Pulsatile tinnitus from a redundant arterial loop.
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Adult↗
Biomedical subjects
Alan Johnson
Publications and source records attributed to Alan Johnson.
Outpatient consumption of antibiotics is linked to antibiotic resistance in Europe: results from the European Surveillance of Antimicrobial Consumption.
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Anti-Bacterial Agents↗
A matched-cohort study of selected clinical and utilization outcomes for an asthma care support program.
Estimating the economic and clinical impact of asthma disease management programs traditionally has relied on non-experimental designs and employed matching or stratification methods with limited success. Selecting similar comparison subjects is problematic since subjects must be compared across numerous pretreatment factors. In cases where treatment and comparison subjects differ greatly on observed characteristics, conclusions may be particularly sensitive to an incorrectly specified model used for matching. A propensity score method constructs matched samples of treated-control pairs, addresses program selection bias, and reduces bias in estimates of treatment effects. To investigate the program effects of an asthma care support program delivered to high-risk asthmatics (persons with a previous inpatient admission, emergency department [ED] visit, or observation visit), we conducted a matched-cohort study on 196 participants. Using administrative claims data and selected clinical indicators, we analyzed hospitalization, ED, and physician office visit rates to estimate effects of program enrollment. Total hospitalizations, asthma-related hospitalizations, bed days, and ED visits for participants were lower and statistically different from that of the matched-cohort group during the program period, suggesting the beneficial effects of monitoring, education, and counseling activities for participants. Where controlled randomized clinical trials cannot be performed because of ethical, cost, or feasibility issues, the use of propensity scores provides an alternative for estimating treatment effects using observational data. This study employs a propensity score-matching methodology to select a subset of comparison units most comparable to treatment units, and documents the beneficial outcomes of participation in an asthma care support program.
Adolescent↗
The relationship between nucleoside triphosphate hydrolase (NTPase) isoform and Toxoplasma strain virulence in rat and human toxoplasmosis.
Avirulent strains of Toxoplasma gondii possess only the nucleoside triphosphate hydrolase II (NTPaseII) isoform, whilst virulent strains possess both NTPaseI and NTPaseII. To determine if it is possible to identify the infective strain type (virulent or avirulent) in T. gondii infections by serological methods, we developed isoform-specific peptide ELISAs from the NTPaseI and NTPaseII antigens of T. gondii. When rats were immunized with either recombinant NTPaseI or NTPaseII, the ELISA could differentially identify antibody reactivity to each NTPase isoform. This ELISA was then used to test six groups of rats that were infected with either one of three virulent (RH, P or Ent) or three avirulent (Me49, C or TPR) strains of T. gondii. No differential antibody reactivity was detected by either whole recNTPase ELISA or peptide ELISA in the sera of rats, whether infected by virulent or avirulent strains of T. gondii. We also studied a panel of human sera from patients infected with known laboratory strains of T. gondii or naturally infected patients where the parasite was isolated and its virulence determined in mice. Differential reactivity to whole recNTPase isoforms was detected in some human sera, but this reactivity was not detected by the isoform-specific peptide ELISAs. Although the NTPase peptides do exhibit differential antibody reactivity, this is not correlated with the virulence status of the infecting strain.
Acid Anhydride Hydrolases↗
Tonsillectomy and variant Creutzfeldt-Jakob disease.
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Creutzfeldt-Jakob Syndrome↗
Relationship between mammographic breast density and tamoxifen in women with breast cancer.
Previous studies have reported that tamoxifen use is associated with a decrease in mammographic breast density. This is a potentially valuable finding since mammographic sensitivity is limited by breast density. Anything that reduces breast density would theoretically enhance the sensitivity of mammography for the detection of breast cancer in women at an earlier stage when it is more curable. We performed a retrospective study investigating the potential effect of tamoxifen on breast density. The data for this retrospective study were collected from the records of 52 charts from a single medical oncologist. Patients with breast cancer were selected regardless of stage or age at the time of diagnosis or treatment, as long as their charts had records of bilateral mammograms. For each breast on each woman, both mediolateral oblique and craniocaudal views were reviewed independently by two radiologists on two separate occasions to obtain inter- and intraobserver variability. Two methods of classifying breast density were used: the Breast Imaging Reporting and Data System (BI-RADS), and measurements of percent density. Only age and menopausal status were found to be associated with breast density. There was no correlation between breast density and tamoxifen use (past or present). Our study shows no association between tamoxifen use and breast density. We confirm previous observations that breast density is inversely correlated with age and postmenopausal status.
Adult↗