Biomedical subjects

Clément Dassa

Publications and source records attributed to Clément Dassa.

5 recordsLinked to original sources

PubMed2006

Intra- and interobserver agreement and statistical clustering of placental histopathologic features relevant to preterm birth.

OBJECTIVE: Many previous studies of agreement in identifying placental histopathologic lesions have been based on small sample sizes, and none has examined whether individual histologic features cluster robustly together within and between observers. STUDY DESIGN: We studied 767 placental specimens from case-control studies of preterm birth and preeclampsia nested within a prospective cohort of pregnant women recruited from 4 large Montreal maternity hospitals. The specimens were fixed, embedded, stained, and examined using a standardized protocol; a 10% random sample (n = 81) was then blindly reexamined at least 6 months later by the same pathologist and a second pathologist. RESULTS: Intra- and interobserver agreement were high (kappa > or = 0.50) for membrane inflammation, funisitis, and umbilical cord vasculitis, and these 3 features were robustly clustered statistically, consistent with an underlying mechanism of ascending infection. Agreement and clustering were also high or moderate for features of placental underperfusion: infarction, decidual vasculopathy, and syncytial knotting. CONCLUSION: Our results should help researchers to interpret future findings relating placental histopathology to preterm birth, preeclampsia, and other adverse pregnancy outcomes, and to their etiologic determinants and causal pathways.

Case-Control Studies↗

PubMed2006

Understanding place and health: a heuristic for using administrative data.

The increasing availability, use and limitations of administrative data for place-based population health research, and a lack of theory development, created the context for the current paper. We developed a heuristic to interrogate administrative data sets and to help us develop explanatory pathways for linking place and health. Guided by a worked example, we argue that some items in administrative data sets lend themselves to multiple theories, creating problems of inference owing to the implications of using inductive versus deductive reasoning during the research process, and that certain types of theories are privileged when used administrative data bases.

Canada↗

PubMed2003

Ventilator-associated pneumonia in intubated children: comparison of different diagnostic methods.

OBJECTIVES: To compare different methods for diagnosis of ventilator-associated pneumonia in intubated children. DESIGN: Prospective epidemiologic study. SETTING: Pediatric intensive care unit of a tertiary care university hospital. PATIENTS: All consecutive pediatric intensive care unit patients <18 yrs of age with suspected ventilator-associated pneumonia. INTERVENTIONS: For all patients, the following diagnostic methods were compared: 1) clinical data using Centers for Disease Control criteria; 2) blind protected bronchoalveolar lavage, evaluating quantitative cultures, bacterial index of >5, Gram stain, and presence of intracellular bacteria; and 3) nonquantitative cultures of endotracheal secretions. The reference standard used was clinical judgment of three independent experts (Delphi method) who retrospectively established by consensus the presence of ventilator-associated pneumonia based on clinical, microbiological, and radiologic data. Concordance between each diagnostic method and the reference standard was evaluated by concordance percentage and kappa score. Validity was evaluated using sensitivity, specificity, positive predictive value, negative predictive value, and global value. RESULTS: A total of 30 patients were included in the study. According to the reference standard, ventilator-associated pneumonia occurred in 10 of 30 patients (33%). Bacterial index of >5 in bronchoalveolar secretions showed the best concordance compared with the reference standard (concordance, 83%; kappa, 0.61). Bacterial index of >5 also showed the best validity (sensitivity, 78%; specificity, 86%; positive predictive value, 70%; negative predictive value, 90%; global value, 90%). Intracellular bacteria and Gram stain from bronchoalveolar secretions were very specific (95% and 81%, respectively) but not sensitive (30% and 50%, respectively). Clinical criteria and endotracheal cultures were very sensitive (100% and 90%, respectively) but poorly specific (15% and 40%, respectively). CONCLUSION: Our data show that the most reliable diagnostic method for ventilator-associated pneumonia is a bacterial index of >5, using blind protected bronchoalveolar lavage. Further studies should evaluate the validity of all these methods according to the gold standard (autopsy).

Bronchoalveolar Lavage Fluid↗

PubMed2002

Reproducibility of blind protected bronchoalveolar lavage in mechanically ventilated children.

Blind protected bronchoalveolar lavage (BAL) could be an interesting tool in the diagnosis of ventilator-associated pneumonia in intubated children, but its reproducibility has never been evaluated. This study evaluates the reproducibility, feasibility, and safety of blind protected BAL in mechanically ventilated children. Two blind protected BAL were done, at a 2-hour interval, in 30 patients. The reproducibility of microbiologic and cytologic results was studied. A total of 60 BALs was analyzed. Bacterial growth was present in 26 of 60 BAL (43%). Reproducibility for the presence of bacteria on quantitative cultures was excellent (concordance, 93%; kappa [kappa], 0.86). Concordance for the type of bacteria isolated was 86% and for the number of bacteria was 79%. Reproducibility for the presence of neutrophils containing bacteria was perfect (concordance, 100%; kappa, 1) although only a few BALs had a positive result (8/60). Blind protected BAL was feasible in all patients and all samples were considered adequate for analysis. Complications were mostly benign and transitory except in two cases: one pneumothorax and one significant increase in intracranial pressure. Overall, blind protected BAL is a reproducible test in mechanically ventilated children, is easily feasible, and is usually well tolerated.

Adolescent↗

PubMed2002

Emerging measurement and statistical methods in physical activity research.

Although many studies have attempted to identify mediators and moderators of changes in physical activity involvement, the literature is inconclusive regarding which variable(s) relate to physical activity behavior change. The Cooper 2001 Conference series dedicated a session to discussing measurement and statistical methods that could contribute to advancing this research agenda. This article focuses on four such methodologic approaches: qualitative; psychometric; latent-variable, structural equation modeling; and multilevel modeling. The article presents a brief overview of these methods and discusses potential advantages and limitations of using them.

Factor Analysis, Statistical↗