Table 1.
Study Sample Characteristics
| Stage 1 Samples (Discovery)
|
Stage 2 Samples (Validation)
|
|||||||
|---|---|---|---|---|---|---|---|---|
| Denmark | Denmark | United States | Sweden | |||||
| Cases (n=1001) | Controls (n=2371) | Cases (n=796) | Controls (n=879) | Cases (n=738) | Controls (n=697) | Cases (n=129) | Controls (n=742) | |
| Boys, No. (%) | 826 (83) | 1276 (54) | 666 (84) | 412 (47) | 619 (84) | 584 (84) | 110 (85) | 395 (54)a |
| Year of birth, range | 1987–2008 | 1986–2008 | 1983–2010 | 1998–2003 | 1998–2005 | 1998–2005 | 1958–2011 | NAb |
| Year of birth, mean (SD) | 1996 (6) | 2001 (3) | 1990 (7) | 2000 (1) | 2001 (2) | 2001 (2) | 1998 (6) | NAb |
| Maternal Age, mean (SD), years | 28 (5) | 29 (5) | 28 (5) | 24 (2) | 28 (6) | 30 (6) | 28 (5)c | NA |
| Season of birth, No. (%) | ||||||||
| Winter | 247 (25) | 562 (24) | 170 (21) | 192 (22) | 165 (22) | 193 (28) | 34 (26) | |
| Spring | 246 (25) | 566 (24) | 184 (23) | 207 (24) | 196 (27) | 178 (26) | 26 (20) | |
| Summer | 280 (28) | 635 (27) | 242 (30) | 249 (28) | 194 (26) | 170 (24) | 30 (23) | NA |
| Autumn | 228 (23) | 608 (26) | 200 (25) | 231 (26) | 183 (25) | 156 (22) | 39 (30) | |
| Age at diagnosis, mean (SD), days | 37 (18)d | - | 39 (22) | - | NA | - | 41 (19)e | - |
| Case definition | Surgery code for pyloromyotomy (ICD-8 codes 41840, 41841, 44100 up through December 1995; ICD-10 codes KJDH60, KJDH61 from January 1, 1996) in the Danish National Patient Register. | Surgery code for pyloromyotomy (ICD-8 codes 41840, 41841, 44100 up through December 1995; ICD-10 codes KJDH60, KJDH61 from January 1, 1996) in the Danish National Patient Register. | British Pediatric Association code for pyloric stenosis (750.510) in New York State Congenital Malformations Registry. | Pyloromyotomy registered in pediatric surgery clinic records. | ||||
| Sample Types (n) | DBSS (1001) | DBSS (961); Buffy coat (1410) | DBSS (796) | DBSS (879) | DBSS (738) | DBSS (697) | Whole blood (129) | Whole blood (380); Placenta (362) |
| Genotyping Platform | Illumina Human 660W-Quadv1_A Bead Array | Centaurus (Nanogen) or TaqMan (Applied Biosystems) | KASP (LGC Genomics) | TaqMan (Applied Biosystems) | ||||
Abbreviations: DBSS, Dried Blood Spot Samples; ICD-8, International Statistical Classification of Diseases, Eighth Revision; ICD-10, International Statistical Classification of Diseases, Tenth Revision; NA, data not available.
a
Sex was missing for 14 of the Swedish controls. The percentage is based on the 728 participants with sex data available.
b
362 of the Swedish controls were infants born in 2006; the remaining 380 were middle aged anonymous blood donors for whom year of birth was not available.
c
Based on 96 cases with maternal age information available.
d
Based on 996 cases with age at diagnosis information available.
e
Based on 101 cases with age at diagnosis information available.