Adapting the International System of Units to the twenty-first century.

We review the proposal of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM), currently being considered by the General Conference on Weights and Measures (Conférences Générales des Poids et Mesures, CGPM), to revise the International System of Units (Le Système International d'Unitès, SI). The proposal includes new definitions for four of the seven base units of the SI, and a new form of words to present the definitions of all the units. The objective of the proposed changes is to adopt definitions referenced to constants of nature, taken in the widest sense, so that the definitions may be based on what are believed to be true invariants. In particular, whereas in the current SI the kilogram, ampere, kelvin and mole are linked to exact numerical values of the mass of the international prototype of the kilogram, the magnetic constant (permeability of vacuum), the triple-point temperature of water and the molar mass of carbon-12, respectively, in the new SI these units are linked to exact numerical values of the Planck constant, the elementary charge, the Boltzmann constant and the Avogadro constant, respectively. The new wording used expresses the definitions in a simple and unambiguous manner without the need for the distinction between base and derived units. The importance of relations among the fundamental constants to the definitions, and the importance of establishing a mise en pratique for the realization of each definition, are also discussed.

Immunization histories given by adult caregivers accompanying children 3-36 months to the emergency department: are their histories valid for the Haemophilus influenzae B and pneumococcal vaccines?

OBJECTIVE: To obtain immunization histories from adult caregivers accompanying children to the emergency department (ED), to determine the accuracy of the caregiver's report for the Haemophilus influenzae B (Hib)and 7-valent pneumococcal vaccine (PCV7). METHODS: This was a prospective, observational study of children age 3 to 36 months presenting to the Albert Einstein Medical Center ED during the period of November 1, 2004, through January 31, 2005. Caregivers were asked to complete a questionnaire about their child's immunization status and if the child's vaccinations were up-to-date. Immunization records were obtained from the child's most recent primary care physician (PCP) to determine whether the caregiver's report was correct for PCV7 and Hib. Children were considered delayed if they were more than 30 days past due date for one or both vaccines according to the PCP records. RESULTS: Of 205 PCP offices contacted, we were able to obtain 173 immunization records for our analysis. Examination of vaccine records showed that 109 (63.0%) of the 173 children were up-to-date on both immunizations. When the child's caregiver was asked if shots were up-to-date, 159 (91.9%) of 173 said that all shots were given, and only 14 (8.1%) of 173 reported being behind schedule. Of the adults reporting the child up to date, 105 (66.0%) of the 159 children were confirmed to be up-to-date. Thus, 34.0% of caregivers were incorrect in stating that their child's immunization status was up-to-date for both these vaccines. CONCLUSIONS: Caregiver report was determined to be inaccurate for Hib and PCV7. Despite 91.5% of caregivers stating that shots were up-to-date, only 66.0% were correct that their child was up-to-date with these 2 vaccines. The ED physician should use caution in making clinical decisions based on the history given by a caregiver regarding their child's immunization status.