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A limited sampling method to estimate methotrexate pharmacokinetics in patients with rheumatoid arthritis using a Bayesian approach and the population data modeling program P-PHARM.

This paper describes a methodology to calculate methotrexate (MTX) pharmacokinetic parameters after intramuscular administration using two samples and the population parameters. Total and free MTX were measured over a 36-h period in 56 rheumatoid arthritis patients; 14 patients were studied after a two-dose scheme at 15-day intervals. The Hill equation was used to relate the free MTX to the total MTX changes in plasma concentrations, and a two-compartment open model was used to fit the total MTX plasma concentrations. A non-linear mixed effect procedure was used to estimate the population parameters and to explore the interindividual variability in relation to the following covariables: age, weight, height, haemoglobin, erythrocyte sedimentation rate, platelet count, creatinine clearance, rheumatoid factor, C-reactive protein, swelling joint count, and Ritchie's articular index. Population parameters were evaluated for 40 patients using a three-step approach. The population average parameters and the interindividual variabilities expressed as coefficients of variation (CV%) were: CL, 6.94 l center dot h-1 (20.5%); V, 34.8 l (32.2%); k12, 0.0838 h-1 (47.7%); k21, 0.0769 h-1 (61.6%); ka, 4.31 h-1 (58%); Emax, 1.12 mu mol center dot l-1 (19.7%); gamma, 0.932 (12.3%); and EC50, 2.14 mu mol center dot l-1 (27.3%). Thirty additional data sets (16 new patients and 14 patients of the previous population but treated on a separate occasion) were used to evaluate the predictive performance of the population parameters. Twelve blood samples were collected from each individual in order to calculate individual parameters using standard fitting procedures. These values were compared to the ones estimated using a Bayesian approach with population parameters as a priori information together with two samples, selected from the individual observations. The results show that the bias was not statistically different from zero and the precision of these parameters was excellent.

Adult↗

Childhood cancer patients' access to cooperative group cancer programs: a population-based study.

BACKGROUND: The Children's Oncology Group (COG), a merger of the Children's Cancer Group (CCG) and the Pediatric Oncology Group (POG), conducts clinical trials for the treatment of childhood cancer. To assess the feasibility of developing a nationwide childhood cancer registry, the authors attempted to determine whether COG could serve as a resource for identifying all children with cancer. METHODS: A consolidated file of children age < 20 years who were diagnosed with cancer between 1992-1997 and registered with either CCG or POG was linked with records from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program. Age-specific registration rates and age-adjusted registration rates (AARR) were calculated overall and by year of diagnosis, gender, race/ethnicity, stage of disease at diagnosis, and type of cancer. RESULTS: Of 10,108 children age < 20 years with cancer who were identified by the 11 SEER registries between 1992-1997, 5796 were registered with CCG or POG. The AARR was 71% for children age < 15 years, 24% for adolescents ages 15-19 years, and 57% for children age < 20 years. Registration rates were stable over the years studied, varied by geographic region, and were found to be higher among children with more advanced disease. Registration rates were highest for children with leukemia, hepatic tumors, and renal tumors, and were lowest for carcinoma and retinoblastoma. CONCLUSIONS: The results of the current study demonstrate that not all children with cancer are registered by the cooperative groups; however, a national registry program can be achieved by supplementing cases identified through COG with data collected by statewide population-based cancer registries. Such a partnership would be mutually beneficial, allowing COG to achieve 100% registration of children with cancer and, for the statewide cancer registries, improving the timeliness of case-finding and follow-up information for cancer outcomes.

Child↗

Building culturally sensitive substance use prevention and treatment programs for transgendered populations.

Studies show that transgendered individuals are at high risk for substance use problems. It is important to identify the unique needs and concerns of these individuals and culturally sensitive programs that will be successful in recruiting and retaining these individuals in drug abuse treatment services. This involves incorporating the needs of services from the perspectives of both the transgendered community and health-care professionals. It is the purpose of this article to discuss transgenderism as well as the substance use problems and difficulties within substance use treatment that transgendered men and women may face. This article presents guidelines for the design and evaluation of health-care services to transgendered populations.

Adolescent↗

Down syndrome prevention program in a population with an older maternal age.

OBJECTIVE: To investigate the effect of a relatively high proportion of pregnant women 35 years and older on the efficacy of prenatal screening for Down syndrome. METHODS: We obtained information on normal and abnormal cytogenetic and maternal serum marker studies for 1990 and 1992 from all 11 public and two private cytogenetic laboratories operating in Israel. RESULTS: In the Jewish Israeli population, 16.2-17.1% of all pregnant women are at least 35 years old. Thus, prenatal testing of all pregnant women at least 35 years old could have identified 62.8-66.5% of all Down syndrome cases. Screening by maternal serum markers would classify 9.28% of pregnancies as being at high risk for Down syndrome (greater than 1:386 at birth). The percentage of Down syndrome cases detected prenatally increased from 78 of 147 (53%) to 123 of 163 (75%) as a result of the increased use of prenatal testing from 11.3% to 19.4% of all pregnancies in 1990 and 1992, respectively. CONCLUSIONS: In a population with a high proportion of mothers at least 35 years old, as in the Jewish population in Israel, screening by maternal serum markers instead of by maternal age alone would leave the Down syndrome detection rate unchanged, but would lower the amniocentesis rate from 16.2-17.1% to 9.28%. In addition to the reduction in the expected fetal loss as a result of post-amniocentesis spontaneous abortion, this policy would also pay the cost of maternal serum marker testing of the entire pregnant population.

Adult↗

The prevalence and correlates of Rose Questionnaire angina among women and men in the Lipid Research Clinics Program Prevalence Study population.

The prevalence and correlates of Rose Questionnaire angina were investigated in a sample of 4,661 white woman and men aged 30 years and above who participated in the Lipid Research Clinics Program Prevalence Study 1972-1976. Among men, the prevalence of Rose angina increased with age from about 1% to 12%, while the prevalence among women ranged from about 3% to 6%. Young women compared with men also had a relatively high prevalence of dyspnea, which was strongly correlated with Rose angina in both sexes. For women and men younger than 50 years, the dyspnea-Rose angina odds ratio was about 6 (p less than 0.001), while older women and men had somewhat lower sand higher odds ratios, respectively. Major and minor resting electrocardiographic abnormalities and self-reported history of a heart attack were not significantly associated with Rose angina among young participants of either sex, but they did show positive associations among older participants with the exception of minor electrocardiographic abnormalities in men. A logistic regression analysis revealed a strong inverse association between high density lipoprotein cholesterol and Rose angina in both sexes. Because mortality studies consistently show an excess of coronary heart disease death among young men compared with women, the female excess of Rose angina at young ages suggests that the grouping of angina and myocardial infarction into a single endpoint in cardiovascular disease studies may be more appropriate for young men than for young women.

Adult↗

Determination of robust ocular pharmacokinetic parameters in serum and vitreous humor of albino rabbits following systemic administration of ciprofloxacin from sparse data sets by using IT2S, a population pharmacokinetic modeling program.

Robust determination of the concentration-time profile of anti-infective agents in certain specialized compartments is often limited by the inability to obtain more than a single sample from such a site in any one subject. Vitreous humor and cerebrospinal fluid are obvious examples for which the determination of concentrations of anti-infective agents is limited. Advances in pharmacodynamics have pointed out the importance of understanding the profiles of drugs in the plasma and in specialized compartments in order to dose the drugs to obtain the best patient outcomes. Advances in population pharmacokinetic modeling hold the promise of allowing proper estimation of drug penetration into the vitreous (or other specialized compartment) with only a single vitreous sample, in conjunction with plasma sampling. We have developed a rabbit model which allows multiple samples of vitreous to be obtained without breaking down the blood-vitreous barrier. We have employed this model to test the hypothesis that robust estimates of vitreous penetration by the fluoroquinolone ciprofloxacin can be obtained from a traditional intensive plasma sampling set plus a single vitreous sample. We studied 33 rabbits which were receiving 40 mg of ciprofloxacin per kg of body weight intravenously as short infusions and from which multiple plasma and vitreous samples were obtained and assayed for ciprofloxacin content by high-performance liquid chromatography. Data were analyzed by the iterative two-stage population modeling technique (IT2S), employing the iterative two-stage program of Forrest et al. (Antimicrob. Agents Chemother. 37:1065-1072, 1993). Two data sets were analyzed: all plasma and vitreous samples versus all plasma samples and the initially obtained single vitreous sample. The pharmacokinetic parameter values identified were used to calculate the percent vitreous penetration as the ratio of the area under the concentration-time curve for the vitreous to that for the plasma. The values identified, 4% penetration for the full data set versus 3% penetration for the single vitreous sample data set, and their corresponding estimates were not statistically significantly different. We conclude that population modeling holds promise for the analysis of penetration of antimicrobiol agents into specialized spaces from which only single samples can be obtained, particularly for patients with whom robust plasma sampling can be performed.

Animals↗