Adult height corrected for shrinking and secular trend.

BACKGROUND: If in growth studies on adults of different ages and generations height standard deviation scores (SDS) is to be calculated, individual heights should be compared with the average height for that generation (corrected for secular trend) at that age (corrected for shrinking). AIM: To generate mathematical formulas for calculating adult height SDS corrected for shrinking and secular trend. SUBJECTS AND METHODS: Decline of height by age was modelled based on data derived from the Baltimore Longitudinal Study of Aging. Based on mean height of Dutch conscripts in 1917 and data from four consecutive nationwide growth studies (1955, 1965, 1980 and 1997), and assuming a constant male-female difference of 13 cm, the secular trend was modelled over 80 years. The average coefficient of variation was calculated from the last three Dutch nationwide growth studies. RESULTS: Height at 21 years of age can be estimated as current height t 0.042*(age - 21) -0.0015*(age - 21)2 for males, and current height + 0.039*(age - 21) + 0.0019*(age - 21)2 for females. Mean height of 21-year-olds between 1917 and 1997 is characterized by linear regression. The coefficient of variation was close to 3.8%. Adult height SDS is calculated by the equation (A - B)/(0.038B), where A is the estimated individual height at 21 years and B is the average height of 21-year-olds in that generation. CONCLUSION: For studies on adult height at various ages and in various generations, these equations can be used to reduce experimental noise.

Semiautomated DNA mutation analysis using a robotic workstation and molecular beacons.

BACKGROUND: Our increasing knowledge of the genetic basis of inheritable diseases requires the development of automated reliable methods for high-throughput analyses. METHODS: We investigated the combination of semiautomated DNA extraction from blood using a robotic workstation, followed by automated mutation detection using highly specific fluorescent DNA probes, so-called molecular beacons, which can discriminate between alleles with as little as one single-base mutation. We designed two molecular beacons, one recognizing the wild-type allele and the other the mutant allele, to determine genotypes in a single reaction. To evaluate this procedure, we examined the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene, which is associated with an increased risk for cardiovascular disease and neural tube defects. DNA was isolated from 10 microL of fresh EDTA-blood samples by use of a robotic workstation. The DNA samples were analyzed using molecular beacons as well as conventional methods. RESULTS: Both methods were compared, and no differences were found between outcomes of genotyping. CONCLUSIONS: The described assay enables robust and automated extraction of DNA and analysis of up to 96 samples (10 microL of blood per sample) within 5 h. This is superior to conventional methods and makes it suitable for high-throughput analyses.

Automated extraction and amplification of DNA from whole blood using a robotic workstation and an integrated thermocycler.

Growing knowledge of the genetic basis of inheritable diseases has resulted in a rapidly increasing demand for DNA mutation analysis. Current methods are reliable and suitable for low-throughput mutation analyses, but are unable to cope with the increasing demand for genetic analyses, necessitating the development of new, fully automated and reliable methods. We developed a semi-automated method for DNA mutation analysis by integrating a thermocycler into a robotic pipetting workstation. DNA was extracted from 84 samples of 10 microl of EDTA-treated whole blood using magnetic beads within 2 h. Directly after isolation, the DNA was automatically transferred to an integrated thermocycler for amplification. Our semi-automated method proved to be reliable and robust, showing unambiguously interpretable PCR signals without occurrence of contamination. It is also faster than conventional manual methods. Only a brief manual intervention is required to remove and refit the seal of the PCR plate. This semi-automated assay is a step forward in the development of fully automated assays for DNA mutation analysis.