 46, 440-464) is used to obtain approximate confidence intervals for the ratio of two proportions. Intervals based on inverting the Pearson, likelihood-ratio, and Freeman-Tukey statistics are included in this family. Small-sample comparisons of the intervals are presented.