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

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%)*