Approaches to investigating clusters: By example, childhood leukaemia near Sellafield

Summary There is occasionally concern about suspected clusters of disease in geographically localised areas among members of the general public or other groups. These occurrences need a systematic approach to their investigation. Such an approach needs to consider the definition and characteristics of the cluster and of the putative environmental cause for concern. Depending on the outcome of these considerations there will be different actions, possibly involving epidemiological studies. The necessary components of the approach and resulting actions are outlined in this paper, and illustrated by the example of childhood leukaemia rates around the Sellafield nuclear plant.

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Das Vorgehen bei ungewöhnlichen Krankheitshäufungen (Clusters), dargestellt am Beispiel der Häufung von Kindheitsleukämien von Sellafield

Zusammenfassung Clusters von Krankheitsfällen können in der Bevölkerung grosse Besorgnis verursachen. Wie geht der damit konfrontierte Epidemiologe am besten vor? Es wird ein systematisches Vorgehen in Stufen vorgeschlagen, von der Überprüfung der Diagnosen und der Abgrenzung des Clusters bis zur allfälligen Planung von epidemiologischen Studien. Die einzelnen Schritte werden anhand der Häufung von Kindheitsleukämien im Umfeld von Sellafield dargestellt.

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Investigations de «clusters»: Les leucémies infantiles dans la région de Sellafield comme exemple

Résumé Les «clusters» de maladie peuvent être à l'origine d'une préoccupation considérable dans la population. Quelle peut être la réaction la plus appropriée de l'épidémiologue? Une approche systématique est présentée dans cet article, depuis la caractérisation du «cluster» jusqu' à la planification d'études épidémiologiques éventuelles. Chacun de ces pas est illustré par l'exemple concret d'une situation similaire survenue dans la région de Sellafield à propos de l'accroissement des leucémies infantiles autour de l'usine de retraitement de produits nucléaires.

     

Surface shield: device to reduce personnel radiation exposure

A simple device is described that can reduce personnel exposure from scatter radiation by up to 75%. The device consists of an oblong piece of shielding (0.75-mm lead equivalent) that is taped to the side of the patient during percutaneous renal stone removal and other interventional procedures. Contrary to other shields and barriers, this does not interfere with access to the patient. Scatter exposure data from phantom studies are presented and the rationale for surface shielding discussed.     

Influence of exposure patterns of nitrogen dioxide and modifications by ozone on susceptibility to bacterial infectious disease in mice

The nitrogen dioxide (NO2) diurnal cycle found in urban communities usually consists of a low basal concentration upon which are superimposed higher concentration peaks or spikes of short duration. Various components of this environmental exposure mode were examined to assess effects of urban exposure profiles on susceptibility to infectious pulmonary disease. Mice were exposed to NO2 peaks of 4.5 ppm for 1, 3.5, or 7 h, challenged with Streptococcus sp. either immediately or 18 h postexposure, and then observed for mortality. When the streptococcal challenges were immediately after NO2 exposure, the mortality rate was directly related to the length of peak exposure, whether or not a basal exposure was used, and all peak lengths significantly increased mortality. When the challenge was delayed for 18 h after the peak exposure, spiked exposures of 3.5 and 7 h increased mortality to the same degree. If a 1-h peak exposure to 4.5 ppm was superimposed twice daily upon a continuous basal NO2 concentration of 1.5 ppm, there was a suggestive trend toward increased mortality near the end of the second week of exposure when challenge occurred immediately after the morning spike. Studies were also conducted to examine interactions with ozone (O3) and NO2, since urban air typically contains both of these oxidants. Using various combinations of basal and spiked exposure levels of NO2 and O3, synergistic results were obtained for streptococcal-induced mortality.     

CT-guided transthoracic needle biopsy

CT-guided biopsy of pulmonary and mediastinal lesions is safe and effective. It is most valuable in those cases in which fluoroscopic guidance is not possible due to resolution or anatomic consideration. CT guidance permits puncture of lesions as small as 0.5 cm, typically not seen fluoroscopically. Sensitivity of biopsy in malignant lung lesions in our series of 83 cases was 92%. Pneumothorax is the most frequent complication (10–60%) and requires chest tube insertion in 5–15% of patients.     

Fertilization and early embryology: Clonal analysis of growth of the polar trophectoderm in the mouse

The results of experiments in which horseradish peroxidase (HRP)was used to mark single trophectoderm or inner cell mass (ICM)cells in situ in mouse blastocysts have led to the proposalthat growth of the trophectoderm depends on stem cells locatedin the inner cell mass. Thus, the finding that the visual centreof clones formed following labelling of the central polar trophectodermcell in early or expanding blasrtocysts was consistently shiftedtowards or into the mural trophectoderm was attributed to theirdisplacement by ICM-derived cells. However, the frequency withwhich central polar cells were displaced is likely to have beenoverestimated by using the visual centre of descendant clonesas the index of their location. also, the possibility that displacementof central polar cells was an artefact of the marked temporaryinterruption of their cycling that resulted from labelling wasnot discounted. Furthermore, no attempt was made to ascertainwhether cells located elsewhere in the polar trophectoderm alsomoved murally, as expected if there is a general displacementof such cells. In the present study, labelling of either thecentral or a peripheral polar trophectoderm cell with HRP wasachieved without obviously perturbing their subsequent proliferation.Moreover, displacement was assessed by recording the locationof the proximal boundary rather than the visual centre of theresulting clones. Even by this conservative criterion, the majorityof labelled central cells moved towards or into the mural trophectoderm. In marked contrast, however, labelled peripheral polarcells moved murally in only a minority of cases. The remaindereither retained their original position or moved towards ratherthan away from the central polar region. Such an anisotropicpattern of growth of the polar trophec toderm is not readilyexplicable in terms of recruitment of cells from the ICM. Rather,it accords with the view that the polar trophectoderm is a proliferativecentre, and suggests that movement murally of its surplus cellsmay be restricted circuinferentially, possibly through anchorageof the junctional trophectoderm cells that extend processesover the free surface of the ICM.     

Evaluation of a rapid stoolantigen test for the diagnosis of Helicobacter pylori infection in Chinese patients

OBJECTIVE: To evaluate the accuracy of a rapid assay that wasdeveloped to detect Helicobacter pylori antigen in the stool,using the principle of immunochromatography, in the Chinese population. METHODS: Eligible patients without prior treatment of H.pylori were recruited. An in‐house rapid urease test (RUT) andhistology were used as the gold standard. The results of the rapidstool antigen test were compared with the gold standard. RESULTS: Valid rapid stool antigen test results for interpretationwere obtained from 94 consecutive patients (mean age: 52.5, range:22?82 years). Sensitivity, specificity, positive predictivevalue, negative predictive value and accuracy were, respectively, 77.5%,87.0%, 81.6%, 83.9% and 83.0%.The test was easy to perform and results were available within 15 min. CONCLUSION: The rapid stool antigen test using immunochromatography accuratelydiagnoses H. pylori infection in Chinese patients.