Chagas' disease diagnosis: evaluation of several tests in blood bank screening

Blood transfusion is one of the principal routes of transmission of Chagas' disease, a major endemic disease in Latin America. Methods for blood screening are not accurate and may yield false results that lead to high social and economic costs. This study compares two methods of diagnosing Chagas' disease (indirect immunofluorescence and hemagglutination) and several enzyme-linked immunosorbent assays (ELISAs) with regard to specificity and sensitivity, by using human sera with known serologic and parasitologic characteristics, as well as samples with discrepant results on conventional serologic tests. An ELISA using recombinant antigens showed no cross-reactivity with sera that were positive for other diseases. All evaluated ELISAs performed well, and their use may lead to a reduction of more than 50 percent in the number of discordant sera. Further improvements are needed in view of the complexity of the serologic diagnosis of Chagas' disease.     

Predictors of healthy brain aging.

To determine if superior health at old age protects against cognitive impairment (CI) and Alzheimer's disease (AD), we prospectively studied 100 optimally healthy oldest-old (> or =85 years) individuals. Initially, subjects represented the top 3% of the oldest old for health. During 5.6 +/- 0.3 years of follow-up, 34 subjects developed CI, and 23 progressed to AD. By age 100, probability of CI and AD were.65 +/-.09 and.49 +/-.10. Median onset age was 97 years for CI and 100 for AD. Clearly, superior health at old age does not guarantee protection against cognitive decline. Lifetime risks were similar to the general population but onset ages were later, suggesting factors that delay onset are key to improving cognitive health in the elderly. In this population, absence of apolipoprotein E-epsilon4 and male gender were associated with delayed onset, whereas estrogen use and education had no detectable effect on cognitive outcome.     

The role of torovirus in nosocomial viral gastroenteritis at a large tertiary pediatric centre

OBJECTIVE:

To describe the viral etiology and epidemiology of nosocomial viral gastroenteritis (NVG) at a tertiary care pediatric hospital and identify any changes over the past two decades.

METHODS:

Retrospective review of all patients with laboratory-confirmed NVG at The Hospital for Sick Children (Toronto, Ontario), from January 1, 2004, to December 31, 2005.

RESULTS:

One hundred forty-two episodes of NVG were found among 133 patients, occurring in 0.48 of 100 admissions. The median age was two years; 42% were <1 year of age and 41% were immunocompromised. The most commonly detected pathogen was torovirus (67% of episodes), followed by rotavirus (19%) and adenovirus (9%). Seventy-five cases (53%) were epidemiologically linked in 32 separate clusters (median cluster size two, range two to four). The NVG rate fell from 0.63 of 100 to 0.22 of 100 admissions after March 2005 (P<0.001) when enhanced infection control precautions were instituted in response to an outbreak of vancomycin-resistant Enterococcus.

CONCLUSIONS:

Torovirus remains the most commonly identified cause of NVG at The Hospital for Sick Children. Most NVG cases were epidemiologically linked, and a significant reduction in cases occurred after the institution of enhanced infection control practices following an outbreak of vancomycin-resistant Enterococcus. Improved education and surveillance for NVG should lead to further reduction in this problem.     

Beta thalassemia in Melanesia: association with malaria and characterization of a common variant (IVS-1 nt 5 G----C)

Data on the distribution of beta thalassemia among over 6,000 Melanesians reveals a major difference in the carrier rates between populations in the malarious coastal regions of New Guinea and those living in the historically malaria-free Highlands. The island of Maewo in Vanuatu has a particularly high incidence of beta + thalassemia associated with a single restriction enzyme haplotype. Direct cloning into a plasmid vector and sequence analysis demonstrate that the mutation is a G to C transversion at position 5 of intron 1 of the beta- globin gene. Oligonucleotide probe surveys indicate that this variant accounted for all cases of beta thalassemia studied from Maewo. It is also common in coastal Papua New Guinea where haplotype and oligonucleotide probe data suggest that the molecular basis of beta thalassmia is more heterogeneous.     

Partial plasma exchange using albumin replacement: removal and recovery of normal plasma constituents

Using albumin and crystalloid as the only replacement fluids, the effect of partial plasma exchange on the removal and recovery of normal plasma constituents was studied. The results of 30 procedures on 10 individuals were evaluated. Four patterns of removal are described: reduction in the concentration of fibrinogen and C3 were greater than would be expected based upon the extent of the exchange, while IgG, IgM, cholesterol, alkaline phosphatase and SGPT were removed as expected. Reduction of serum glutamicoxalacetic transaminase (SGOT), lactate dehydrogenase (LDH), amylase, and creatine phosphokinase (CPK) averaged 17% less, and uric acid, calcium and K+ averaged 53% less than expected. Concentrations of HCO-3 and glucose did not change. The mean recovery for all constituents except fibrinogen, C3, cholesterol. IgG and IgM was near 100% at 48-72 hr postpheresis. The 72-hr recovery of fibrinogen and complement was 66% and 60%, respectively. Cholesterol recovery was also slow, requiring a minimum of 1 wk to reach prepheresis levels. Measured at a time when quantitative IgM levels were still reduced, alloantibody agglutinating activity (anti-A and anti-B) in a postpheresis sample exceeded prepheresis agglutinating activity. These data demonstrated that, depending upon quantity and frequency of pheresis, partial plasma exchange using albumin replacement may cause progressive marked reduction in concentrations of immunoglobulin, complement, fibrinogen, and cholesterol. Furthermore, newly synthesized antibody may have increased biologic activity.     

Maternal and fetal hepatitis C virus exposure by intrauterine transfusion

We report a case of accidental exposure to hepatitis C virus by an intrauterine transfusion that resulted in infection of the mother but not the child.     

An association between clotting factor concentrates use and mortality in human immunodeficiency virus-infected hemophilic patients

There is much evidence that clotting factor concentrates (CFC), especially the so-called intermediate-purity preparations, exert an immunomodulating effect in vitro. The impact of this effect on the outcome of human immunodeficiency virus (HIV) infection in hemophiliacs is still controversial. In this retrospective cohort study, the effects of treatment with CFC on mortality and progression to acquired immunodeficiency syndrome (AIDS) were estimated while controlling for individual risk factors. Logistic regression and survival analysis, including the Cox proportional-hazards regression model, were performed with data from a 11-year follow-up of 225 hemophilic patients seropositive for HIV type 1 (HIV-1) of two hemophilia centers. Mortality and progression to AIDS rates were strongly associated with lower administration of CFC. After adjusting for age, a statistically significant and robust association was observed. The use of CFC was negatively associated with progression to AIDS (P = .0252) and mortality (P = .0033). The adjusted relative hazards of mortality and progression to AIDS rate between the most treated patients (> 700 IU/kg/yr) versus the least treated (< or = 700 IU/kg/yr) were 0.53 (confidence limits, 0.33 to 0.86) and 0.57 (0.39 to 0.84), respectively. Although the effects of other unmeasured risk factors cannot be excluded with certainty, these results suggest that there is a negative association between treatment with CFC and progression to AIDS and mortality.