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Table 1 Number of approached/participating classes and adolescents in the HELENA study #

From: Main characteristics and participation rate of European adolescents included in the HELENA study

CENTERS Athens Dortmund Ghent Heraklion Lille Pecs Roma Stockholm Vienna Zaragoza
Number of eligible schools in the city 82 55 43 22 40 12 290 25 347 83
Number of schools approached/participating 17/10 14/11 11/9 11/10 13/12 8/7 18/10 14/10 23/13 16/12
Number of classes approached/participating 14/14 23/23 20/19 22/20 19/18 24/14 24/22 25/23 35/19 26/23
Number of adolescents approached in all approached classes 458 603 429 429 538 720 470 645 870 597
Number of adolescents approached in all participating classes/adolescents participating 458/370 603/515 413/347 400/340 508/308 420/401 430/339 535/377 536/427 537/441
Number of adolescents eligible for statistical analysis 321 (70%)* 476 (79%)* 336 (78%)* 284 (66%)* 287 (53%)* 394 (55%)* 304 (65%)* 341 (53%)* 403 (63%)* 382 (64%)*
BLOOD SAMPLE
number of classes approached/participating for blood sample 6/6 8/8 6/6 8/8 8/6 5/5 10/9 8/5 10/7 7/7
number of adolescents approached/participating for blood sample 161/137 155/136 145/125 142/122 177/108 150/141 186/112 150/128 198/125 136/125
Number of adolescents eligible for statistical analysis 104 (65%)* 122 (79%)* 113 (78%)* 104 (85%)* 86 (49%)* 136 (91%)* 101 (55%)* 99 (66%)* 112 (56%)* 112 (82%)*
  1. # Data collected from 2006 to 2007.
  2. * Percentage calculated to reflect ratio of selected adolescents for statistical analysis to adolescents approached in all approached classes.