TABLE 1.

CHARACTERISTICS OF STUDY SUBJECTS

	MZ Twins	DZ Twins	Siblings	Combined DZ Twins/Siblings*
Individuals	94 (47 pairs)	20 (10 pairs)	412 (231 pairs)†	149 (79 pairs)‡
Average age ± SD at most recent PFT (range)	20.2 ± 8.2 yrs (7.8–46.7 yr)	17.6 ± 7.1 yrs (10.8–34.5 yrs)	16.8 ± 6.7 yrs (6.8–46.0 yrs)	16.9 ± 6.3 (7.8–39.0 yrs)
Sex
Female	44	7	190	59
Male	50	13	222	90
Pancreatic status§
Insufficient	93	19	368	139
Sufficient	1	1	43	9
Unknown	0	0	1	1
CFTR genotype
ΔF508/ΔF508	56 (59.6%)	10 (50%)	203 (49.3%)	75 (50.3%)
Non-ΔF508 homozygotes	38 (40.4%)	10 (50%)	209 (50.7%)	74 (49.7%)

Definition of abbreviations: DZ = dizygous; MZ = monozygous; PFT = pulmonary function testing.

^*Same-sex DZ twins and same-sex siblings with fewer than 3 years' difference in age.

^†Fourteen families with three affected children (counted as three pairs), one family with four affected children (counted as six pairs).

^‡Three families with three affected children (counted as three pairs).

^§Physician-diagnosed pancreatic insufficiency or individual taking supplemental pancreatic enzymes.