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PubMed2001

Adjustment of prognostic effects in prevalent case-control studies on genotype.

Since genotypes are unchangeable, adjustment of prognostic effects in prevalent case-control studies may produce an unbiased estimate of odds ratio (OR) for disease occurrence. In this paper, the prognostic effects on OR is demonstrated, then three approaches to examine and/or adjust the OR are presented. The demonstration shows that the prognostic effects are larger in diseases with poor prognosis than in those with better prognosis. Genotypes increasing disease risk and fatality rate are underestimated, while those increasing the risk and improving prognosis are overestimated. The simplest approach to examine the OR derived from prevalent case-control studies is to conduct stratified analysis according to the interval between diagnosis and study enrollment. When the stratified analysis finds no substantial difference in the estimate, the OR reflects mainly the relative risk for disease occurrence. The proportion of genotype among putative cases at diagnosis can be estimated from prevalent cases by a logistic model, producing the OR adjusted for the interval from diagnosis. An incomplete-data case-control design is also applicable to adjust the prognostic effects. An actual prevalent case-control study on breast cancer is used to demonstrate the three approaches. They are useful to compensate the disadvantage of prevalent case-control studies.

Adult↗

PubMed1997

Stage at diagnosis of prostate cancer in Connecticut by poverty and race.

OBJECTIVE: The study sought to determine if black-white differences in distribution of stage at diagnosis of prostate cancer persisted after controlling for a socioeconomic status (SES) indicator as an ecologic variable. DESIGN: A descriptive epidemiologic study. SETTING: The dataset was from the population-based Connecticut Tumor Registry (CTR), covering patients diagnosed in 1988-92. PARTICIPANTS: All white (N = 8,155) and black (N = 521) patients diagnosed with prostate cancer and reported to the CTR. RESULTS: The proportion of prostate cancers diagnosed at the distant (metastatic) stage was significantly higher in blacks than in whites, even within census tracts with high overall or race-specific poverty rates (20% or higher). When patient age and poverty rate of census tract (deciles) were included in a logistic model, black vs. white race was still statistically significantly associated with diagnosis at the distant vs. local or regional stage. CONCLUSIONS: Further studies are needed to explore the potential roles of black-white differences in screening rates and in biological factors, independent of SES, in explaining these findings.

Black or African American↗

PubMed2005

Psychological symptoms and nonfatal unintentional injuries among Chinese adolescents: a prospective study.

PURPOSE: To describe patterns of nonfatal unintentional injuries and investigate the association of psychological symptoms with injury risk among adolescents in Guangxi, China. METHODS: Adolescents were selected from middle and high school students in Baise City, Guangxi, China. Psychological symptoms at baseline were measured using SCL-90-R and nonfatal unintentional injuries that occurred among participants were recorded using a standardized injury surveillance questionnaire. Annual injury rates per 100 adolescents by adolescents' demographic and family characteristics were calculated. Student's t-test and the Chi-square test were used to test differences in mean raw scores of SCL-90-R subscales and injury rates. Relative risks and odds ratios of injury with 95% confidence intervals were calculated in univariate analyses and multivariate logistic models. RESULTS: A total of 1474 middle and high school students finished the study. Of them, 442 reported nonfatal unintentional injuries during the study period, resulting in an annual injury rate of 30.3 per 100 adolescents. Boys had a significantly higher injury rate than girls (32.6% vs. 27.4%). Injury rate decreased as the adolescents' age increased. Compared with adolescents who were not injured, the injured adolescents had higher average raw scores of all subscales of SCL-90-R, with an exception of the subscale for hostility. All SCL-90-R subscales factors, except those for hostility and phobia, were associated with injury risk. After confounding effects of age, gender, and ethnicity were controlled using logistic regression models, SCL-90-R subscales for somatization (OR = 2.00, 95% CI 1.52-2.63), obsessive-compulsiveness (OR = 2.10, 95% CI 1.71-2.58), interpersonal-sensitivity (OR = 1.66, 95% CI 1.34-2.06), depression (OR = 2.00, 95% CI 1.59-2.51), anxiety (OR = 2.08, 95% CI 1.62-2.66), and psychoticism (OR = 1.60, 95% CI 1.26-2.03) were significantly associated with an elevated injury risk. CONCLUSION: Psychological symptoms are associated with an elevated risk of nonfatal unintentional injury among middle and high school students. Mental health services, such as psychological counseling, may help reduce the risk of nonfatal unintentional injuries among Chinese adolescents.

Accidents↗

PubMed1992

Risk factors which predict pattern of recurrence after curative surgery for patients with advanced gastric cancer.

The objective of the study was to define risk factors for peritoneal dissemination and haematogenous metastasis after curative resection of patients with an advanced gastric cancer. In retrospective analyses of 405 patients, 168 died of a tumour recurrence. Patients who died of gastric cancer were more likely to have large, invasive tumours which had spread throughout the stomach, metastasized to lymph nodes, and vessel invasion by gastric cancerous cells (P < 0.01 or P < 0.05). Of the 168 deaths, 60 (35.7%) were secondary to haematogenous recurrence, 53 (31.5%) were related to peritoneal dissemination, and 19 (11.3%) were related to a local recurrence. To determine the independent risk factors related to peritoneal dissemination and haematogenous metastasis, multivariate analyses using a stepwise logistic model suggested that serosal invasion (P < 0.01, relative risk = 2.57) and Borrmann type 4 (P < 0.01, relative risk = 1.95) were the greatest risk factors for peritoneal dissemination. The presence of lymph node metastasis (P < 0.01, relative risk = 2.62) and presence of vessel invasion by cancerous cells (P < 0.05, relative risk = 1.59) were the greatest risk factors for a haematogenous metastasis.

Cause of Death↗

PubMed1999

Complex segregation analysis for obsessive compulsive disorder and related disorders.

Complex segregation analysis was applied to a sample of 107 Italian families with probands with obsessive compulsive disorder (OCD), using regressive logistic models to test for possible models of genetic transmission. We used two different phenotypic definitions of affection: 1) OCD; and 2) OCD plus Tourette's syndrome/chronic motor tics (CMT). Because of the potential relationship between OCD, Tourette's syndrome (TS), and other tic disorders, we considered these diagnoses to be determined by the same liability in subsequent steps of the analysis. For the 107 OCD families, the best fit was a dominant model of transmission (with a higher penetrance for females). When the phenotype boundaries were widened (OCD + CMT + TS), an unrestricted model of transmission became the best fit. We concluded that additional data are needed to support the hypothesis that Tourette's syndrome and OCD share a common etiology: on the basis of clinical and epidemiological considerations, the OCD phenotype probably presents a higher level of heterogeneity than the TS phenotype, and it could be regulated through different etiologic pathways.

Adolescent↗

PubMed2002

Testing candidate genes for non-syndromic oral clefts using a case-parent trio design.

Markers in five candidate genes were examined on 269 case-parent trios ascertained through a child with an isolated, non-syndromic oral cleft (cleft lip, CL; cleft palate, CP; or cleft lip and palate, CLP). Cases and their parents were ascertained through treatment centers in Maryland. Markers at two of the five candidate genes, transforming growth factor beta3 (TGFbeta3) and MSX1, showed consistent evidence of linkage and disequilibrium due to linkage using several statistical tests (e.g., the global chi-square for TGFbeta3 was 21.1 with 12 df, P = 0.03; that for MSX1 was 8.7 with 3 df, P = 0.03). There was little evidence of heterogeneity in the role of TGFbeta3 between different types of oral clefts, but MSX1 did yield marginal evidence for such heterogeneity. MSX1 also showed evidence for interaction between infant's genotype and maternal smoking, giving a likelihood ratio test for heterogeneity between smoker and non-smoker mothers of 7.16 (2 df, P = 0.03). Using a conditional logistic model to test for gene-gene interaction showed no evidence of interaction between TGFbeta3 and MSX1, with both seeming to contribute independently to risk of isolated, non-syndromic oral clefts.

Adult↗

PubMed2005

Evaluating program effects on institutional delivery in Peru.

We evaluate the joint effects of two targeted Peruvian health programs on a mother's choice of whether to deliver in a public emergency obstetric care (EmOC) facility. The national maternal and child health insurance, or SMI Program, provided delivery care coverage to Peru's poorest households beginning in 1998. During 1996-2002, Proyecto 2000 sought to improve the quality of EmOC and increase utilization of public EmOC facilities in the districts reporting the highest maternal and neonatal mortality levels. Our data come from the Proyecto 2000 endline evaluation, which sampled 5335 mothers living in the catchment areas of 29 treatment and 29 matched control EmOC facilities. Using propensity scoring and two quality of care indices, we find significantly higher quality of care in Proyecto 2000 treatment facilities. Using variance components logistic models, we find a mother enrolled in the SMI Program was more likely to have delivered her last child in a public EmOC, controlling for household constraints. Residence in a Proyecto 2000 treatment area did not significantly affect the choice. A cross-level interaction term was insignificant, indicating the two program effects were independent.

Catchment Area, Health↗

PubMed2001

Laparoscopic cholecystectomy: effective treatment for chronic abdominal pain in children with acalculous biliary pain.

BACKGROUND/PURPOSE: Acalcular biliary pain is a term used to identify patients who have significant abdominal pain related to an abnormally low gallbladder ejection fraction in the absence of cholelithiasis. Little is known about this disease in the pediatric population. The aim of this study was to determine whether laparoscopic cholecystectomy is an effective method for treatment of children with abdominal pain in the setting of acalcular biliary pain and whether one can predict the outcome preoperatively. METHODS: The charts of all children who underwent laparoscopic cholecystectomy for acalcular biliary pain in our institution from January 1991 through April 1998 were reviewed. Sixty-three patients were identified as children with acalcular biliary pain who underwent laparoscopic cholecystectomy. Forty-eight patients were contacted successfully and they all completed the questionnaire. Complete resolution of abdominal pain occurred in 72%, and another 18% had near-complete resolution of pain. Some improvement was noted by 8%, and only 2% had no improvement. In a multiple logistic model, none of the variables were significant predictors of response outcome. CONCLUSIONS: Laparoscopic cholecystectomy is an effective means of therapy for children with abdominal pain and low gallbladder ejection fraction. It is difficult to predict patients with complete response based on the preoperative clinical findings.

Abdominal Pain↗

PubMed1994

The use of logistic discrimination and receiver operating characteristics (ROC) analysis in dentistry.

Logistic regression is a statistical method which allows an investigator to 'explain' or 'predict' a binary response variable from a set of independent variables. In particular, it may be used to classify persons for example, as diseased or healthy, high risk or low risk etc. (logistic discrimination). During recent years this method has been of increasing interest and importance in dentistry. Since this demanding statistical method may not be easily accessible to dentists, a description is provided of its basic characteristics in an introductory and condensed form. A worked example, 'identification of children with high caries risk', is presented in order to demonstrate the application and use of the method. Following the presentation of the logistic model, evaluation of the performance of a classification model by means of 'receiver operating characteristic (ROC) analysis' is demonstrated. The presentation of these statistical tools here, puts more weight on verbal explanation and on graphical representations than on mathematical details. This statistical tools here, puts more weight on verbal explanation and on graphical representations than on mathematical details. This may help to make the methods accessible to readers who have insufficient time to study a more comprehensive discourse.

Child↗

PubMedDate not supplied

Transmission of Plasmodium falciparum in urban Yaoundé, Cameroon, is seasonal and age-dependent.

Data on malaria transmission intensity and prevalences of asexual parasites and of gametocytes were obtained in an urban district of Yaoundé, Cameroon. The transmission level from mosquito to human was determined by indoor night capture of mosquitoes on human volunteers, revealing a calculated entomological inoculation rate of 34 infectious bites per person per year. Only Anopheles gambiae and A. funestus contributed to malaria transmission and their distribution was seasonal. Cross-sectional surveys every 2 months from July 1999 to May 2000 (n = 965) showed average annual prevalences of 35% Plasmodium falciparum asexual parasites (range 29-38%) and 4.4% gametocytes (range 0-6.7%). Prevalence of high parasitaemia (> 400 parasites/microL) and of gametocytes was seasonal. Prevalence of asexual parasitaemias and of gametocytaemias was age-dependent. The potential infectious reservoir in this area is dominated by the age group 0-15 years, representing 75% of carriers of asexual parasites (P < 0.001), 85% of carriers of high parasitaemias (P < 0.001), and 83% of gametocyte carriers (P = 0.03). Full year logistic models developed from the available data accurately predicted parasite prevalences in subsequent analyses, thus permitting a precise determination of study samples for intervention and seroepidemiology studies, and analysis of the infectious reservoir in this area.

Adolescent↗

PubMed2006

Predicting prostate biopsy results: The importance of PSA, age, and race.

We studied whether age and race have a significant role in predicting the results of prostate biopsy after consideration of prostate-specific antigen (PSA) alone. We evaluated the results of 884 prostate biopsies performed on 695 men, including 188 black men. We used logistic regression analysis to evaluate relationships between presence of cancer in the biopsy specimen and the key predictor variables of PSA, age and black race. We also evaluated the importance of a Bayes-derived positive predictive value (PPV), which used age- and race-specific values of specificity and sensitivity of PSA and age- and race-specific Surveillance, Epidemiology, and End Results incidences of prostate cancer. In univariate analysis, the Bayes PPV was associated significantly with presence of cancer (chi2 = 216; P approximately .000); however, serum PSA provided more information (chi2 = 248; P approximately .000). With serum PSA in the logistic model, the Bayes PPV provided no further information (P > .08), and as additional variables, neither age nor black race contributed further information (P > .1). Serum PSA provides the most predictive information about the results of biopsy of the prostate, probably because it naturally correlates with age and race. Decisions about whether to biopsy should rest on values of serum PSA and need not consider age and race.

Age Factors↗

PubMed1995

Recent infection as a risk factor for cerebrovascular ischemia.

BACKGROUND AND PURPOSE: Previous infection is discussed as a risk factor for ischemic stroke in children and younger adults. We tested the hypothesis that the role of recent infection in cerebrovascular ischemia is not restricted to younger patients and investigated which infections are mainly relevant in this respect. METHODS: We performed a case-control study with 197 patients aged 18 to 80 years with acute cerebrovascular ischemia and 197 randomly selected control subjects matched for sex, age, and area of residence. RESULTS: Infection within 1 week before ictus or examination was significantly more common among patients (38 of 197) than control subjects (10 of 197; odds ratio [OR], 4.5; 95% confidence interval [CI], 2.1 to 9.7). Patients more often had febrile and subfebrile infections (> or = 37.5 degrees C) than control subjects (29 of 197 versus 5 of 197; OR, 7.0; 95% CI, 2.5 to 20). Respiratory tract infections were most common in both groups. Bacterial infections dominated among patients but not among control subjects. Infection increased the risk for cerebrovascular ischemia in all age groups; this reached significance for patients aged 51 to 60 and 61 to 70 years. The profile of vascular risk factors was similar in patients with and patients without previous infection. Infection remained a significant risk factor when previous stroke, hypertension, diabetes mellitus, coronary heart disease, and current smoking were included as covariates in a logistic model (OR, 4.6; 95% CI, 1.9 to 11.3). CONCLUSIONS: Recent infection, primarily of bacterial origin, may be a risk factor for cerebrovascular ischemia in older as well as younger patients.

Adolescent↗

PubMedDate not supplied

Early recurrence of hyperthyroidism in patients with Graves' disease treated by subtotal thyroidectomy.

Prerequisites for surgical treatment of Graves' disease are that it can be done safely and that it is associated with a low incidence of recurrent hyperthyroidism. Early recurrence is especially undesirable. We studied 728 patients with Graves' disease treated by subtotal thyroidectomy using multivariate analysis in order to determine the factors related to early recurrence. The following factors were analyzed: age, sex, duration of medical treatment, weight of resected thyroid tissue, thyroid remnant size, preoperative level of thyroid-stimulating hormone (TSH) binding inhibitory immunoglobulin (TBII), and antimicrosomal hemagglutination antibody (MCHA). "Early recurrence" was defined as TSH suppression observed within the first year after surgery and continuing for at least 6 months. A total of 106 patients (14.6%) had early recurrence. Statistical analyses were performed by the chi-square test for univariate analysis and a logistic model for multivariate analysis. Significant factors were thyroid remnant size, MCHA, and TBII. These results indicated that TBII and MCHA are related to early recurrence of hyperthyroidism, and smaller remnant size is recommended for patients with a high MCHA titer or a high TBII level (or both) in order to avoid early recurrence.

Adolescent↗

PubMed1999

Early amniotomy -- high risk factor for cesarean section.

OBJECTIVE: To evaluate the effect of early amniotomy on mode of delivery and pregnancy outcome in comparison to a group of patients admitted with premature rupture of membranes at term. STUDY DESIGN: The study population consists of all women (n=338) whose labor was induced by amniotomy, between the years 1988 to 1995. The comparison group were all women (n=1865) who were admitted with premature rupture of membranes during the same period. RESULTS: Cesarean section was significantly higher in the amniotomy group than in the comparison group (162 (47.9%) vs. 348 (18.7%), P<0.001). This significant difference was noted only for those who did not had a previous cesarean section (106 (42.4%) vs. 224 (13.8%), P<0.001). Non progressive labor during the first stage was threefold higher in the amniotomy group than in the control group (30.8% vs. 10.9%, P<0.001). Abnormal fetal heart rate patterns were detected during labor in 52 patients (15.4%) of amniotomy group, as compared to 141 cases (7.6%) in the control group (P<0.001). To assess the independent contribution of early amniotomy to having cesarean section in the present delivery, a multiple logistic model was used. Early amniotomy (odds ratio [OR] 3.07, 95% confidence interval [CI] 2.36-4.01), as well as a previous cesarean section (OR 5.04, 95% CI 3.90-6.52) and high parity (OR 1.07, 95% CI 1.03-1.26) were all found as independent risk factors for cesarean section. CONCLUSIONS: Early amniotomy appears to be associated with an increased risk for cesarean section.

Adult↗

PubMed2005

Is malarial placental infection related to peripheral infection at any time of pregnancy?

Placental infection measured by placental smear at delivery is a standard indicator, widely used to characterize malaria infection in pregnant women. However, a single measure can hardly reflect the entire history of infection during pregnancy. To investigate the relation between this indicator and peripheral infection during pregnancy, we used data collected in a randomized trial of malaria prophylaxis in 928 pregnant women in Burkina Faso, 1987-1988, during which repeated measures of peripheral infection were taken. We analyzed placental infection using a logistic model, with two methods for handling missing data. Peripheral infection during two periods of pregnancy was significantly related to placental infection at delivery, before the fifth month: OR = 2.9 [1.3; 6.3]; after 7 months: OR = 4.9 [2.7; 8.8]). Therefore, an early peripheral infection may persist throughout gestation, and placental infection is a good indicator of the women's parasitological status during pregnancy.

Adult↗

PubMed2006

Biodegradation kinetics of linear alkylbenzene sulphonates in sea water.

This article reports the primary biodegradation kinetics of linear alkylbenzene sulphonates (LAS) in sea water from the Bay of Cadiz (South West of the Iberian Peninsula). The authors used the biodegradation test guideline proposed by the Office of Prevention, Pesticides, and Toxic Substances of the United States Environmental Protection Agency; 835.3160 "Biodegradability in sea water" in its shake flask variant. High performance liquid chromatography (HPLC) has been employed for the analysis of the surfactant material. The surfactant shows a primary biodegradation kinetic in accordance with a logistic model, the kinetic parameters t (50) and lag time were calculated by means of a easy quantitative procedure introduced. Mean values of 6.15 +/- 0.45 and 6.67 +/- 0.6 days were obtained for t (50) and lag time, respectively. These results indicate that although LAS has a high primary biodegradation rate in sea water, it biodegrades slower than in similar tests conducted in river water.

Alkanesulfonic Acids↗

PubMedDate not supplied

Sampling design, response rates, and analysis weights for the National Human Exposure Assessment Survey (NHEXAS) in EPA region 5.

For the Phase I field test of the National Human Exposure Assessment Survey (NHEXAS) in U.S. Environmental Protection Agency (EPA) Region 5, this paper presents the survey sampling design, the response rates achieved, and the sample weighting procedure implemented to compensate for unit nonresponse. To enable statistically defensible inferences to the entire region, a sample of about 250 members of the household population in EPA Region 5 was selected using a stratified multistage probability-based survey sampling design. Sample selection proceeded in four nested stages: (1) sample counties; (2) area segments based on Census blocks within sample counties; (3) housing units (HUs) within sample segments; and (4) individual participants within sample households. Each fourth-stage sample member was asked to participate in 6 days of exposure monitoring. A subsample of participants was asked to participate in two rounds of longitudinal follow-up data collection. Approximately 70% of all sample households participated in household screening interviews in which rosters of household members were developed. Over 70% of the sample subjects selected from these households completed the Baseline Questionnaire regarding their demographic characteristics and potential for exposures. And, over 75% of these sample members went on to complete at least the core environmental monitoring, including personal exposures to volatile organic compounds (VOCs) and tap water concentrations of metals. The sample weighting procedures used the data collected in the screening interviews for all household members to fit logistic models for nonresponse in the later phases of the study. Moreover, the statistical analysis weights were poststratified to 1994 State population projections obtained from the Bureau of the Census to ensure consistency with other statistics for the Region.

Adolescent↗

PubMed1999

Large volume leukapheresis for collecting hemopoietic progenitors: role of CD 34+ precount in predicting successful collection.

In this work we evaluated the efficacy of stem cell collection with Large Volume Procedures. (LVP), and analysed the importance of the CD34+ cell precount in promoting the collection of a sufficient number of CD34+ cells for transplantation, using the Univariate Logistic Regression analysis. Eighty-nine leukapheresis were performed in 49 patients with hematological malignancies and solid tumors, mobilized with chemotherapy plus Granulocyte Colony Stimulating Factor (G-CSF). For each procedure 15.8 liters of blood were processed. The median value of Nucleated Cells (NC) and CD34+ cells precount was respectively 8.29 x 10(9)/ml (range 1.13/45.4) and 43.08 x 103/ml (range 1.06/795.2). Results show the capability of LVP to collect large quantities of hemopoietic progenitors with a median CD34+ cell total yield of 215.02 x 10(6) (range 5.03/2210). The yields per patients' body weight were: CD34+ cells 3.23 x 10(6)/kg (range 0.081/41.58). The regression analysis between blood cell precounts and collection yields gave the following correlations: the CD34+ cell precount correlates with CD34+ yield (r = 0.78 p < 0.00) and with CD34+ cell yield/kg (r = 0.76 p < 0.00). The number of CD34+ cells processed correlated with the number of CD34+ cells collected/kg (r = 0.83 p < 0.000). To investigate the importance of CD 34+ cell precount in promoting CD34+ cell yields > or =2.5 x 10(6)/kg we performed a Univariate Logistic Regression analysis that showed in our patients a probability of collecting > or =2.5 x 10(6) CD34+/kg that rose from 0.6 to 0.95 for CD 34+ precounts that oscillated from 30 to 40 x 10(3) CD34+ cells/ml, respectively. The Univariate Logistic Regression gave a probability of collecting > or =2.5 x 10(6) CD34+ cells/kg that oscillated between 0.64/0.98 for values of CD34+ cells processed from 6 x 10(6)/kg to 8 x 10(6)/kg, p < 0.000. Sixty-three percent of patients reached the target dose of 2.5 x 10(6) CD34+ cells/kg with only one LVP. Until now 12 patients have been transplanted and all have had a prompt and complete lasting recovery. These results confirm the efficacy of LVP in harvesting hemopoietic progenitors and their ability in reconstituting hemopoiesis of transplanted patients, enabling the estimation of CD34+ precounts and CD34+ cells processed values, highly predictive for the collection of > or =2.5 x 10(6) CD34+ cells/kg. Furthermore, the Logistic Model suggests that the best strategy to plan a successful CD34+ cell collection procedure is to identify for each patient the amount of CD34+ cells/kg to be processed rather than the fixed processing of 3/5 blood volumes in all patients.

Adolescent↗