A measurement of the efficacy of nosocomial infection control using the 95 per cent confidence interval for infection rates

From 1981 through 1985, the authors studied the changes in monthly nosocomial infection rates at the University of Virginia Hospital in Charlottesville, Virginia using the 95% confidence interval for infection rates as a marker of the efficacy of infection control activities. For a 99-month baseline period, monthly infection rates were calculated and the 95% confidence interval was established. In the 60 study months, each monthly rate was compared with the 95% confidence interval for that particular month. At the end of each study year, the monthly infection rates were incorporated into the existing confidence interval. Of 60 monthly rates during the study period, 30 were below the confidence interval (p less than 0.00001), two were above the confidence interval (p = 0.23), and 28 were within the confidence interval. Since there was no reduction in surveillance activity, patient case-mix index, or laboratory sensitivity for organism recovery, these results suggest that monthly nosocomial infection rates at this hospital have decreased when compared with the baseline period. The use of the 95% confidence interval may provide a measure of the efficacy of infection control activities, suggest temporal intervals requiring more intensive infection surveillance, and provide a method for examining the variability in monthly infection rates.     

Delta hepatitis virus infection in China

To assess the prevalence, epidemiological features and prognostic implications of hepatitis D (Delta) in Sichuan Province, The People's Republic of China, 649 sera (515 from HBsAg positive patients and 134 from HBsAg negative subjects) were tested by radioimmunoassay (RIA) for antibody to the hepatitis D virus (anti-HD). Forty-seven sera (7.2%) showed some degree of reactivity. Serial dilutions of these sera indicated that prozoning was not responsible for the equivocal results. Thirty-four of the 47 sera were submitted under code to a second laboratory for independent analysis. According to those results anti-HD antibodies were detected in four of these sera. The overall prevalence of anti-HD in the HBsAg positive patients therefore was 0.8% (4/515). On the basis of clinical, biochemical and histological data 427 HBsAg positive sera were further divided into acute Type B hepatitis, chronic Type B hepatitis, healthy carrier state and hepatocellular carcinoma (HCC) subgroups. Two of 65 (3.1%) anti-HD positive sera belonged to the acute Type B hepatitis group; one of 104 (0.9%), the chronic Type B hepatitis group and one of 246 (0.4%), the healthy carrier group. No antibody was detected in sera from 12 HBsAg positive HCC patients. All HBsAg negative patients were negative for anti-HD antibody. The results of this study indicate that despite a high prevalence of hepatitis B virus infection, positive serology for delta virus is uncommon in Sichuan Province, The People's Republic of China.     

Permeation of chemical protective clothing by three binary solvent mixtures

An evaluation of glove materials against three different binary chemical mixtures selected from common industrial solvents was conducted. Changes in breakthrough time and permeation rate of the mixture components were evaluated as a function of the mixture composition. An increase in employee risk resulting from early mixture breakthrough time and enhanced mixture permeation rate over that of the pure chemicals was demonstrated. The permeation of a binary mixture through chemical protective clothing could not be predicted by the permeation results of the pure components. It is recommended that chemical protective clothing be tested for its permeation characteristics with the use of the chemical mixtures and conditions that reflect the work site exposure.     

Exposure to formaldehyde and cancer mortality in a cohort of workers producing resins

The mortality of 1,332 male workers employed at least 30 days in 1959-1980 in a resins-manufacturing plant was examined. Ambient measurements taken in the plant between 1974 and 1979 documented a potential for exposure to levels of formaldehyde as high as greater than 3.0 mg/m3. Vital status was ascertained for 98.6% of the cohort members, and their mortality was compared with expected deaths drawn from the national and local population rates. A statistically significant increase in lung cancer was observed, based on 18 deaths, which was not fully accounted for by possible confounding factors linked to personal habits or sociocultural characteristics. This elevated risk, however, could not be attributed specifically to exposure to formaldehyde. Mortality from digestive cancer (14 deaths observed) and hematologic neoplasms (5 deaths observed) was not substantially higher than expected. The study was limited by information bias due to incomplete work histories, by the small number of deaths from some relevant causes, and by the possibly insufficient length of the observation period. Therefore these results do not provide sufficient grounds either to link formaldehyde exposure in the plant to the increased cancer risk noted or to exclude that formaldehyde might pose such a risk to humans under certain exposure circumstances.     

Calcitonin gene-related peptide: functional role in cerebrovascular regulation.

Distribution studies disclosed that all major cerebral arteries and cortical arterioles of the cat were invested with fine varicose nerve fibers that contained calcitonin gene-related peptide (CGRP)-like immunoreactivity; the trigeminal ganglia likewise contained CGRP immunoreactivity. Sequential immunostaining with antibodies to CGRP and to substance P (SP) revealed identical distributions of these two peptides in trigeminal ganglia and cerebrovascular nerve fibers, suggesting that CGRP and SP are colocalized in these nerves. CGRP completely disappeared from ipsilateral blood vessels after unilateral section of the trigeminal nerve. Exogenous CGRP was a potent relaxant of feline middle cerebral arteries in vitro (maximum relaxation, 10.5 +/- 1.5 mN; concentration eliciting half-maximal response, 9.6 +/- 1.3 nM). Perivascular microapplication of CGRP to individual cortical arterioles of chloralose-anesthetized cats provoked dose-dependent dilatations (maximum increase in diameter, 38 +/- 5%; concentration eliciting half-maximal response, approximately equal to 3 nM). CGRP was significantly more potent than SP as a cerebrovascular dilator, both in vitro and in situ. Chronic division of the ipsilateral trigeminal nerve in cats did not modify the magnitude of arteriolar responses to perivascular microapplication of either vasoconstrictor or vasodilator agents, but the duration of vasoconstrictor responses to norepinephrine (0.1 mM) or alkaline solutions (pH 7.6) was significantly increased. The cerebrovascular trigeminal neuronal system, in which CGRP is the most potent vasoactive constituent, may participate in a reflex or local response to excessive cerebral vasoconstriction that restores normal vascular diameter.