Passive smoking in infants, children and adolescents. The effects of diet and socioeconomic factors.

OBJECTIVES: Many studies have associated environmental tobacco smoke (ETS) exposure with an increased risk for various diseases in infants and children, and although superficially the evidence is compelling, on closer scrutiny socioeconomic factors, especially diet, could have a greater contributory effect. An analysis of this evidence was made. RESULTS: Studies which have correlated smoking during pregnancy with low birth weight have considered weight gain and cholesterol levels as a measure of nutrition in the mother, but not the micronutrient content of the diet to which low birth weights could be due. Several authors have attributed ETS exposure to the presence of abnormal lipid profiles in children and adolescents, without considering the diet of the latter, and the abnormal lipids have been linked to a subsequent increased risk for atherosclerosis. The evidence linking lower respiratory infections and bronchitis with passive smoking is strong, although it seems likely that the diet of the mother during pregnancy or breast feeding is equally important. Similarly, increased risks for asthma, otitis media and sudden infant death syndrome have been attributed to the effects of passive smoking, without adequate allowance for confounding by other socioeconomic factors. CONCLUSION: After consideration of the accumulated evidence, it seems improbable that the small exposure could produce all of the effects claimed.

Multicenter evaluation of lyophilized and deep-frozen plasmas for assignment of the International Normalized Ratio.

The interlaboratory variation of the International Normalized Ratio (INR) in various external quality assessment schemes is still relatively high. This is partly caused by inaccuracy of manufacturers' stated International Sensitivity Index (ISI) and/or local instrumentation effects. The interlaboratory variation and accuracy of INR determinations may be improved by a local calibration procedure based on lyophilized plasmas with assigned INRs. The purpose of the present study was to determine INR values for different types of lyophilized plasmas to be used for local calibration. A total of 13 lyophilized plasmas (one normal, six from coumarin-treated patients, six artificially depleted) were analyzed by 10 laboratories, each using five calibrated prothrombin time (PT) systems. INRs were calculated for each plasma using each laboratory's specific ISI and mean normal prothrombin time values. In the same way, five deep-frozen pooled plasmas from coumarin-treated patients were analyzed. There were significant INR differences for the lyophilized plasmas between the prothrombin time systems. The differences were relatively small for the deep-frozen coumarin plasmas (CV 2.6-3.3%) and three lyophilized coumarin plasmas from one manufacturer (CV 3.7-4.8%). Important INR differences were observed for three lyophilized coumarin plasmas from another manufacturer (CV 9.5-14.1%) and several artificially depleted plasmas (CV 5.3-12.8%). The citrate concentrations in the artificially depleted plasmas were lower than those in the normal and coumarin plasmas. These differences should be considered in the selection and certification of plasmas as calibrants for local calibration of PT systems. The lyophilized plasmas' INR values obtained in the present study will be used for a field study of local PT calibration to assess their efficacy.

Influence of three types of automated coagulometers on the international sensitivity index (ISI) of rabbit, human, and recombinant human tissue factor preparations--a multicenter study.

Five tissue factor reagents and three types of automated instruments for prothrombin time (PT) determination were studied in an international multicenter collaborative exercise. The purpose of this work was to determine the international sensitivity index (ISI) for each combination of reagent and instrument against the international reference preparation RBT/90. Each type of instrument was used by 3 or 4 centers to assess the interlaboratory variation of the ISI. The interlaboratory variation of the ISI for each combination of reagent and instrument ranged between 0.4% and 7.8% coefficient of variation. For three reagents, the mean ISI values for ACL (nephelometric) and STA (mechanical) were practically identical, but the mean ISI values for MLA (photo-optical) were at least 10% higher. For two other reagents prepared from rabbit tissue, the mean ISI values increased in the order ACL, STA, MLA. The widest range of mean ISI values was noted with one rabbit tissue factor reagent: 1.68 for ACL and 2.00 for MLA. Exclusion of patient specimens with INR <1.5 and INR >4.5 determined by the international reference preparation resulted in a slight decrease of the mean ISI. The interlaboratory variation of the International Normalized Ratio (INR) was assessed from the results obtained with common lyophilized and deep-frozen plasmas. The use of instrument-specific ISI values resulted in reduced interlaboratory variation of the INR. It is recommended that thromboplastin manufacturers provide instrument-specific ISI values.

An attempt to standardize the APTT for heparin monitoring, using the P.T. ISI/INR system of calibration. Results of a 13 centre study.

Five APTT reagents, a heparin clotting assay and a chromogenic assay have been tested at 13 centres using lyophilised plasma containing different levels of added heparin (in vitro samples), and fresh normal plasma samples and samples from patients receiving heparin therapy (ex vivo samples). Marked differences in sensitivity between the reagents to in vitro and ex vivo samples were found. When calibration of the reagents was attempted using orthogonal regression analysis based on the P.T. ISI/INR system, the results were disappointing. Whichever reagent was accepted as standard, the between laboratory differences in ISI's were very large, and the within laboratory and between laboratory CV's were unacceptably high. Regression lines through normal and patient clotting times were commonly non parallel or skewed. From the results of only 5 out of more than 30 commercial reagents, it is concluded that the application of such a system would give no confidence in any individual result and could be misleading.