Multistate methodology improves risk assessment under time-varying drug intake-a new view on pregnancy outcomes following coumarin exposure.

PURPOSE: Observational cohort studies are essential to evaluate the risk of adverse pregnancy outcomes associated with drug intake. Besides left truncation and competing events, it is crucial to account for the time-dynamic pattern of drug exposure. In fact, potentially harmful medications are often discontinued, which might affect the outcome. Ignoring these challenges may lead to biased estimation of drug-related risks highlighting the need for adequate statistical techniques. METHODS: We reanalyze updated data of a recently published study provided by the German Embryotox pharmacovigilance institute. The aim of the study was to quantify the effect of discontinuation of vitamin K antagonist phenprocoumon on the risk of spontaneous abortion. RESULTS: We outline multistate methodology as a powerful method removing bias in probability estimation inherent to commonly used crude proportions. We incorporate time-dependent discontinuation and competing pregnancy outcomes as separate states in a multistate model, which enables the formulation of hazard-based Cox proportional hazard models and the application of so-called landmark techniques. Results show that early discontinuation of phenprocoumon substantially reduces the risk of spontaneous abortion, which is of great importance for both pregnant women and treating physicians. CONCLUSIONS: An adequate handling of discontinuation times is essential when analyzing the risk of spontaneous abortion. The proposed concepts are not restricted to pregnancy outcome studies but have broad usage in other fields of epidemiology. Our nontechnical report may provide guidance for the design and analysis of future studies. Example code is provided.

Exposure to cox-2 inhibitors (coxibs) during the first trimester and pregnancy outcome: a prospective observational cohort study.

PURPOSE: Cox-2-inhibitors (coxibs) are not recommended in pregnancy but early exposure may occur, for instance in unplanned pregnancies. Experience in pregnancy is limited leading to concerns in patients and their health care providers. Therefore, further data on coxibs and their effects on embryogenesis are needed. METHODS: This observational cohort study evaluates pregnancies ascertained in Germany during the study period from January 2000 to January 2016. A cohort of 174 women exposed to coxibs in the first trimester was compared to a randomly selected cohort of 521 women without exposure to coxibs, other nonsteroidal anti-inflammatory drugs or known teratogens. RESULTS: The overall rate of major birth defects was not significantly increased in the study cohort (2.9 vs. 2.7%, OR 1.08, 95% CI 0.34-3.42; OR adjusted 0.96, 95% CI 0.28-3.26). The cumulative incidence of spontaneous abortions was nonsignificantly lower in the exposed cohort (14.3 vs. 20.0%; HR, 0.90, 95% CI 0.51-1.58; HR adjusted, 0.87; 95% CI, 0.49-1.56). Elective terminations of pregnancies (ETOP), mainly for 'social' reasons, were more frequent in the coxib cohort (17.5 vs. 7.0%, HR, 2.31; 95% CI, 1.26-4.24; HR adjusted 2.12, 95% CI 1.13-3.97). CONCLUSIONS: Our study results support the assumption that coxibs are not major teratogens. Considering the still limited evidence basis on coxib exposure during pregnancy, well-established alternatives should be preferred.

Isotretinoin exposure and pregnancy outcome: an observational study of the Berlin Institute for Clinical Teratology and Drug Risk Assessment in Pregnancy.

OBJECTIVE: Apart from thalidomide, retinoids like isotretinoin are the strongest teratogens in humans known today. The overall risk of birth defects is estimated as up to 30% after exposure during embryogenesis. In spite of well established pregnancy prevention programs, pregnancies still occur during isotretinoin therapy in many countries including Germany. A detailed investigation of the incidence and outcome of these pregnancies would fill an important gap. METHODOLOGY: The Berlin Institute for Clinical Teratology documents prospectively the course of drug-exposed pregnancies when contacted for individual drug risk assessment. Datasets of isotretinoin exposed pregnancies recorded between 1993 and 2008 were evaluated as to the outcome of pregnancy. RESULTS: A total of 108 pregnancies exposed to systemic isotretinoin (median dosage 20 mg/day) during the contraindicated period were registered. 76% (69/91) of the pregnancies with known outcome were electively terminated-mainly for fear of medication risk. No terminations due to abnormal prenatal ultrasound findings were reported. Spontaneous abortions occurred in five pregnancies. Of 18 live births including 1 pair of twins 1 major birth defect (small ventricular septal defect) was observed. None of the infants showed symptoms of retinoid embryopathy. 70% (48/69) of the patients with data on contraception did not use any method, in 30% contraception failed. There was no evidence that poor maternal education was a major cause for the omission of contraception documented in 48 women. CONCLUSION: Inadvertent isotretinoin exposure during the first 2 weeks post conception does not necessarily require discussion of termination of pregnancy, as the risk of major birth defects appears to be much lower than it becomes beyond this period. Nevertheless, additional efforts are required to improve the effectiveness of contraception while on isotretinoin treatment considering psycho-social aspects such as improved self-confidence, unexpected new partnership and sexual activity and incorrect perception of infertility.

GlobalANCOVA: exploration and assessment of gene group effects.

MOTIVATION: Several authors have studied expression in gene sets with specific goals: overrepresentation of interesting genes in functional groups, predictive power for class membership and searches for groups where the constituent genes show coordinated changes in expression under the experimental conditions. The purpose of this article is to follow the third direction. One important aspect is that the gene sets under analysis are known a priori and are not determined from the experimental data at hand. Our goal is to provide a methodology that helps to identify the relevant structural constituents (phenotypical, experimental design, biological component) that determine gene expression in a group. RESULTS: Gene-wise linear models are used to formalize the structural aspects of a study. The full model is contrasted with a reduced model that lacks the relevant design component. A comparison with respect to goodness of fit is made and quantified. An asymptotic test and a permutation test are derived to test the null hypothesis that the reduced model sufficiently explains the observed expression within the gene group of interest. Graphical tools are available to illustrate and interpret the results of the analysis. Examples demonstrate the wide range of application. AVAILABILITY: The R-package GlobalAncova (http://www.bioconductor.org) offers data and functions as well as a vignette to guide the user through specific analysis steps.