P S McInturff | PubMed Health

PubMed2005

Effect of diagnostic testing error on intracluster correlation coefficient estimation.

Estimation of the intracluster correlation coefficient (ICC) for infectious animal diseases may be of interest for survey planning and for calculating variance inflation factors for estimators of prevalence. Typically, diagnostic tests with imperfect sensitivity and specificity are used in surveys. In such studies, where animals from multiple herds are tested, the ICC often is estimated using apparent (test-based) rather than true prevalence data. Through Monte Carlo simulation, we examined the effect of substituting diagnostic test outcomes for true infection status on an ANOVA estimator of ICC, which was designed for use with true infection status data. We considered effects of diagnostic test sensitivity and specificity on the estimated ICC when the true ICC value and infection status of the sampled individuals were known. The ANOVA estimator underestimated the true ICC when the diagnostic test was imperfect. We also demonstrated, under the beta-binomial model, that the ICC based on apparent infection status for individuals is < or = ICC based on true infection status. In addition, we propose a Bayesian model for estimating the ICC that incorporates imperfect sensitivity and specificity and illustrate the Bayesian model using a simulation study and one example; a seroprevalence survey of ovine progressive pneumonia in U.S. sheep flocks.

Animals↗

PubMed2000

Bovine respiratory syncytial virus-specific IgE is associated with interleukin-2 and -4, and interferon-gamma expression in pulmonary lymph of experimentally infected calves.

OBJECTIVE: To study the local immune response of calves to bovine respiratory syncytial virus (BRSV) infection with emphasis on IgE production and cytokine gene expression in pulmonary lymph. ANIMALS: Twelve 6- to 8-week-old Holstein bull calves. Six similar control calves were mock infected to obtain control data. PROCEDURE: Lymphatic cannulation surgery was performed on 12 calves to create a long-term thoracic lymph fistula draining to the exterior. Cannulated calves were exposed to virulent BRSV by aerosol. Lymph fluid collected daily was assayed for BRSV and isotype-specific IgE antibody, total IgG, IgA, IgM, and protein concentrations. Interleukin-4 (IL-4), interleukin-2 (IL-2), and interferon-gamma were semi-quantitated by reverse transcription-polymerase chain reaction (RT-PCR). Cell counts and fluorescence-activated cell scanner (FACSCAN) analysis of T-cell subsets were performed on lymph cells. RESULTS: Calves had clinical signs of respiratory tract disease during days 5 to 10 after infection and shed virus. Bovine respiratory syncytial virus-specific IgE in infected calves was significantly increased over baseline on day 9 after infection. Mean virus-specific IgE concentrations strongly correlated with increases in severity of clinical disease (r = 0.903). Expression of IL-2, IL-4, and interferon-gamma was variably present in infected and control calves, with IL-4 expression most consistent during early infection. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with BRSV was associated with production of BRSV-specific IgE, and IL-4 message was commonly found in lymph cells of infected calves. This finding supports the concept that BRSV-induced pathophysiology involves a T helper cell type-2 response. Effective therapeutic and prophylactic strategies could, therefore, be developed using immunomodulation to shift the immune response more toward a T helper cell type-1 response.

Animals↗