CHICAGO—Parents with a child requiring stem cell transplantation can have genetic testing done on embryos prior to implantation to determine if the tissue type matches and the ensuing offspring could potentially serve as a donor to the affected child, according to a study in the May 5 issue of the Journal of the American Medical Association (JAMA).

Preimplantation genetic diagnosis (PGD) has become available as an alternative to prenatal diagnosis in order to avoid the risk for pregnancy termination, because PGD allows selection of unaffected embryos before a pregnancy is established, according to background information. Despite the need for ovarian stimulation and in vitro fertilization (IVF) to be part of the procedure, PGD has become an acceptable method for avoiding the birth of children with genetic disorders.

Preimplantation genetic diagnosis is applicable to indications beyond those of prenatal diagnosis, such as Human Leukocyte Antigen (HLA) matching to affected siblings to provide stem cell transplantation. HLA testing, also known as tissue typing, determines the compatibility between donors and recipients for the transplantation of solid organs (i.e. heart, liver, kidney and lung) and bone marrow. Compatibility within the HLA minimizes immune rejection.

Yury Verlinsky, Ph.D., of the Reproductive Genetics Institute, Chicago, and colleagues report the first clinical experience of preimplantation HLA matching not involving identification of a causative gene to demonstrate the feasibility of this approach for stem cell transplantation in siblings with bone marrow failure.

The study consisted of HLA matching procedures conducted during 2002-2003 in an in vitro fertilization program for nine couples with children affected by acute lymphoid leukemia, acute myeloid leukemia, or Diamond-Blackfan anemia (DBA) requiring HLA-matched stem cell transplantation. DNA was removed from embryos following in vitro fertilization and analyzed for HLA genes, and embryos were transferred that were HLA matched to affected siblings.

The researchers found that as a result of testing of a total of 199 embryos, 45 (23 percent) HLA-matched embryos were selected, of which 28 were transferred in 12 clinical cycles, resulting in 5 singleton pregnancies and birth of 5 HLA-matched healthy children.

CHICAGO—A new study shows that the prevalence of marijuana use among U.S. adults has remained stable over the past decade, but the prevalence of marijuana abuse or dependence has increased significantly, possibly related to increased potency of the substance, according to a report in the May 5 issue of the Journal of the American Medical Association (JAMA).

Marijuana has been the most common illicit substance used in the United States for several decades, and among illicit substance use disorders, marijuana use disorders are the most prevalent in the population, according to background information in the article. Marijuana use is associated with impaired educational attainment, reduced workplace productivity, and increased risk of use of other substances. Marijuana use plays a major role in motor vehicle crashes and has adverse effects on the respiratory and cardiovascular systems. Despite the seriousness of marijuana abuse and dependence, no long-term trend information has been available.

Wilson M. Compton, M.D., M.P.E., from the National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Bethesda, Md., and colleagues assessed changes in marijuana use, abuse, and dependence in the U.S. population. The study consisted of face-to-face interviews conducted in 2 large national surveys conducted 10 years apart: the 1991-1992 National Longitudinal Alcohol Epidemiologic Survey ([NLAES] n=42,862) and the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions ([NESARC] n = 43,093).

Among the U.S. adult population, the prevalence of marijuana use remained stable at about 4 percent over the past decade, while the prevalence of marijuana dependence or abuse significantly increased between 1991-1992 (1.2 percent) and 2001-2002 (1.5 percent). The greatest increases were among young black men and women and young Hispanic men. Marijuana use disorders among marijuana users increased in the absence of increased frequency and quantity of marijuana use. The authors speculate that these findings may be attributable, in part, to increased potency of marijuana.

CHICAGO—Blood pressure among children and adolescents has increased over the past decade, with part of the increase related to an increased prevalence of overweight, according to a study in the May 5 issue of the Journal of the American Medical Association (JAMA).

According to background information in the article, a previous study recently reported that the prevalence of overweight has increased from 11.3 percent to 15.5 percent for adolescent boys and 9.7 percent to 15.5 percent among adolescent girls between 1988-1994 and 1999-2000. The change in blood pressure among children and adolescents over that time and the role of overweight has been unknown.

Paul Muntner, Ph.D., of Tulane University, New Orleans, and colleagues examined data, including systolic and diastolic blood pressure levels, from two studies that used nationally representative samples of children and adolescents, aged 8 to 17 years. They were the third National Health and Nutrition Examination Survey (NHANES III) conducted in 1988-1994 (n = 3,496) and NHANES 1999-2000 (n = 2,086).

The researchers found that between the NHANES III and NHANES 1999-2000 surveys, systolic blood pressure levels increased an average of 1.4 mm Hg and diastolic blood pressure levels increased 3.3 mm Hg. "Significant increases in blood pressure levels were observed in all subgroups for diastolic blood pressure and in most subgroups for systolic blood pressure (non-Hispanic blacks, Mexican-Americans, boys, girls, and those aged 8 through 12 years)," the authors write.

"The increase in body mass index (BMI) during this same period accounted for some of the increase in blood pressure. Given the relationship between BMI and blood pressure and the high and unabated increase in the prevalence of overweight in the United States, the incidence of hypertension is likely to increase. Additionally, factors other than the increase in overweight among children and adolescents appear to have contributed to the increase in blood pressure over the previous decade. Confirmation of the trends observed in the current study is needed. Factors that have resulted in higher blood pressure levels among children and adolescents in the United States also need to be identified.

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