The efficiency of each of two methods for monitoring the occurrence of a rare event, the cusum, carried out monthly, and the sets techniques, was assessed by use of simulated datasets. The monthly cusum parameters used in this study were those recommended for monitoring of birth defects in a monthly analysis. The sets technique parameters, recommended for monitoring of low-level epidemics, were adjusted to match the average interval between false alarms to the corresponding values observed for the monthly cusum technique. The results indicate that the relative efficiency of the two techniques depends on the baseline frequency of diagnoses. The sets technique is shown to be more efficient than monthly cusum when the number of cases expected in a year is no greater than five, but less efficient otherwise. In the former case, lengthening the interval between cusum analyses can make the cusum technique more efficient than the sets technique. This possibility deserves further exploration and could affect future recommendations.
Three techniques for disease time-space clustering analysis, those of Knox, Mantel and Ederer-Myers-Mantel, were applied to simulated data so as to study their sensitivities. The simulated data corresponded to three alternative non-null models for the distribution, transmission and development of Hodgkin's disease (HD) which were formulated in accordance with the results of published studies. The results indicate that the three techniques may not be sufficiently sensitive to the clustering in a real data set of HD cases. Therefore, the inconclusive results obtained to date with regard to clustering of HD may be related to the low power of the statistical techniques employed.
Background: There is evidence that the nicotinic α7-acetylcholine receptor (α7-AChR) is involved in the pathophysiology of schizophrenia. Several neurotransmitter receptors, including α7-AChR, have been demonstrated on peripheral blood lymphocytes (PBL) and it has been suggested that these peripheral receptors may reflect corresponding brain receptors. Objective: In this study we compare α7 mRNA expression in PBL between schizophrenia patients and control individuals in order to determine whether any correlation exists between α7 mRNA expression in PBL and severity of schizophrenia. In addition, the isoforms of α7-AChR expressed are identified. Method: Peripheral venous blood samples were collected from individuals with schizophrenia (n = 44) and from healthy subjects (n = 16). Symptomatology and illness severity were assessed using standard clinical psychiatric evaluation scales. RNA was prepared from isolated lymphocytes and DELETE α7 mRNA was measured by RT-PCR. Results: We observed a significantly lower level of α7 mRNA on PBLs of schizophrenia patients incomparison with healthy controls (p < 0.00). A tendency to a negative correlation was noted between the CGI score, reflecting illness severity, and the α7-subunit gene expression. Conclusion: Observations confirm that the α7 mRNA in PBL represents the duplicated α7-AChR gene rather than the classic α7-AChR gene. Our study observations further substantiate the involvement of α7-AChR in the pathophysiology of schizophrenia and, while preliminary, indicate that the α7-AChR may be expressed and be readily measured in the peripheral blood circulation.
SummaryValues recommended for the parameters of the sets technique are presented. These values are more accurate than the ones published earlier. The values are determined so as to enhance the detection of small levels of increase in the rate of a rare event.
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