Table 1

Exposure and analytical sample size

Sample size
Exposure periodPre exposureExposure period
Overall*
 Exposure24769638
 Control603336 765
Site 1: ENT endoscope exposureJanuary 2008–February 2009561675
Control sites13451508
Site 2: ENT endoscope exposureSeptember 2002–January 2009138378
Control sites6371089
Site 3: colonoscope exposureApril 2003–December 2008NA6226
Controls sitesNA12 739
Site 4: colonoscope exposureMay 2004–February 200920126189
Control sites11 59426 499
Site 5: dental exposureFebruary 2009–March 201017771794
Control sites40515083
Site 6: dental exposureJanuary 1992–July 2010NA565
Control sitesNA16 346

  • *Total excludes site 4.

  • ENT, ear, nose and throat; NA, not available given exposure period and available data.